# CO2 Tubing



## StaffyBull (Feb 3, 2007)

Whats the best tubing to use with CO2?


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## eklikewhoa (Jul 24, 2006)

I use the stuff clippard offers, I get mine from either John N. or RexGriggs


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## StaffyBull (Feb 3, 2007)

eklikewhoa said:


> I use the stuff clippard offers, I get mine from either John N. or RexGriggs


And that would be?


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## nailalc (Mar 17, 2006)

I also use clippard polyurethane tubing. Have also bought my tubing from Rex and John, links are below if you're ready to buy. Polyurethane offers the flexibility and strength that people want, while also minimizing the permeability of CO2 through the tubing. There is very little CO2 loss when compared to other materials.

http://www.rexgrigg.com/sale.html

http://www.aquaticplantcentral.com/...6-co2-supplies-manifold-co2-tubing-check.html

or you can find it on www.clippard.com


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## trenac (Jul 16, 2004)

I use the soft blue tubing that you can get form a LFS/LPS.


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## eklikewhoa (Jul 24, 2006)

polyurethane


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## epicfish (Sep 11, 2006)

trenac said:


> I use the soft blue tubing that you can get form a LFS/LPS.


Soft and blue? Kinda rubbery? Isn't that silicone?


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## Rex Grigg (Jan 22, 2004)

More than likely. And the tubing most likely to lose the largest amount of CO2.


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## furballi (Feb 2, 2007)

epicfish said:


> Soft and blue? Kinda rubbery? Isn't that silicone?


Silicone is perfectly fine for aquarium use (up to about 25 psig). Silicone is inert with CO2 and ozone, has good pressure retention characteristics, and is flexible. Why spend extra $ for "special" CO2 tubing when the basic silicon tubing will last for 5 to 7 years? To dispell the silicone "leak" myth, pressurize the silicone tubing up to 30 psig and dip the silicone tubing in a jar of water. Wait several days. Do you see tiny bubbles on the outside of the tubing?


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## epicfish (Sep 11, 2006)

furballi said:


> Silicone is perfectly fine for aquarium use (up to about 25 psig). Silicone is inert with CO2 and ozone, has good pressure retention characteristics, and is flexible. Why spend extra $ for "special" CO2 tubing when the basic silicon tubing will last for 5 to 7 years? To dispell the silicone "leak" myth, pressurize the silicone tubing up to 30 psig and dip the silicone tubing in a jar of water. Wait several days. Do you see tiny bubbles on the outside of the tubing?


Yes, it's fine for traditional aquarium use, yes it's flexible and inert with CO2 and silicone. It's inert with CO2...but it's porous by nature.

The pores within the silicone structure are miniscule, much smaller than the eye can see. That's why you don't see tiny bubbles on the outside of the tubing. It's been tested and there's ~6% leakage of CO2 per foot of silicone tubing.


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## furballi (Feb 2, 2007)

The leak rate is a funtion of tubing thickness and working pressure. 6% loss at 20 psig with 1/4" tubing is very high based on my experience in the aerospace industry. The major sources of air leaks are at the interconnects, not the tubing. Pay attention to metal-to-metal threads and seals.


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## Rex Grigg (Jan 22, 2004)

Here is a link to the math.

The Planted Tank Forum - View Single Post - CO2 Tubing

It's the most porous tubing you can get actually. I have a link to the chart if you want to see it.

The real test would be to place a coil of silicone tubing in a jar with water and pressurize it to 20 psi. Let it set for a couple of hours and test the CO2 levels.


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## trenac (Jul 16, 2004)

epicfish said:


> Soft and blue? Kinda rubbery? Isn't that silicone?


Yes it is. I've been using it for years with no loss of C02, from what I can tell. I mean, I'm getting a year supply of C02 off one tank fill-up. The blue tubing does not become stiff, it stays soft.


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## Rex Grigg (Jan 22, 2004)

I used to use silicone tubing on my main CO2 system. It feeds two tanks. I was getting about 8-10 months on a fill. I had a total of about 15 feet of tubing on this system. 

I switched out to the polyurethane tubing and got 17 months on the next fill and working on 14+ months on the current fill.


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## StaffyBull (Feb 3, 2007)

Rex Grigg said:


> I used to use silicone tubing on my main CO2 system. It feeds two tanks. I was getting about 8-10 months on a fill. I had a total of about 15 feet of tubing on this system.
> 
> I switched out to the polyurethane tubing and got 17 months on the next fill and working on 14+ months on the current fill.


Thats cool.

What size CO2 tank are you using?


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## Rex Grigg (Jan 22, 2004)

That system has a 20 lb cylinder and runs a 29 and a 55 gallon tank both with Bio-Wheels on them. So they go though a bit of CO2.


