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Reverse Osmosis Filters


  1. Reverse Osmosis water and Orchids; aquarium water
    by (Richard Sexton) (Wed, 22 Jun 1994)
  2. R/O Waste to Product Ratio
    by mwh-at-dymaxion.Eng.Sun.COM (Mark Hapner) (20 Jun 1994)
  3. Pure Water
    by (Tim Miller) (25 Aug 92)
  4. revere osmose information
    by (Matthew William Mengerink) (23 Apr 1995)
  5. Recovery and Rejection Calculations of Reverse Osmosis (RO) systems
    by Ken Holliday <> (Sun, 05 Nov 95)
  6. R/O water dangerous?
    by "James Purchase" <jpp/> (Wed, 22 Jan 1997)
  7. importance of r/o & pH meter
    by Randy or Deb Carey <carey/> (Fri, 28 Nov 1997)
  8. Random RO information...
    by miller/ (Tim Miller) (3 Feb 1998)
  9. Water-Treatment (Reverse-Osmosis Reccomendations Needed)
    by recker/blizzard.Eng.Sun.COM (John Recker) (6 Dec 91)
  10. You want an RO unit....get one of these
    by bowden/ (John W. Bowden) (Fri, 20 Mar 1992)
  11. Complete RO system $169
    by gb/ (Gary Bishop) (9 Apr 92)
  12. Choosing an RO unit
    by pprior/ (Paul A Prior) (Thu, 25 Mar 1993)
  13. [M] Should I buy a RO or DI filter
    by Steve Ghera <Ghera_SJ/> (22 Apr 94)
  14. Skimmer/R.O. Question
    by mwh/dymaxion.Eng.Sun.COM (Mark Hapner) (11 Mar 1994)
  15. pH of RO water (was APD V3 #749)
    by George Slusarczuk <yurko/> (Sun, 03 Jan 1999)
  16. pH of RO water
    by George Slusarczuk <yurko/> (Mon, 04 Jan 1999)
  17. reducing water hardness for breeding discus
    by IDMiamiBob/ (Sun, 24 Jan 1999)
  18. R.O. UNIT
    by Tim Ellis <timellis/> (Mon, 22 Mar 1999)
  19. Increasing RO production.
    by The Eng Family <engfam/> (Mon, 25 Oct 1999)
  20. Increasing RO production.
    by The Eng Family <engfam/> (Wed, 27 Oct 1999)
  21. R/O Units
    by WnyZman/ (Sun, 11 Jun 2000)
  22. R/O Units
    by IDMiamiBob/ (Sun, 11 Jun 2000)
  23. RO Water
    by "Roger S. Miller" <rgrmill/> (Thu, 20 Apr 2000)
  24. DIY deionizer
    by Wright Huntley <jwwiii/> (Fri, 02 Nov 2001)

Reverse Osmosis water and Orchids; aquarium water

by (Richard Sexton)
Date: Wed, 22 Jun 1994
Newsgroup: rec.gardens,rec.gardens.orchids,rec.arts.bonsai,sci.aquaria,alt.aquaria,rec.aqu

[This article has a rather bizarre crossposting, although it's
actually relevant to all groups concerned. Should you choose
to follow-up this article you will need to set the newsgroups
line manually to the appropriate group(s)]

Ed asked this question on the orchids mailing list (which from where I
sit has 10X the volume of rec.gardens.orchids) so as well as responding
to it there I'm sticking it in rec.gardens.orchids.

Rec.gardens and rec.arts.bonsai are getting it because of the use
of dirst aquarium water as a fertilizer which people may not know
about, the aquaria groups are getting it for the same reason.

>Date: Wed, 22 Jun 1994 07:32:32 -0700 (PDT)
>From: Ed Wong <>
>Subject: [1699] Re: Orchids List Digest - Volume [190]
>Regarding Misting and Reverse Osmosis Water
>To the Assembled Brain Trust,
>Does anyone have any experience or thoughts on using Reverse Osmosis 
>Water in a misting system.  (Reverse Osmosis is a filter system that 
>yields something on the order of 99% pure water)  Aside from reduced wear 
>on the nozzles, I would expect less hard water deposits on the plants.
>Los Angeles
I have plenty of experience using reverse osmosis water in Los Angeles!
When I lived there (3 years ago, for 10 years) I used to keep and breed
killifish, a rather specialized (and very pretty) group of tropical
fish. Some of them are rather demanding, and many killi hobbyists
have home Reverse Osmosis setups.
A reverse osmosis filter works by passing water, under pressure,
through a membrane. Somehow this removes a large number of things
in the water, like calcium, magnesium, lead, PCB's etc. It does not
remove chlorine/chloramine, although many people who don't know 
any better will tell you it will.
How much ``stuff'' is removed from the water by an RO filter is a 
function of how tigtly the membrane is wrapped around the core, the
tighter it's wrapped, the purer the water, but the less water you get.
For every gallon of RO water, it dumps about 9 gallons of ``liquid
rock (LA Tap)'' down the waste water return. If the membrane is
wrapped less tightly around the core you get a higher rate of water
but it's not as pure.
Of intererest to killifans is the calcium and magnesium that make
tapwater (especially LA tapwater) so hard. Out of the tap it's
around 800 ppm. My membrane was wound fairly loosly, and I got
about 15 gallons per day of 50 - 100 ppm water. This suited
me fine, as, if if came out really pure (10 ppm) I'd need to
cut it with tapwater because water that pure has no buffering
ability and can take quick and drastic pH shifts.
I did keep orchids when I was in LA - just a few, I was not
very serious about them - and I watered them with waste auarium
water, which all plants seem to love - the dirtier the better
We used to hve friends who would come over once a week with 4
5 gal continers to take home some really dirty aquarium water
for fertilizer for their vegetable garden. They did a little
test and had better results with aquarium water than with 
chemical fertilizers, anyway, I digress.
RO filters are vailable in rates from 5 gal per day to units
than run car washes. Good ones will have a polyester prefilter
to capture bit's of rust and other sediment, and a carbon
postfilter to remove the aforementioend chlorine and chloramine.
Models sold as drinking water oftern have a bladder storage tank, whereas
models sold for fish/plants usually just drain into a bucket.
In the Los Angeles area (Glendale, I believe) there is a fellow,
Ron Harlan who runs ``Back to Nature Filtraton'' who sells RO
units specifically for plants and fish. Ron is (was ? it's been years
since I spoke with him) head of the biology department at Glendale
city college. He really knows his stuff. I just called to verify
his number and discovered he's ``doing inventory'' (which probably
means he's off collecting fish in Peru or Argentina) and will be
closed between June 6 and June 29. The recording mentioned that
if you mentioned the recording you'd get 10% off. Kinda wierd but
usefull I suppose. Anyway, he comes highly reccomended.
When I sed RO water I has zero zip none no da nada white spots
on the plants from carbonate hardness. Now that I'm in toronto
and although the tapwater is only about 350 ppm I DO get white
spots on the plants, espeacially on the Bromeliads, which
get a ``ring around the cup''.


