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CO2-safe Tubing

Contents:

  1. Silicone tubing and CO2
    by "David Bundy" <bundyd/semantique.com> (Sun, 19 Nov 2000)
  2. Aquatic Plants Digest V4 #667
    by Dave Gomberg <gomberg/wcf.com> (Sun, 19 Nov 2000)
  3. Silicone tubing and CO2
    by Paul Sears <psears/nrn1.NRCan.gc.ca> (Sun, 19 Nov 2000)
  4. Re:Silicone tubing and CO2
    by George Booth <booth/frii.com> (Sun, 19 Nov 2000)
  5. Aquatic Plants Digest V4 #668
    by EsTabu/aol.com (Sun, 19 Nov 2000)

Silicone tubing and CO2

by "David Bundy" <bundyd/semantique.com>
Date: Sun, 19 Nov 2000

On Sat, 18 Nov 2000 at 16:26:31 EST, Dave Grim <Dgrim62@cs.com> asked: 

> Can anyone give me information about using silicone tubing (100%) to deliver 
> CO2 to the tank? My main concern is wether or not the gas will make the 
> tubing brittle over time, or if there is a significant loss factor thru the 
> tubing (gas permeability)? Thanks for any help.


Jean-Paul Chicheret has written an article, dated Jan. 7, 2000, in which he
encourages us all to change our silicone tubing, which he says is far too 
permeable ("up to 30%"), for Tygon-brand tubing.  The article can be found 
at http://optimal.free.fr/jpc/articles/tygon_01.htm.  Since it's in French, I've 
hacked out a rough translation below:   


===============================

"The best way to deliver CO2

"Between the regulator, which is attached to a bottle of carbon dioxide, and the 
reactor or membrane diffuser, manufacturers of aquarium equipment generally 
supply us with silicone tubing.  However, this kind of tubing is highly permeable 
to CO2.  This becomes increasingly worrying as the tubing gets longer.

"What happens?

"Part of the CO2 which is passing through the silicone tube crosses the wall of 
the tubing, and enters the air.  Tests have recently shown that this can cause the 
loss of up to 30% of the precious gas.  I and a partner in the pharmaceuticals 
industry have run tests on no fewer than 10 kinds of tubing.  As you might have 
guessed, silicone tubing turned out to be the most permeable of all, that is, the 
tubing which allowed the most gas to escape.

"A solution to the problem?

"Yes, there is a solution!  The American company Cole-Parmer manufactures and 
distributes tubing made of TYGON®, which does not allow CO2 to get through.  
It is affordable, unlike the silicone tubing typically found in pet stores.  Its 
reference number is R-3603.  Being flexible, it is well-adapted to our 
installations.  TYGON tubing exists in many interior and exterior diameters.  It is 
not necessary to buy the thickest tubing available, but a thickness of 0.8 mm is a 
reasonable minimum.  Obviously, the thicker the tubing, the more resistant it will 
be as time passes.

"I would encourage all users of CO2 systems to change their silicone tubing for  
TYGON® tubing from Cole-Parmer.  This will result in substantial savings of 
this precious gas, as well as a better functioning system.  It's nonsense to mix in 
air with the CO2 and water in the reactor.

"I have now observed much better dissolution of CO2 in my Dupla S reactor.  
Air had regularly been mixing in with the CO2, causing some useless free space 
to be left over in the upper part of the reactor.  Since I have been using the 
TYGON tubing, the CO2 is practically all dissolved.  I have observed that the 
efficiency of the reactor, which is already quite impressive, is now even 
greater."

================================

Please note:  I'm playing journalist and translator here.  I don't know anything 
about tubing (silicone or Tygon or otherwise), nor do I know anything about 
Chicheret.  I've tried to keep my translation fairly close to the original, 
even when the French sounded odd (e.g. the reference to "precious" CO2).