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## furballi (Feb 2, 2007)

Rex Grigg said:


> Here is a link to the math.
> 
> The Planted Tank Forum - View Single Post - CO2 Tubing
> 
> ...


There are several issues with that calculation...

1. 3/16" ID tubing is quite large. I use 1/16" to 1/8" max. We're trickling CO2 into the water column so there is no need for large tubing.

2. The thickness assumption is 1/32". The nominal thickness of quality silicone tubing is 1/16" to 1/8".

With these new variables in place, the real-world loss as compared to polypropylene is less than 2.5%. With 5' silicone length, the leak rate is insignificant when one accounts for the potential leaks at all the junctions.

Instead of focusing on the trivial loss of CO2 via silicone tubing, one should be more concerned about CO2 bubbles going to the surface of the tank! That's almost 100% loss.

I use an Aquaclear 300 filter to diffuse CO2 into the water. There is no visible bubble at the outlet. A 5 lb tank is good for 1.7 year (50 gal aquarium).


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## Left C (Jun 14, 2005)

I use this black CO2 tubing from Marine Depot. I run it from the regulator to the brass check valve. It also comes in a blue and a green color. CO2-Proof Tubing - Black - Marine Depot - Marine and Reef Aquarium Super Store

From my brass check valve to the reactor/diffuser I use the Tygon Lab R-3603 tubing. It's stays soft and flexable. Tygon® Laboratory Tubing R-3603 - US Plastic Corporation


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## AaronT (Apr 26, 2004)

Here's the link to directly to Clippard. If you want to buy in bulk it's cheaper this way. http://www.clippard.com/store/byo_tubing/?sku=URH1-0804-CLT-050

That's a link for clear tubing, but they have other colors if you want something different.
Also, it doesn't hurt to do a search on their website for a dealer near your home.


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## Rex Grigg (Jan 22, 2004)

furballi said:


> There are several issues with that calculation...
> 
> 1. 3/16" ID tubing is quite large. I use 1/16" to 1/8" max. We're trickling CO2 into the water column so there is no need for large tubing.
> 
> ...


Actually the wall thickness of standard aquarium silicone tubing is 1/16th of an inch. OD is 1/4" and ID is 1/8". So the wall thickness is 1/16". 3/16th" tubing is actually smaller than the standard silicone tubing as it is as I stated 1/4" or 4/16" in OD.

So the numbers are quite correct.


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## Rex Grigg (Jan 22, 2004)

AaronT said:


> Here's the link to directly to Clippard. If you want to buy in bulk it's cheaper this way. http://www.clippard.com/store/byo_tubing/?sku=URH1-0804-CLT-050
> 
> That's a link for clear tubing, but they have other colors if you want something different.
> Also, it doesn't hurt to do a search on their website for a dealer near your home.


You have to buy a bunch as their shipping is more and they have that pesky $10 handling fee. And I do discount for large orders of tubing.


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## furballi (Feb 2, 2007)

Rex Grigg said:


> Actually the wall thickness of standard aquarium silicone tubing is 1/16th of an inch. OD is 1/4" and ID is 1/8". So the wall thickness is 1/16". 3/16th" tubing is actually smaller than the standard silicone tubing as it is as I stated 1/4" or 4/16" in OD.
> 
> So the numbers are quite correct.


One of the best high quality needle valve is the Fabco NV-55 with 10-32 thread at the outlet port (about $15). Quality silicone tubing with small ID can be purchased from McMaster Carr for about $0.75 per foot. Smaller tubing translates to a smaller bubble and finer flow control.

http://www.mcmaster.com/


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## SpaceBug (Jan 10, 2007)

I may be going off the deep end here, but does anyone use metal tubing for their CO2 gas? I have an external CO2 reactor so it would be easy enough to run copper tubing from my regulator to the reactor.


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## Rex Grigg (Jan 22, 2004)

furballi,

I have tried the Fabco NV-55. And I have tried the Clippard MNV-4. The Clippard beats the Fabco hands down. In fact if you look at the published flow rate chart for both parts it's clearly apparent that the Clippard is the better part. And again, silicone leaks like a sieve. See the chart at this link. I know that math is not your strong point from one of your previous posts on this thread. I have attempted to correct the numerous mistakes you made on tubing size and wall thickness. Even if you get silicone with a slightly thicker wall thickness, say 3/32" over 1/16" (thats' the same as 2/32") it's not going to make a lot of difference. But you seem not to have read that at all. Perhaps it's because you don't want to admit you are wrong. But you are. Silicone sucks. Stop. Period. End of story.