Richard J. Sexton                Masonic order of the MANGO/Gryphon Gang North                  

R/O Waste to Product Ratio

by mwh-at-dymaxion.Eng.Sun.COM (Mark Hapner)
Date: 20 Jun 1994
Newsgroup: sci.aquaria

The waste to product ratio in most R/O units is set using a flow
restrictor in the product line.  Most units are set to operate in the 4
to 5 range.  One factor in deciding what ratio to use is the total
hardness of the feed water.  The higher the hardness the more water
needs to flush the membrane to keep it from clogging.  Most units are
set assuming your water is hard.

If your feed water is soft it is possible to reduce the ratio to the 2
to 3 range.  This can save alot of water.  Check with your R/O vendor
for details.  I recently had Spectrapure adjust my R/O unit after
switching it to softened feed water.  The ratio was reduced from 5+ to
2+ without any major affect on quality (as measured by the TDS

-- Mark Hapner

Pure Water

by (Tim Miller)
Date: 25 Aug 92

After all the years of searching for a DI water guru, I may have become
one if you consider the volume of mail I have been getting from my first

The reason you can drink the RO water that you buy in the grocery store
(or where ever you buy it) is that those machines use cellulose acetate
membranes to perform the reverse osmosis.  They are extremely susceptible
to bacteria, and highly tolerant of chlorine.  So even though they remove 
90-95% of the ionics and all of the colloids, the CA membrane passes
enough of the chlorine to keep the bacteria from growing.  So your "pure"
drinking water still has a few odds and ends left in it.

Cellulose Acetate membranes are "old" technology.  Newer membranes are
thin-film composites, with much higher throughputs and higher rejection
rates (purer product), and higher tolerance of bacteria.  But they have
almost no tolerance for chlorine.  These are the membranes that are in most
medium and large systems.  These systems will have an activated charcoal
filter before the RO to remove the chlorine.  This RO water is highly
unsafe to drink, since there is nothing left to inhibit the growth of
bacteria.  And some really nasty bugs can live in the dark on just water
and carbon based molecules, whether it be plastic or your digestive tract.

Most bottled water is sterilized with ozone, put into the bottle and sealed.
Ozone in water has a 20 minute half-life at room temperature, and the 
ozone that comes out of solution sterilizes the inside-top of the 
container.  By the time you get the bottle home, you have oxygen-rich
sterile water.  So until you break the seal and let bugs in, it stays sterile.

        If anyone wants more ramblings on pure water and how to get the
most gallons for a buck, mail me and I will try to summarize for the group.


revere osmose information

by (Matthew William Mengerink)
Date: 23 Apr 1995
Newsgroup: rec.aquaria

In article <3ndqr1$> erik jan de bos <> writes:
>   i want to buy a reverse osmose for mine Apistogramma but i want to
>   have some practicle in formation about how to use the osmose
>   i don`t nowe enone how has one the water what i want is black water
>   from the Rio Negro in south America 

	To use an RO you simply attach the device to a water hose outlet, and
let the output trickle into some sort of sump.  There are extra devices one can
add to the RO unit to automate the process (automatic turnoff when the sump is
full etc.) and make life more convenient.  These are nice if you are
independantly wealthy ;-)

	The RO has anywhere from 2 to four filters (and perhaps even more).
The two essential ones are the micron membrane and the reverse osmosis 
membrane.  The micron membrane needs to be replaced every 6-8 months depending
on use, and the ro membrane every two years (depending on model of RO and
the local type of water).  Additional filters are activated charcoal pre and
post filtration for removing organic solids and chlorine.

	To simulate the Rio Negro, you can use RO water (if it is even
necessary given you water conditions).  PLEASE make sure that it is necessary
to use RO for this.  Now, w/ the water you have, you can add a phosphate 
buffer (if you don't have lots of plants and bright light (otherwise you 
have an enormous algae problem).  If you do have plants, then there are
some non-phosphate buffers available.  Take down to appropriate pH for the
apistos of your choice.  Now, you have four options from here
	1. Ignore color factor and stop where you are.
	2. Add a blackwater additive (I believe Tetra makes one).
	3. Filter you water through peat (before adjusting pH).
	4. Add some african "driftwood" (actually a root of some tree there).

	Make sure you need the RO!

	Further, spawning some apistos does not demand such particular
attention to water type.  Make sure that the apistos that you have need
this condition to breed.  If you just want this for their well being, or
because you like black water,... just follow one of steps 2-4.

				Matthew Mengerink

---------------------------- "Fish weird me out!" -----------------------------

Recovery and Rejection Calculations of Reverse Osmosis (RO) systems

by Ken Holliday <>
Date: Sun, 05 Nov 95
Newsgroup: rec.gardens, rec.gardens.orchids, rec.arts.bonsai, sci.aquaria

In the last message dated 20 Jun 1994 from Mark Hapner, the first line 
refered to most RO units adjusting for waste to product ratio by the use 
of a restrictor in the product water line.  I believe that his 
information is not quite complete on the RO process.  In the thousands of 
RO units which we have manufactured, the waste line is where you will 
find the flow restrictor (some fixed and others adjustable).  

To calculate this ratio known as "The Recovery" use the following 

Product Water Flow Rate / Feed water Flow Rate x 100 = % Recovery.

Remember that the Feed flow rate is simply the Product Water Flow Rate 
plus the Waste Water Flow Rate.  By restricting the amount of water which 
is flowing to the drain (Waste Water Flow Rate), you will increase the 
recovery of your system.  

