# co2 leak? need help



## grobered (Feb 9, 2005)

I have pressurized co2, the other day I noticed the co2 tank was empty, much earlier than I expected it to be. I thought there might be a leak so I replaced all of the tubing, had the co2 tank refilled and reconnected everything. Two days later the co2 tank is almost empty again. I checked all connections with gas leak spray (soapy water) and didn't find anything. I had recently moved my aquarium so now an air conditioning vent is blowing directly on the co2 tank. Could the cold temperature make the tank put out more gas than I am able to regulate? My needle valve seems to be okay as does my regulator. Any ideas or comments? Thanks

grovbered


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## Rex Grigg (Jan 22, 2004)

Did you use a new washer when you put the regulator on the cylinder?

Did you tighten the regulator nut with a wrench?

The cold air is NOT the problem. You have a leak. You need to find the leak. Make sure all connections are tight. And if you are emptying a cylinder in a couple of days it's not the tubing, assuming the tubing has no large gaping holes anyway.


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## reizao (Feb 8, 2007)

Silicon tubbing leaks about 30% of the co2 it deliver.


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## Minsc (May 7, 2006)

Make sure the tank is actually getting filled properly. It should be ice cold and significantly heavier than when you bring it in. Some people have no idea what they are doing...

Often you can hear leaks if you get your ear close enough. If you are actually going through a tank that quick, there should be some serious hissing!


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## taekwondodo (Dec 14, 2005)

reizao said:


> Silicon tubbing leaks about 30% of the co2 it deliver.


Urban myth.

To find a leak - add several drops of dishsoap to a cup of water. Liberally pour the water (have towels handy) over the connections (regulator-Tank, regulator-needle valve, etc...).

If you see bubbles, there is your leak.

You won't see any bubbles if you run the soap solution over the silicone tubing...and if you do, you have bad tubing.

Oh - and don't drop the soap... (into the tank).

- Jeff


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## hoppycalif (Apr 7, 2005)

One leak source I have found is at the sealing washer between the regulator and the CO2 bottle. If you tighten that connection with the bottle still very cold right after being refilled, the connection will loosen as things warm up. So, I found I have to retighten it every hour or two for a day, then recheck it for tightness a couple of times the next day. I'm not sure why the loosening occurs, just that it does, and it isn't just a slight loosening either.

Another slower leak source, with a Milwaukee regulator, is at the bottom of the bubble counter. I found I couldn't stop that leak no matter what I tried, so I ended up just removing the bubble counter. That one I found because there was always dampness under the bubble counter - the leak pushes water out along with the CO2. It is just a slight leak, so it probably isn't what you have.

The secret to leak checking is to liberally coat everything that could possibly leak with soap solution, then waiting several minutes and looking for little mounds of bubbles. Those are the leaks, and they don't show up instantly.


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## Rex Grigg (Jan 22, 2004)

Silicone tubing leaks a lot of CO2. It's not an urban myth. It leaks around 6% per foot. And I have a link to the math that shows the proof.

One can actually make a CO2 diffuser out of silicone tubing. Just coil 10-20 foot of it up and plug the end. Then run the CO2 into it.


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## grobered (Feb 9, 2005)

Thank you all for your suggestions.

I have had the same set up for over two years, the only difference is the location of the aquarium. The co2 supplier is the same so I think they know how to fill a tank. I never connect the regulator until the co2 tank has been sitting in the house for a couple of hours. I use a wrench and a new washer everytime I connect. I applied soapy water to every connection there is, at the solenoid, the check valves, the diffuser, the needle valves, etc. I do use blue silicon tubing but it is new so there shouldn't be any large holes even if there is micro leakage. (What is a better type of tubing?) 

I am baffeled, I even asked the guy at the co2 supplier about regulator failure, he said it happens but not in a relatively new system with tight connections. I checked all the fittings on the regulator and they are tight.

grobered


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## Rex Grigg (Jan 22, 2004)

Any tubing is better than silicone.

I use and provide polyurethane with all my regulators.

To empty a cylinder in two days you have to have a leak somewhere. And a good sized leak. Did you check the regulator for leaks? 

And which regulator are you using?


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## taekwondodo (Dec 14, 2005)

Rex Grigg said:


> It leaks around 6% per foot. And I have a link to the math that shows the proof. One can actually make a CO2 diffuser out of silicone tubing. Just coil 10-20 foot of it up and plug the end. Then run the CO2 into it.


I would like to see the actual results of a real scientific test vs. some "math posted on a web-page". Way back (in the mid '90s), this was posted on APD (by some guy pushing his expensive tubing along with regulator systems) and the whole concept was never really challenged and became gosple. Most on APD continued using silicone as it was cheap and easily available.

95% of the CO2 systems we use have almost no differential pressure between the outside of the tubing and the inside of the tubing - making the only action to cause CO2 to traverse the silicone barrier would be osmotic pressure forcing the CO2 through the silicon. I would even be willing to bet on those systems injecting that the pressure inside the tubing is less than it is on the outside of the tubing because they feed into venturis (suction).

Losing any CO2 would have to assume a very high pressure difference between the inside of the tubing and the outside of the tubing... I've been using silicone off and on for 10+ years and have never noticed the difference - my 10lb tank lasts consistently 7-8 months regardless of tubing type. This should be a simple experiment to set up (Call Mythbusters on the Discovery channel).

Regardless, I think we can all agree that the tubing type has absolutely nothing to do with grobered's "leak".

If his fish aren't dead and floating at the top - it's somewhere at/around the regulator.