Bigger numbers are worse. Silicone has the LARGEST permeability numbers of any tubing listed on that chart. If that is not enough to get you to realize that silicone is a bad choice then nothing is. Silicone is used as airline tubing because no one cares if it diffuses air though the tubing because air is free. And silicone is cheap and easy to work with. It's not because it's a better choice.

Spacebug,

Metal tubing is pretty much overkill.


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## furballi (Feb 2, 2007)

Rex Grigg said:


> furballi,
> 
> I have tried the Fabco NV-55. And I have tried the Clippard MNV-4. The Clippard beats the Fabco hands down. In fact if you look at the published flow rate chart for both parts it's clearly apparent that the Clippard is the better part. And again, silicone leaks like a sieve. See the chart at this link. I know that math is not your strong point from one of your previous posts on this thread. I have attempted to correct the numerous mistakes you made on tubing size and wall thickness. Even if you get silicone with a slightly thicker wall thickness, say 3/32" over 1/16" (thats' the same as 2/32") it's not going to make a lot of difference. But you seem not to have read that at all. Perhaps it's because you don't want to admit you are wrong. But you are. Silicone sucks. Stop. Period. End of story.
> 
> ...


Hehehehhh...when you've completed differential equations with multiple variables, then we will re-visit math.

The leak rate of silicone is expressed in {cc-mmsec-cm2-cm Hg } x 10-10! Note the 10-10 power. You are obsessed with a tiny number that don't mean squat in the real world. I along with many others have used silicone tubing without encountering abnormal CO2 loss. The biggest loss of CO2 occurs when the CO2 bubbles evaporate out of the tank. Control this variable and you will see a dramatic drop in CO2 usage!

I cannot comment on the Clippard product, because I have no hands-on experience. However, let's look at their specs.

NV-55: 4 turns...0.83 SCFM @ 80 psi
MNV-4: 4 turns...0.95 SCFM @ 100 psi

Based on published data, the Clippard is quite linear up to about 4 turns. The Fabco product is linear up to 9 turns and is rated for bubble-tight shut-off.

Perhaps you can clarify to others why you make the claim that "if you look at the *published flow rate chart for both parts* it's clearly apparent that the Clippard is the better part". I have included links containing flow rate vs. # of turns for both products. Don't discount the NV-55 just because it doesn't appear on your part list.

In summary, it's a tie for flow rate between the two products, up to 4 turns. The Fabco is a better product above the 4th turn because its flow rate is linear throughout its 9-turn working range. I've purchased the NV-55 for less than $10 locally. Call around for best price.

Note that most of the fine metering occurs during the first turn. I have no problem generating a 1-1.5mm diameter CO2 bubble every 30 seconds (+/-2 seconds) with the Fabco NV-55 valve using 10 psig inlet pressure and 2" water column. Check out the Ideal needle valve below for greater precision in metering.

http://www.fabco-air.com/pdf/Sec_12.pdf

http://www.clippard.com/downloads/g...by Section/Flow Control and Needle Valves.pdf

If $ is not an issue or if you desire greater precision in metering, then go with the Ideal -1- valve with 0.0190 Cv ($68 at McMasterCarr page 417). Parker also has a very high-performance needle valve, but you'll have to spend big bucks for that toy.

http://www.idealvalve.com/brassvalves.htm

http://www.mcmaster.com/


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## Rex Grigg (Jan 22, 2004)

Since we are actually operating these needle valves in the first turn or two and not even close to 4 turns or 9 turns open the little differences are huge. I have used and own both valves. The Clippard is the better valve. I would prefer to use the Swagelok SS series but at $50 for brass and $100 for Stainless Steel it's a bit much. 

I sell the Clippard because I and many other people have had better luck with it at the flow rates we use.

I can get either valve at the same place. So it's experience here. And it's experience with the tubing as well.

A simple test. Take a length of silicone tubing and submerge it in water. Close off the end and then pressurize it to 10 psi. Wait a couple of hours and measure the CO2 level in the water. Or even just pressurize the tubing and then close the valve. Wait a while. Notice how the silicone tubing goes flat? That's because the gas inside has dissipated though the walls of the tubing.

I know someone that built a great auto water change and top off system on a aquarium. Using silicone tubing on the system it would drop about 1/8" of an inch each cycle due to the air dissipating through the silicone tubing. When he switched to the tubing I sell it was spot on every cycle.


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## furballi (Feb 2, 2007)

Rex Grigg said:


> Since we are actually operating these needle valves in the first turn or two and not even close to 4 turns or 9 turns open the little differences are huge. I have used and own both valves. The Clippard is the better valve. I would prefer to use the Swagelok SS series but at $50 for brass and $100 for Stainless Steel it's a bit much.
> 
> I sell the Clippard because I and many other people have had better luck with it at the flow rates we use.
> 
> ...