NOTE: be careful not to exceed the maximum recovery of the membrane.  The 
SDI (Silt Density Index) of the feed water as well as the Ksp of certain 
consitiuents will govern the recovery which the membrane can be safely 

To calculate the "Percent Rejection" of the unit:

(Feed TDS - Product TDS) / Feed TDS x 100 = % Rejection.

This will tell you the amount of TDS (Total Disolved Solids) which are 
being rejected by the unit.

Hope this helps someone,

Ken Holliday
Commercial/Industrial Sales Manager
Culligan of Canada Ltd.
Mississauga, Ontario, Canada

R/O water dangerous?

by "James Purchase" <jpp/>
Date: Wed, 22 Jan 1997

George and others,

I don't know if I would refer to myself as an expert, but I have had a TFC
(Thin Film Composite) Reverse Osmosis filter for a number of years and can
vouch for the fact that it CAN be dangerous to drink (and I suppose, use in
an aquarium).

My R/O unit is mounted on the wall next to the kitchen sink and is not
permanently plumbed into the waterline - it uses an attachment to snap onto
the faucet. To store the water temporarily, I keep an empty 15 gallon,
all-glass aquarium on the counter, shoved back in a corner, to hold the
water until I need it. The TFC unit, as another poster has noted, removes
all of the chlorine from the water prior to sending it throught the
membrane. The R/O water from the TFC type unit is generally purer than that
produced by the CTA units but for long term storage (and especially for
human consumption) should be kept refrigerated. Without any chlorine in the
water there are enough residual minerals left in the water to allow for the
growth of bacteria.

This past summer I was out of town for a month on vacation. I had left
about 10 gallons of R/O water in the holding tank when I left (it is
covered). When I returned, the tank had a very noticeable layer of slime on
the inside glass. It wasn't algae (it was white) and I didn't wait around
to figure out what else it might be - I bleached the tank. There ARE
bacteria that can even survive chlorine bleach so I would advise people to
be careful. I have no idea if this stuff was dangerous, I certainly wasn't
going to use either myself or my fish as test subjects.

B.T.W., while I was away I had removed the membrane from the filter unit,
sealed in wet in a plastic bag and put it in the refirigerator to avoid any
possibility of bacteria growing on the menbrane.

For me and my fish, Reverse Osmosis water has been a godsend, but it has to
be handled properly (storage in sterile, opague containers).

James Purchase
Toronto, Ontario  

importance of r/o & pH meter

by Randy or Deb Carey <carey/>
Date: Fri, 28 Nov 1997
To: apisto/

The past month has taught me the importance of r/o water and a good pH

For months my spawns had slowed down to almost non-existant.  Then I
decided to put money into equipment instead of just into fish.  I bought
a new CTA r/o unit and a PinPoint PH meter (chemical tests are a pain).

The meter allowed me to discover that my old r/o unit's product water
was slightly alkaline and buffered more than I thought.  The new unit
now produces water in the high 5's.

In the past four weeks I have successful spawns from four new Apisto's
(including "pandurini"), two African dwarfs (the new Pelvicachromis
sacrimontis and Nanochromis transvestitus), a tetra, and my first ever
Rasbora (perhaps a thousand fry!).  I was excited to see Rasbora going
through the spawning sequence--this is a difficult genus and I had never
seen it from a Rasbora.

Anyway, my point is that investment in the proper equipment will go a
long way toward success.  A serious Apisto keeper/breeder should have an
r/o unit, a reliable pH meter, a refrigerator dedicated to keeping
live/frozen foods, and (of course) reliable heaters/thermometers.


	(back in buisness)

This is the apistogramma mailing list,
For instructions on how to subscribe or unsubscribe or get help,
Search for "Apistogramma Mailing List Archives"!

Random RO information...

by miller/ (Tim Miller)
Date: 3 Feb 1998
Newsgroup: sci.aquaria

	Sorry folks, just can't help myself.  Have to put in my two cents worth

	There are two types of RO membranes, Cellulose Acetate (CA)
and Thin Film Composite (TFC).

	TFC has a higher rejection rate and more flux per unit area of
membrane than does CA.

	CA membranes are good culture media to grow bacteria, therefore
CA feedwater should be chlorinated.

	TFC membranes will be damaged by Chlorine, therefore you will need
to pretreat Chlorinated feedwater with activated charcoal to remove the
Chlorine.  Most manufacturers specify less than .1 ppm free Chlorine.

	Both type membranes concentrate ions in the waste water, so feedwater
to any type of RO membrane should be run through a water softener first, to
swap out any sparingly soluble ions for Sodium ions.  In other words, brine
won't precipitate out in an RO membrane like carbonates and other crud found
in tap water.

	A 5 Micron prefilter will extend the life of the RO membrane.  Unless
your tap water is silt-free.   :-)

	Most RO membranes are optimized for 77 degree F feedwater.  Colder
water means less permeate but a higher rejection rate (better water).   Warmer
water means more permeate of lower quality, and anything over 113 F will
damage the membrane.

	Brand-new membranes are shipped in a solution that is both a
bacteria inhibitor and anti-freeze.  RTFM and throw away the permeate
for the prescribed start-up period.

	I can't tell you who makes the best equipment for home use, but
one of my many responsibilities at work is to supervise 2 3000 gallon per day
DeIonized water plants, so I do have some favorite suppliers of somewhat
larger scale equipment.

	Feel free to e-mail questions relating to ultrapure water, but please
realize that answering that e-mail isn't first item on the list of things to
be done.

Tim Miller	Manager Solid State Materials and Devices Laboratories
		School of Electrical and Computer Engineering
		Purdue University
Internet:			 AMPRnet:
"America's one of the finest countries anyone ever stole"   -Bobcat Goldthwait

Water-Treatment (Reverse-Osmosis Reccomendations Needed)

by recker/blizzard.Eng.Sun.COM (John Recker)
Date: 6 Dec 91
Newsgroup: alt.aquaria

In article <> (Ken Koellner) writes:
>In article <> (John Raffensperger Jr.) writes:
>>What kind of small scale purification systems are ther out there to be
>>bought or built?
>I am using the small deionizer from Marine Inverts.  It costs
>about $50.  You can run tap-water through it at about 8gal/hour.
>It is a 2.5" X 18" acrylic tube containing about 1/4gal of mixed
>resin.  It has hose barb fittings.  
>The resin in the unit will probably last me a year.  The only
>way to open the unit is to unscrew the hose barb from the acrylic
>opening about a 3/4" hole.  About two inches of poly fluff then would
>have to be pulled out to get the resin out.  If you like to play with
>PVC pipe, I think a homebuilt unit with their resign would be not
>a pretty but a little bit better.