David (B.)
Paris


Aquatic Plants Digest V4 #667

by Dave Gomberg <gomberg/wcf.com>
Date: Sun, 19 Nov 2000

At 03:48 AM 11/19/00 -0500, DGrim asked:
>Can anyone give me information about using silicone tubing (100%) to deliver
>CO2 to the tank? My main concern is wether or not the gas will make the
>tubing brittle over time, or if there is a significant loss factor thru the
>tubing (gas permeability)?

I have used Hagen Silicone tubing for several years and sold hundreds of 
CO2 systems using it.  I have not experienced, nor have my customers 
reported, any incidents of these problems.




- --
Dave Gomberg, San Francisco            mailto:gomberg@wcf.com
NEW Planted Aquaria Magazine:        http://www.wcf.com/pam
- -----------------------------------------------------------------


Silicone tubing and CO2

by Paul Sears <psears/nrn1.NRCan.gc.ca>
Date: Sun, 19 Nov 2000

> From: Dgrim62@cs.com
> Subject: Silicone tubing and CO2
> 
> Hey everyone,
> Can anyone give me information about using silicone tubing (100%) to deliver 
> CO2 to the tank? My main concern is wether or not the gas will make the 
> tubing brittle over time, or if there is a significant loss factor thru the 
> tubing (gas permeability)? Thanks for any help.

	I've never had a problem with Tygon tubing, which is a silicone.
It does have "relatively high gas permeability" (manufacturer's web page),
and is not suitable for use with acids (from a chemical point of view I
can see why), but any loss is pretty small, and the tube is just fine
after getting on for five years.

	The quoted permeability for CO2 is such that if the tube wall is
1 mm thick, and the pressure across it is 1 cm of mercury, then you will
lose about 2.5 x 10^-6 millilitres per second through each square centimetre
of tube wall.  The partial pressure difference across mine is about 76 cm
of mercury, so I may be losing a few mL per hour.  I suppose that is 
significant - I could shorten the tube.  It's the partial pressure of CO2,
not the overall pressure difference that matters - nitrogen and oxygen
are diffusing _in_ as well.

- -- 
Paul Sears        Ottawa, Canada


Re:Silicone tubing and CO2

by George Booth <booth/frii.com>
Date: Sun, 19 Nov 2000

>Date: Sun, 19 Nov 2000 05:54:32 -0500
>From: "Wayne Jones" <waj@mnsi.net>
>
>Jean-Paul Chicheret has written an article, dated Jan. 7, 2000, in which he
>encourages us all to change our silicone tubing, which he says is far too
>permeable ("up to 30%"), for Tygon-brand tubing
>
>I reply:
>
>I have heard this repeated before but I don't buy it at all. Silicone tubing
>does harden a little bit over time but it lasts many years. I have tested
>the tubing by placing my yeast sugar system under water and clamping off the
>end of the silicone tubing line. There were no detectable leaks at all let
>alone a loss of 30% of the gas. In my test situation the silicone line was
>under considerable pressure too. In actual practice the pressure in the CO2
>line is vanishingly small or even negative. Perhaps silicone tubing leaks if
>it is under 40 psi pressure but it sure doesn't seem to at low presssures.

Being permeable and leaking are two different things. If CO2 was diffusing 
through the silicone tubing in your test setup, it would dissolve directly 
into the water - you won't see any bubbles. Also, I don't see how you could 
measure a loss of CO2 - 30% or otherwise.


George Booth in Ft. Collins, Colorado (booth@frii.com)
"The web site for Aquatic Gardeners by Aquatic Gardeners"
   http://www.frii.com/~booth/AquaticConcepts/


Aquatic Plants Digest V4 #668

by EsTabu/aol.com
Date: Sun, 19 Nov 2000

In a message dated 11/19/2000 3:56:03 PM Eastern Standard Time, 
Aquatic-Plants-Owner@actwin.com writes:

<< "Yes, there is a solution!  The American company Cole-Parmer manufactures 
and 
 distributes tubing made of TYGON®, which does not allow CO2 to get through.  
 It is affordable, unlike the silicone tubing typically found in pet stores.  
Its 
 reference number is R-3603.  >>

it's between $62 and $103 for 50 ft. on their website, if you call that 
affordable...


- -Andrew 


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