1. You claimed that the Clippard is a much better valve, yet the specs don't support your case. Anyone can brag that product A is better than product B. Why is the Clippard better than the Fabco when its published spec is worse than the Fabco? If I can achieve one 1.5mm diameter CO2 bubble per 30 second with the Fabco, then the resolution of this needle valve is more than adequate for 99.99% of those who are interested in increasing the CO2 level of their planted tanks. Also note that the Fabco uses a straight 3 degree taper needle to achieve the excellent linear control from turn 0 to turn 9.

The gold standard in metering valve is the Parker HR1 with 15 turn and Cv value of 0.007.

2. You continue to harp on the inferiority of silicone tubing while sidestepping the huge waste of CO2 gas bubbles as they escape into the atmosphere at the top of the tank. That's 100% loss CO2 in a few seconds! Eliminating this waste can easily triple the life of your CO2 supply.

Good experiences are supported by data and real-world use.


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## Rex Grigg (Jan 22, 2004)

Point #2. I use a DIY reactor and NONE of my CO2 bubbles to the surface to escape. I've never been a fan of any method of CO2 diffusion that allows CO2 bubbles to reach the surface. If you are using such a method then you should expect high CO2 use.

There is a difference between a metering valve and a needle valve. I have used both the Fabco and the Clippard. The Clippard is the better valve. You stated you have NOT used the Clippard. You might want to get one and try it out.


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## tfmcder (Feb 22, 2006)

You guys are entertaining!!! I'm enjoying this argument/discussion. Just keep it clean boys and neither take anything personal. You both are presenting great arguments. Just keep it in good taste and remember we all want the same things here...beautiful tanks that are easy to maintain.


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## furballi (Feb 2, 2007)

tfmcder said:


> You guys are entertaining!!! I'm enjoying this argument/discussion. Just keep it clean boys and neither take anything personal. You both are presenting great arguments. Just keep it in good taste and remember we all want the same things here...beautiful tanks that are easy to maintain.


I deal with facts, not pie-in-the-sky statement like product A is better than product B. Why should anyone try the Clippard when its published spec is clearly inferior to the Fabco? An experienced designer should be able to identify the better valve when armed with the appropriate technical literature.

The term metering valve is used to describe a precise flow control device with low to very low Cv (flow coefficient). Its Cv vs. Number of Turns graph is often linear from close to full open. The Cv vs. Number of Turns graph of a less precise flow control device tends to mimic a parabolic curve. This is because the orifice and needle valve are designed to accomodate a higher flow rate.

If all else are equal, a valve with a linear Cv vs Number of Turns graph will always be the preferred choice unless it is too restrictive to deliver the desired mass flow rate. It's also important not to overspec a valve, since one with lower Cv and linear response with cost a lot more $.

Note the Cv vs. Number of Turns graph near the bottom of this page. The more accurate yellow graph depics a very precise metering valve with 0.031 orifice.

http://www.idealvalve.com/flowcal.htm

I have no doubt that both the Clippard and Fabco products will do the job for anyone interested in CO2 injection for submersible plants. However, I have to be suspicious about anyone claiming that the Clippard is a better engineered product. The published spec clearly do not support this claim.


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## SpaceBug (Jan 10, 2007)

Oh, I can't believe I'm going to say this, but ....

There are published specs and then there is actual experience. If experience contradicts the specs, which are you going to believe?


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## Salt (Apr 5, 2005)

According to Cole Parmer's permeability chart, FEP (fluorinated ethylene propylene) has the best spec for CO2. My understanding is it's a plastic with a crystalline structure similar to glass.


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## StaffyBull (Feb 3, 2007)

op2:


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## Left C (Jun 14, 2005)

USPlastic.com sells Tygon® Chemfluor® FEP Tubing: Tygon® Chemfluor® FEP Tubing - US Plastic Corporation

Tygon® Chemfluor® FEP Tubing 
Excellent physical and electrical properties. Wide range of working temp. -100°F to 400°F. Fluorinated ethylene propylene (FEP) is a chemically inert thermoplastic.Transparent tubing is excellent for acids (all concentrations), aliphatic alcohols, aldehydes, bases, esters, hydrocarbons (aliphatic, aromatic and halogenated), ketones and strong oxidizing agents. Can be rigorously cleaned in boiling nitric acid for high-purity analysis. Tubing formulation meets FDA standards CFR 21 for food packaging, per paragraph 177.1550. Do not radiation-sterilize. Sold in 25' intervals only. Sold in 25' intervals only.


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## AaronT (Apr 26, 2004)

Vinyl tubing is also available from your local hardware store. According to the Cole Parmer chart linked above by Salt it lets out even less CO2 than polyurethane.


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