Ken, are you suggesting that an arrangement like this:

                       ++ XX                         XX++
                       || XX                         XX||
tap water in---->   ---++ XX<-----"poly fluff"------>XX++--- fitered water out->
                    ---++ XX                         XX++--- 
                     ^ || XX        Resin here       XX||
                     | ++ XX                         XX++
                     | -^------------------------------- 
                     |  |           ^
                     |  |           |
                     |  |           +------------ threaded PVC tubing
                     |  |
                     |  +--- threaded end cap
                     +--- fitting to connect to tap line

Would essentially duplicate the filter you have? If so, this would indeed
be pretty cheap as this amount to no more than $15 of PVC tubing and parts.


	John Recker
        ARPA: recker-at-Eng.Sun.Com
        UUCP: {decwrl, hplabs, seismo, ... }!sun!recker
	MaBell: (415)336-7396

You want an RO unit....get one of these

by bowden/ (John W. Bowden)
Date: Fri, 20 Mar 1992
Newsgroup: alt.aquaria,rec.aquaria

Hi folks,
 I've been kicking around the idea of getting an RO unit for a
while now, and I finally broke down and got one.  I got mine
for my south american cichlids.  I had been looking at the 
25gal/day unit that Regal Discus advertised in FAMA but then
I noticed that the manufacturer of the same Spectra-Pure unit
was now advertising.  I called the company up and talked to a
salesman.  He said that i would get the best output rate at 60psi
and 77F water.  Well, my water is about 40F but i have real high
pressure (actual pressure unknown.)  Anyways, my 50gal/day CSP50
puts out about 46 gal/day on my cold water.  The best part is that
the unit cost only $217 with 2nd day shipping.  They tried to sell
me adapters and quick-releases and such but i got these at the 
hardware store.  Total cost for my set-up:

CSP50 RO Unit             $199
35gal garbage can         $ 11
8' of vinyl hose (siphon) $  4
quick-rel connector       $  3
shipping                  $ 18
total                     $235

Now my apistos get to rollick in 1DH water and i still have 
enough money left to buy a new bale of peat! :)

BTW, I have nothing to do with the company other than being a happy

If you want an inexpensive RO unit look in FAMA for Sheridan Bay.
(They are not in the Advertisers index in my FAMAs.)  They run
full-page ads.

John Bowden

Complete RO system $169

by gb/ (Gary Bishop)
Date: 9 Apr 92
Newsgroup: rec.aquaria,alt.aquaria

At the suggestion of some fellow *.aquaria readers I had a CA buddy
purchase a RO system at "Price Club" and ship it to me.  I've
installed it now, and it appears to be working very well.  The fit and
finish are excellent.  The system consists of a sediment filter,
carbon filter, TFC reverse osmosis filter, automatic shutoff, 3 gallon
pressurized storage tank, post storage carbon filter, and an "air gap"
faucet.  This complete system was $169.  This is much cheaper than I
have seen in the aquarium mags.

I haven't measured the output of the system but I'm guessing it is
producing about 12 gallons per day.  The system is manufactured by

Premier Manufactured Systems, Inc.
4737 North 43rd Avenue, Suite 1
Phoenix, Arizona
(602) 931-1977
(800) 752-5582

The fellow on their 800 number was very helpful in talking me through
a minor bug in my system.

We are using the system for our drinking/cooking water, to drive our
icemaker, and to produce water for weekly water changes in our 36
gallon aquarium.  The water tastes much better and I won't have to
make those trips to the grocery store for distilled water.

Also, the latest "Damark" catalog has a similar looking system for
$199.  I have no knowledge of its performance/quality.


Choosing an RO unit

by pprior/ (Paul A Prior)
Date: Thu, 25 Mar 1993
Newsgroup: rec.aquaria,alt.aquaria

In article <ANCONA.93Mar22204035-at-wpi.WPI.EDU> ancona-at-wpi.WPI.EDU (James P Ancona) writes:
>I'm considering buying an RO unit for my 20G mini-reef. I wonder if anyone has
>recommendations on low-cost, low-capacity units. I've seen ads for Spectrapure
>and Sheridan Bay in FAMA. I think I read something a while back here about a
>dispute between the two companies. Anyone know what the story is?

The story was that Sheridan bay was marketing spectrapure's RO units but
allegedly were selling inferior units (cheaper parts) while claiming to
be selling true SpectraPure RO systems.  They are currently in court
fighting it out, as far as I know.
I originally bought my unit from Sheridan bay, but before the time 
period where the alleged problems started (Last october, I believe).
However, I've dealt with SpectraPure since then with regards to other
products.  I would recommend SpectraPure over Sheridan bay as I've had
nothing but A1 service from SpectraPure and the quality is very good. My
interactions with sheridan bay were far less satisfying.
Charles Mitsis is the owner of SpectraPure and is a great guy (at least
he treats his customers well).  Call them and ask a bunch of questions-
I think you'll get honest answers.  

I think prices are roughly the same between the two, though Charles
claims he is using higher quality membranes.  
Whatever you buy, check out the goodies such as drinking water kit
and auto-leveling (SpectraPure is coming out with a new product
which I have been the first to test which is a very nice auto-top-off
system for those with sumps).  Goodies will make your system 
much more enjoyable ;)
RO water makes AWESOME tea! <G>
Good luck

-- 621-8240----------------
Paul A. Prior    Ban anchors, not reef tanks                        | |
3rd year medical student 		                  Check  --=oOo=--
The Ohio State U. College of Medicine                       six!    +  

[M] Should I buy a RO or DI filter

by Steve Ghera <Ghera_SJ/>
Date: 22 Apr 94
Newsgroup: rec.aquaria

In article <> Kevin N. 
Carpenter, writes:
>I recommend one from SpectraPure.

I bought a SpectraPure as well.  It is a 15 gal. per day TFC RO AND 
DI.  I paid just over $200 for it (think) about 1 year ago.  Because 
of the nature of my feed water, I spent my DI cartridge(s) quickly.  
One of the "top guns" at SpectraPure worked very close with me to 
identify the problem by assaying my feed and product water.  They 
helped with some other things too, but I won't go into it because 
I'm already sounding like a commercial  (sorry folks).  Anyway, I 
use my 15gpd to support a 20gal reef and a 135gal reef.  