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## vic46 (Oct 20, 2006)

Does your bubble counter have a plastic barrel? If so, take it apart and inspect very carefully for cracks. I have had this problem. Also, you might try using Teflon tape in the metal to plastic unions to enhance the seal.
Vic


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## kiwik (Apr 3, 2007)

glad to hear silicone tubing doesn't leak too much co2 cuz i was just beginning to wonder if i had to replace it.


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## vic46 (Oct 20, 2006)

kiwik said:


> glad to hear silicone tubing doesn't leak too much co2 cuz i was just beginning to wonder if i had to replace it.


You might want to reread Rex Grigg post above. He indicates that silicone tubing leaks 6% per foot. 10 feet would be 60% lost!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!


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## Rex Grigg (Jan 22, 2004)

Here is the chart with the numbers. Note that silicone has the highest Permeability of all listed tubings.
http://www.coleparmer.com/techinfo/...E,C&htmlfile=SelectingTubing.htm&Title=Search

Here is the math.
http://www.plantedtank.net/forums/213172-post11.html

You can not dispute that silicone has the highest permeability of all commonly available tubings.

Now the real world experience. I feed a 55 gallon and a 29 gallon from one system. I had silicone tubing through the whole system. I was getting about 8-9 months off of a 20 lb cylinder. I replaced all the tubing with polyurethane tubing and got 17 months with the next fill. The current fill is at 12 months. Other people have reported the same results. Note that both tanks were running 24/7 and had remote needle valves so the working pressure though most of the tubing was round 12-15 psi.


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## taekwondodo (Dec 14, 2005)

Rex Grigg said:


> Here is the chart with the numbers. Note that silicone has the highest Permeability of all listed tubings.
> http://www.coleparmer.com/techinfo/...E,C&htmlfile=SelectingTubing.htm&Title=Search
> 
> Here is the math.
> ...


Your whole premise is based on the argument that "there is significant pressure (15 lbs or better) _difference_ between outside air, and the inside of the tubing" - and this pressure difference will cause you to lose 6% per-foot.

_Most_ CO2 systems do not have any significant pressure at all between the regulator/needle valve and the reactor. The permeability is a function of the back-pressure created between the reactor and the valve - no back-pressure, no permeability.

As this delta goes to zero:
2) deltaP = pCO2_inside - pCO2_outside

the whole "6%/foot theory" falls apart.

<edit - had to leave, just got back from training to finish my thought>

Atmospheric pressure in 12 inches of water is 0.4336 psi, representing a 2.2 cm-Hg difference between the outside and the inside of the tubing (vs the delta of 75.2cm-Hg at 15 lbs of pressure used in the example to get the 6% per foot).

I'm going to overly simplify things from here on out - 2.2 cm-Hg is _2.9%_ of 75.2cm-Hg.

Net loss of CO2 in a non-pressurized application where the bubbles from the CO2 were being pushed to 12" under the water, unrestricted from the regulator/needle-valve/bubble counter to the reactor would result in a _0.174%_ loss of CO2 per foot (yes, _the decimal is in the right place_).

Seems pretty innocuous to me. On my $20 refill for my 10lb tank, that's costing me $0.034 (three-point-four cents, or 1/2 ounce of CO2 out of a 10 lb bottle).

Like I said, I have noticed no measurable difference between the two. I see and understand your set-up for running it pressurized - I wouldn't have done it that way - would have too hard a time to keep the tubing from blowing off the regulator (been there, done that - pop-bottle bubble counters explode at this pressure).


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## taekwondodo (Dec 14, 2005)

grobered - any update?

Now that we've verified that losing 30% of the CO2/foot by using silicone tubing is indeed an urban legend  ...

Sometimes if I don't tighten the [email protected] out of the regulator when I'm putting it on the bottle (there's 800 PSI at that connection), I'll leak a bottle away in a week or so. Also, do you put a new washer in the regulator each time you get a refill?

Also, what/when do you get the first indication that the tank is almost empty?

- Jeff


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## grobered (Feb 9, 2005)

Here is an update.

I bought co2 proof tubing and a new needle valve from Marine Depot. I had the co2 tank refilled and set everthing back up. I checked all connections for leaks several times. Things were working well for four days. Last night I checked the bubble counter just before going to bed and eveytihing was looking good.

This morning the co2 tank is empty. I have the solenoid on a timer, I can't remember what the tank psi was but it was not zero. The regulator was around 8 lpm, so either the tank or the regulator is messed up. Agree? I use a U.S. GENERAL (ITEM 47259) REGULATOR. 

I am going to take the co2 tank and the regulator to my co2 supplier and see if they can check them out. Any othe ideas. The bubble counter is okay. When I blow on one end and cover the other with my finger there is no leak.

Thanks for all your concern and input.

grobered


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## hoppycalif (Apr 7, 2005)

You can't find leaks by blowing on something. You can only generate about 1 psi by blowing, but the CO2 pressure will be as much as 30 psi up to the needle valve and 2 psi downstream of it. You have to use soap solution to find the small leaks that will deplete your tank. Your CO2 leaked out totally in 4 days, which may seem fast, but is really a slow leak. While it was leaking and there was still liquid CO2 in the tank, the tank pressure didn't drop. But, once the liquid was used up, the remaining gas leaked out quickly.

I found that leak checking with soap solution had to be done by liberally soaking every single connection with the solution, then waiting for as much as 30 minutes for little mounds of bubbles to collect where the leaks were. It is a slow process, but an effective one.


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## grobered (Feb 9, 2005)

If anyone is still interested I finally found the leak. It was on the solenoid. It is a Clippard brand and I have had it for a while without problems until now. There is a small plate between the electrical component (black) and the switch where the gas runs through(silver). This is where the bubbles formed. The moral of the story is never overlook any part of your system. I never heard of this happening and neither did anyone else, but it did.


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