TFC or CTA:  Here's what I learned at a conference on water purity

                      TFC                          CTA
Meaning        Thin Film Composite           Cellulose Tri? Acetate

Composition    Polyamide                     cellulose acetate

Advantages     good silica rejection         chloride tolerant
                                             lower price

Skimmer/R.O. Question

by mwh/dymaxion.Eng.Sun.COM (Mark Hapner)
Date: 11 Mar 1994
Newsgroup: rec.aquaria

I use an TFC RO/DI filter.  In my area their is a lot of nitrate (20
ppm +) and silicate in the water.  I found that small amounts of
nitrate (~ 4 ppm) made it through the RO unit.  Since a DI canister can
easily be added to the output of an RO unit you should probably see
what the RO does for you before adding DI.

Some tips if you add a DI are that it works better if you reverse the
flow (connect the output side of the RO to the output side of the DI
cannister).  Also, don't use the first 5 minutes or so output from the
RO.  This first water has much more stuff in it and will exhaust your
DI quicker.  These tips are straight from the mouth of the Spectrapure

-- Mark Hapner

pH of RO water (was APD V3 #749)

by George Slusarczuk <yurko/>
Date: Sun, 03 Jan 1999

Hello Michael,

You are absolutely right! Even among chemists it is a very little known
fact, that the pH of distilled (and RO) water can not be measured. Let
me correct that: It CAN be measured, but the value is meaningless! (That
does NOT mean that distilled water has "no pH" -- just that we can not
mesure it using methods available to a hobbyist -- and that includes
"research grade" electronic pH meters!) 

I know of only one commonly available reference (the ASTM volume on
water) where this is spelled out in plain English (if only in a
footnote). I will not go into the technical reasons for it.

The pH of RO water probably will not be the same as that of starting
water, because the exclusion of ions by the RO membrane is not uniform
accross the periodic table and the residual ionic equilibrium will be
different from that in the source water. But, as you mentioned, the RO
water is not buffered, so it really does not matter: anything added to
it -- fish, plants, water, etc -- will change its pH.



> I think someone on one of the saltwater newsgroups explained that
> measuring the pH of RO water is almost impossible because there is so
> little in it.  Because it has basically no buffering the pH is very
> changeable and letting it equilbrate with the air will probably affect it.
> True however that the pure RO out of the filter would have the same pH as
> the tap going in.  BUt you can change that pH very easily due to no
> buffering.  Then add the buffering and you have the pH you want with the
> hardness, but no bad guys.
> This is a simple way of putting it but basically correct.  If someone
> would like to add please feel free as I am no expert.

pH of RO water

by George Slusarczuk <yurko/>
Date: Mon, 04 Jan 1999

Hello Joseph,

You are, obviously, right that the dissociation constant of pure water
is 10^-14. But do you think that a *hobbyist* can determine such a
dissociation constant in the fish-room? I don't think so!

As I mentioned in my original post, The ASTM volume on water (I think
that it is volume 18 A & B, but am not certain) in the section on
measuring pH, gives that warning about measuring pH of pure water. Right
now I don't have access to that work, so can not cite the exact page
reference. The classic reference is Clark's "Determination of Hydrogen
Ions", from the 1920's.

If we take a medium-grade distilled water, resistivity of, say, 1 megohm
or better, then in a colorimetric determination one drop of an indicator
solution will be the dominant source of hydrogen ions. You will get a
measurement, but it will be that of the resulting diluted indicator
solution, not of the original water.

An electronic pH meter is just a high impedance Volt meter. If the
resistance of the medium is too high, and one is using a *glass*
electrode, (not quinhydrone/sat. calomel half-cells) -- the reading will
drift -- because the instrument can not reliably measure the 59
mV/decade that it is required to do, to measure pH. This is easily
provable, if one has access to *fresh* (without dissolved CO2) 10 megohm
(or better) water then the drift is very obvious. (The quinhydrone/sat.
calomel half-cells are not something that a hobbyist would want to try

I know of one way to circumvent this problem but, again, that is not
something a hobbyist should try in his/her fishroom (because of danger
of contamination and subsequent false measurements): Per 25 mL of sample
add 1 drop of a 10 mM KCl solution of 99.9999% (6N) purity, prepared in
an acid-washed Teflon volumetric flask, using 10 megohm (or better)
water. It will lower the resistivity sufficiently, that a "research
grade" (very high impedance) pH meter, equipped with a quality glass
electrode, will be able to measure it with some assurance of accuracy
and precision.

Hope this explains it somewhat.



> Date: Mon, 4 Jan 1999 08:43:25 -0500 (EST)
> From: joseph sachleben <>
> Subject: Re: pH of RO water
> George Slusarczuk wrote:
> You are absolutely right! Even among chemists it
> is a very little known fact, that the pH of distilled (and RO) water can
> not be measured. Let me correct that: It CAN be
> measured, but the value is meaningless! (That  does NOT mean that
> distilled water has "no pH" -- just that we can not mesure it using
> methods available to a hobbyist -- and that includes
> "research grade" electronic pH meters!)
> *****************************************************
> Hi George,
> I think this argument is wrong. The pH of "pure water", Distilled
> water not allowed to come into contact with anything that might
> leach into the water, is 7. This is because the disassociation constant
> of water at room temperature is 10^-14. This can be measured. The
> dissociation constant of water can be measured. I'm curious as to
> what the technical problems are that you mention.
> Joe Sachleben

reducing water hardness for breeding discus

by IDMiamiBob/
Date: Sun, 24 Jan 1999
To: apisto/

In a message dated 1/24/99 8:04:47 PM Mountain Standard Time,

> No method of reducing hardness is cheap.   Ion exchange (commercial water
>  softener) is your best bet.  Most cichlids tolerate a trace of salt ok.
>  Discus are an exception.

Just as an addendum to Dave's suggestion, be careful what kind of "deionizer"
you get.  Some are merely "water softeners" which exchange the Calcium and
Magnesium ions for Sodium, causing conductivity to rise, and this is the
measureable symptom of the total dissolved solids that discus really are
sensitive to.  Call around and check a number of sources.  Several deionizers
are available which work in two steps, replacing the + ions with H+ and the
negative ions with OH - .  Try your Culligan man, or checkout the KATI-ANI
unit at Pet Warehouse.  Lots of people use RO, but I'm not sold on its
economy.  It ends up dumping a significant amount of water back to the sewer,
unless you also have africans, which I'm guessing might enjoy the high mineral
content of this stuff.  If you live in the Western US where water is at a
premium, RO is a bad choice, but even in LA and Phoenix, most people continue
to use this method.

Now, don't get your dander up folks.  This is my viewpoint, and I think this
is not the best choice for around here.  You guys are free to do it as you see

Bob Dixon

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by Tim Ellis <timellis/>
Date: Mon, 22 Mar 1999
To: apisto/

I have to agree with David. The Spectrapure is a much better unit. I have had my
50 gallon a day for over a year now and no complaints. I can tell you the Kent
unit has a knuckle buster of a wrench. I should also add that the key to long
membrane life is to change the carbon and particle filters at least every 6

My 2 cents


David Sanchez wrote:

> Yes! I use mine for drinking water and for my fridge. Spectapure
> partsb are also readily available. check out their web site
> ---Edison Yap <> wrote:
> >
> > Can the Spectapure line or any Fish Quality R.O. Unit able to
> produce water
> > that is good for human consumption?
> >
> >
> > At 05:56 AM 3/22/99 -0800, you wrote:
> > >
> > >
> > >Don't bother with Kent Marine in my opinion it's a toy. I highly
> > >reccomend the Spectapure line of RO sytems. With Spectapure you get a
> > >much better quality membrane that will give you water in the acidic
> > >values right away. Before I moved to Florida I was using an RO and I
> > >have over the years tested the quality of a few brands. A couple of
> > >years ago for a reef tank I purchased the Spectapure and the results
> > >have been far superior. I have a few guys in my local club using RO
> > >systems and they have to mess with the Ph two of them use kent
> Marine.
> > >Anyway just my 2 cents.
> > >
> > >
> > >---Vern Wensley <> wrote:
> > >>
> > >> Hi Marco.Have you thought about useing a deionizer?I have used the
> > >Aquarium
> > >> Pharmaceuticals tap water purifier with great success.It is rated
> > >for 50 to
> > >> 150 gallons of deionized water,but I can get twice that since my
> > >water is so
> > >> soft already.I only used it for those ph 5 and under fish which
> > >makes it
> > >> last a long time before you have to replace the cartridge.The good
> > >thing
> > >> about it is there is no waste and you can make water at any
> > >want
> > >> .Just add the right amount of electro-right and you have water you
> > >can use
> > >> right away.
> > >> Vern
> > >>
> > >> -----Original Message-----
> > >> From: Marco Lacerda <>
> > >> To: apisto-list <>
> > >> Date: March 22, 1999 3:54 AM
> > >> Subject: R.O. UNIT
> > >>
> > >>
> > >> >I'm trying to start using a R.O. unit in order to get softer
> water,
> > >as
> > >> >specially blackwater Apisto species are posing much problem with
> > >their
> > >> >eggs.
> > >> >
> > >> >Tsuh Yang from this list suggested one from Kent Marine, but he
> has
> > >no
> > >> >experience with it.
> > >> >Does anybody has experience with "Kent Marine Full-Size R.O.
> unit 100
> > >> >gallons per day"?
> > >> >Or another unit from a different trade?
> > >> >
> > >> >How should I use the R.O. water? Mixed with normal water? Any
> > >> >suggestion?
> > >> >
> > >> >Cheers.
> > >> >
> > >> >
> > >> >
> > >>
> >
> >>-------------------------------------------------------------------------
> > >> >This is the apistogramma mailing list,
> > >> >For instructions on how to subscribe or unsubscribe or get help,
> > >> >email
> > >> >Search for "Apistogramma Mailing List
> > >> Archives"!
> > >>
> > >>
> > >>
> > >>
> >
> >-------------------------------------------------------------------------
> > >> This is the apistogramma mailing list,
> > >> For instructions on how to subscribe or unsubscribe or get help,
> > >> email
> > >> Search for "Apistogramma Mailing List
> > >Archives"!
> > >>
> > >
> > >==
> > >
> > >David Sanchez
> > >Casselberry, FL
> > >
> > >
> > >_________________________________________________________
> > >Get your free address at
> > >
> > >
> > >
> >
> >-------------------------------------------------------------------------
> > >This is the apistogramma mailing list,
> > >For instructions on how to subscribe or unsubscribe or get help,
> > >email
> > >Search for "Apistogramma Mailing List
> Archives"!
> > >
> >
> >
> >
> >
> -------------------------------------------------------------------------
> > This is the apistogramma mailing list,
> > For instructions on how to subscribe or unsubscribe or get help,
> > email
> > Search for "Apistogramma Mailing List
> Archives"!
> >
> ==
> David Sanchez
> Casselberry, FL
> _________________________________________________________
> Get your free address at
> -------------------------------------------------------------------------
> This is the apistogramma mailing list,
> For instructions on how to subscribe or unsubscribe or get help,
> email
> Search for "Apistogramma Mailing List Archives"!

Increasing RO production.

by The Eng Family <engfam/>
Date: Mon, 25 Oct 1999
To: apisto/


I just recieved this method on increasing RO water production from one of
my marine aquarium lists:

'I came across a neat strategy for increasing the output of RO units, and I
thought I'd pass it on. Tell me if you've heard this one before. Take a 5
gallon bucket, fill it with warm water (or toss in a heater), and run about
50 feet of high pressure turbing from the spigot to the RO unit - coil the
50 ft. length into the bucket of warm water. Voila - a heat exchanger.
Around here where the water is about 45 degrees at 80 psi, this trick
tripled my output...'

I guess this makes sense since most gpd rate on ro units are dependent on
water tempurature, water pressure & the amount of solids in the water.
SpectraPure rates their units using the following parameters 77 degree
water, 60 psi and 500 TDS.  So I guess if you change any of these (temp &
pressure up and tds down) water production will increase.  Just thought I'd

Victor Eng					Vancouver, British Columbia, Canada

Increasing RO production.

by The Eng Family <engfam/>
Date: Wed, 27 Oct 1999

Hi George,

This is the response that I recieved from the tech reps at SpectraPure:

'Thanks for sharing the idea. We have heard of several similar solutions,
including (After doing what you have done) returning the waste water to the
container to capture more of the BTU's.  The Purity will drop ever so
slightly, less than 1%.'

So I guess that tempuratures over 77 degrees (since this is the baseline)
will cause some degrade in the quality of the ro water output.  No respones
from Kent yet.

p.s. I was mistaken about the water purity of RO units, it is not 99%+ but
they remove over 98% of all ionic impurities and over 95% of organic

Victor Eng					Vancouver, British Columbia, Canada

R/O Units

by WnyZman/
Date: Sun, 11 Jun 2000
To: apisto/

I always enjoy the comments regarding RO "WASTE" water! I hope by using that 
word "waste" you are not dumping it out and losing it. I have a unit that 
produces 25 gallons per day with "non-RO" water at 125 gallons ratio for 
about seven years now. I maintain 80 tanks with an average of about 15 
gallons. The RO water is used only for breeding Apistos and all the other 
water is used for all other tanks. When I sell Apisto's to the local store, 
they are in regular tap "waste" water to avoid stress as I know the store 
doesn't use it's RO water for the sales tanks. At least 75% of my tanks use 
the so-called waste water. My tap water is 170ppm and the waste water is 
still 170ppm. There is never any added hardness in any RO system; that's what 
the filters are for. I actually keep 10 to 15 gallons of that water in 
1-gallon milk type containers for all our cooking needs and it makes great 
coffee! Why the words "waste water" are used, I'll never know. If you use the 
water from your tap, why wouldn't you use this water where all the small 
unseen particales are removed and it's a lot purer?

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R/O Units

by IDMiamiBob/
Date: Sun, 11 Jun 2000
To: apisto/

Z-man writes:

> I always enjoy the comments regarding RO "WASTE" water! I hope by using 
>  word "waste" you are not dumping it out and losing it. I have a unit that 
>  produces 25 gallons per day with "non-RO" water at 125 gallons ratio for 
>  about seven years now. I maintain 80 tanks with an average of about 15 
>  gallons. The RO water is used only for breeding Apistos and all the other 
>  water is used for all other tanks. When I sell Apisto's to the local 
>  they are in regular tap "waste" water to avoid stress as I know the store 
>  doesn't use it's RO water for the sales tanks. At least 75% of my tanks 
>  the so-called waste water. My tap water is 170ppm and the waste water is 
>  still 170ppm. There is never any added hardness in any RO system; that's 
> what 
>  the filters are for. I actually keep 10 to 15 gallons of that water in 
>  1-gallon milk type containers for all our cooking needs and it makes great 
>  coffee! Why the words "waste water" are used, I'll never know. If you use 
> the 
>  water from your tap, why wouldn't you use this water where all the small 
>  unseen particales are removed and it's a lot purer?

Don makes a good point here.  Most of the people who are tossing the "waste 
water" out are simply lacking a little ingenuity.  If you live in those areas 
of the Southwest US where the water is rock-hard, and also extremely scarce, 
then you could put a storage tank in and pump it out onto the lawn.  The 
added expense would pay for itself in lower water bills over a few years.  
You could also add rift-lake cichlids to your fish room, and the hard stuff 
would already be ideal without the addition of salts.  It would be hard to 
use it from the tap, but there are other means of employing it.  If you live 
east of the Mississippi, or in the Northwest rainforest, you may not 
understand and appreciate what a truly precious commodity fresh water is.  
Here in Idaho, more lawyers make their living from "Water Rights Law" than 
you can imagine.

Bob Dixon

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RO Water

by "Roger S. Miller" <rgrmill/>
Date: Thu, 20 Apr 2000

On Thu, 20 Apr 2000, Blendia Nawrocki wrote:
> Where can I find your recipe for reconstituting RO water.  I am using RO-DI
> water in my planted 125 Gal tank.  I have been adding some of my well water,
> it has a lot of silica and causes a lot of brown film if I get too much.  I
> need to change the cartridges now.


I pulled the formula from the original letter.  It follows.  The original
letter was message 22 from August, 1999.  This formula is a correction to
a formula that I slapped together for an earlier post.

People have reported problems getting the calcium carbonate to dissolve,
so using this formula might take some patience.  You may want to go back
to the original letter and some of the earlier conversation to get a more
complete background on the formula.

You should be able to get all of these ingredients at a supermarket.  
Epson's salt and baking soda are sold under those names. Calcium carbonate
comes from tablets sold as dietary supplements; use tablets that contain
calcium carbonate and nothing else.  Potassium chloride is sold as a salt
substitute.  Morton's Salt Substitute for salt free diets is nearly pure
potassium chloride.  You can also buy it at nurseries under the name of
muriate of potash or potassium chloride.

For example, if you want to reconstitute 50 gallons of RO water you would
take four and a half 600 mg calcium tablets, crush them and stir them into
the water.  Also, with a 1/4 teaspoon measuring spoon, measure out and mix
in six and a half 1/4 teaspoon measures of epson's salt, four and a half
1/4 teaspoon measures of baking soda and three 1/4 teaspoon measures of
potassium chloride.

To mix 25 gallons you would use half that much, and so on. 

Happy stirring,

Roger Miller


 Chemical                dose/           dose/           measurement
                         100 liters      50 gallons      unit

 epson's salt            3.5             6.5             1/4 teaspoons
 calcium carbonate       2.5             4.5             600 mg tablet
 baking soda             2.5             4.5             1/4 teaspoons
 potassium chloride      1.5             3               1/4 teaspoons

The composition (after the pH drops) should be

                         dose/           dose/           measurement
                         100 liters      50 gallons      units

 calcium                 15.0            14.3           mg/l
 magnesium                4.7             4.6           mg/l
 sodium                   8.9             8.5           mg/l
 potassium               11.8            12.4           mg/l
 bicarbonate             69.4            66.0           mg/l
 sulfate                 18.4            18.0           mg/l
 chloride                10.7            11.3           mg/l

 general hardness         3.2             3.1           degrees
                         57.1            55.0           ppm as CaCO3
 alkalinity               3.2             3.0           degrees
                         56.9            54.1           ppm as CaCO3
 Na/(Ca+Mg+K)            0.27            0.26           molar ratio
 total dissolved solids  79.8            78.9           mg/l

DIY deionizer

by Wright Huntley <jwwiii/>
Date: Fri, 02 Nov 2001

> Date: Thu, 1 Nov 2001 19:22:17 -0500
> From: "Joe Kopanski" <>
> Subject: DIY deionizer
> I’m looking for advice on building a water deionization system for plant +
> S.A.
> cichlid tanks.

Don't. <g>

> My plan is to create a three-stage system:  1) Granular activated carbon
> (GAC) cartridge, 2) Anion resin, 3) Cation resin.  I plan on using the
> deionzer chambers from Cole-Parmer ($75 each) plus anion and cation resins
> from Spectrapure ($85 and $41/gal respectively).  While the resins are color
> indicating, I’ll also make a resistivity probe for my voltmeter to measure
> water quality.

A $15 pocket tds (total dissolved solids) meter from Hannah Instr. is likelier
to work. Electrolysis and other problems actually make DIY probes rather
difficult to make, unless you have a high-frequency ac Ohmmeter. There are
also cheap little green/red LED in-line indicators for water treatment
monitoring. They change when the water drops out of the megOhm range.

> The main reason I want to build my own DI unit, is so that I can plumb it
> for very easy recharge.  

RO (Reverse Osmosis) units do it without *any* need for recharge, at far, far
lower cost. That's particularly true if you salvage the waste water. I used to
hook mine right into the patio-drip-irrigation system. [It is only a few
percent higher tds than the tap water.]

> I plan on plumbing it so that I valve off each
> deionzer chamber when exhausted and gravity fill with recharge solution.
> After recharge, I’d gravity flush a 5 gal carboy of DI water through the
> chamber, through a marble chip bath, and down my household drain.  While my
> initial cost will be high, I hope to have a portable, high capacity source
> of high purity (< 1 ppm) water that can be recharged cheaply, easily, and
> “forever”.

Provide for major dilution of those recharge solutions, first, for many water
departments now have sewer alarms for anything strong enough to affect the
treatment process. You don't want an environmental swat team in your yard. ;-)

Under current requirements, I'm not sure if that dilution/cleanout water
doesn't approach the waste water produced by efficient, modern RO units! By
coiling 30' of poly inlet tubing in the warm closet, housing my water system,
I turned a 10 GPD system into more like a 30-50 GPD unit, BTW. RO efficiency
goes way up with both pressure and temperature. Attic pre-heating would work
in many homes, too.

Your initial cost is many times what I have paid for RO units. The fuss is
much less with them, while the output water is "safer." 30-50 ppm of tds is
enough to help prevent tds shock and buffer the pH a little bit. IMHO, that's
probably as "pure" as water for fish and plants should ever be.

DI water (and distilled) must always be cut with some tap water (or
reconstituting salts) to be safest for fish or plants, except when used as
simple top-off for evaporatiion, etc. It just creates too much osmotic
pressure drop across the cell membranes, and can even burst them under some
circumstances (like abrupt tds reduction).

> Will my recharge scheme work?

Yep. Sounds OK. Just a lot of extra work and $$$. 

I have arranged two food-safe barrels to receive slow discharges from my RO
and tap waters, with a swamp-cooler cutoff valve on each. [Dry carpet policy.]
Both are fed from a refrigerator-ice-maker saddle valve on the cold line under
a sink. Drip-irrigation valves regulate the flow at each system (and make
annual cartridge changes easy). The newest RO unit came with triple-carbon
filters, and I installed two more in series to the "tap" barrel. A 10 GPD RO
unit let me have ample water for about 150 tanks and smaller containers for
killies. Everything is available at warehouse stores, at reasonable prices.

> I plan on connecting directly to my cold water line and flow control by
> adjusting the cold water faucet.  Will my city water pressure be enough to
> drive a filter housing and two DI chambers in series?  The DI units are
> rated for 15 GPH.

That could be a bit *too* fast for the carbon filter to extract much
chloramine, or even chlorine. I guess that might mean much more frequent
recharges if the ion beds saturate. Slow flow is better (carbon adsorbs huge
amounts of chloramine under slow flow and tap pressures), so intermediate
storage is a must if you have many tanks to service. I just used a waterfall
pump, in either barrel, on the end of 60' of vinyl tubing to reach any tank in
the house. X-10 remote pump switch and hose valve and sprinkler on delivery
end automated the process of tank-to-tank changes. Lifting the pump from one
barrel to the other permitted "mix-and-match" to any water tds desired.

> I’m thinking a GAC cartridge is the way to go, since I don’t think I need to
> filter out particles less than 10 microns.  Is a carbon block a better idea?
> But would I need a pre-filter to keep the block from clogging too soon?

Probably. It would depend on how low the turbidity is in your tap water.

Sorry to sound negative. I think you have a good project that will provide
lots of processed water. Having been there, done that, I just wanted to share
my perceptions. I had 30+ years of facing the same problems for processing
water in my holography company. As you can see, I'm sold on the cost,
reliability and convenience of RO. [I've used both systems, a lot, BTW.]

There are several good suppliers of complete RO units to aquarists. They cost
a bit more (not much) than Home Depot, but provide ample expert support. The
one I know best is Dr. Ron Harlan, Back-To-Nature Aquatics in Glendale CA.
There is another in AZ that is highly regarded, but IDK the name. Ron
advertises in the big mags, but didn't have a web presence, the last time I

Good luck,


PS A point of aquatic philosophy: 

I don't mind the time and effort of doing water changes, feeding my fish,
trimming plants and vacuuming up mulm. I'm viewing and interacting with them
right when I do it, and it disciplines me to keep an eye on them before things
go bad. We both benefit.

Repetitive tasks that do not create that direct interaction need to be
minimized if we have any limits on our hobby time. Changing filters,
recharging ion-exchange chambers and responding to list questions fall into
that category, IMHO. ;-)

[Easy for me to say. I just moved and have no fish or plants, right now. WH]

- -- 
Wright Huntley 510 612-1467 - 879 Clara Drive, Palo Alto CA  94303

   "You need only reflect that one of the best ways to get
   yourself a reputation as a dangerous citizen these days is to
   go about repeating the very phrases which our founding
   fathers used in the struggle for independence."
           --   Charles A. Beard (1874-1948), U.S. historian

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