How much CO2 leaking is acceptable?

[Eigenbrau]

I know that seems like a stupid question and your first response is probably, "None, jackass!", but hear me out for a sec. I have a kegerator that holds two cornys. Attached is a 20lbs. cylinder and a dual regulator. I had a leaking issue that turned out to be a combination of the relief valve and gas post on one of the kegs. The other keg tested fine.

My issue is, I opened the tank up and pressurized my good keg to 10 psi. I then shut off the tank and left the pressure in the line. On the regulator, I have a gauge that shows the cylinder pressure which is typically 800 psi. So, after shutting the tank off, the cylinder gauge read 800, the regulator is at 10, and the tank is pressurized with all valves leading to opened. 24 hours later, the cylinder gauge shows 500 psi, indicative of a slow leak, correct? Is this acceptable? I've run through everything imaginable with star-San solution to look for leaks and have found nothing. There is no liquid in the keg for the gas to diffuse into. Any possible suggestions or physics quirks I'm missing?

 

[lumpher]

teflon tape all your connections. that'll stop the leak. a 20 lb tank should last most people a year or 2

 

[Ohio-Ed]

The high pressure gauge is next to useless.
It will fluctuate with temp changes which is likely what you are seeing.

CO2 is liquid. The "head space" in the tank is pressurized co2 gas and will remain pretty constant (but fluctuate with temp changes) as long as there is ANY liquid remaining in the tank. When the liquid is gone, the pressure (and gauge) will drop like a rock.

Don't think of the high pressure gauge as a Gas Gauge like on your car... it's more like "Yes / No" to the question is there gas in the tank.

The only real way to know how much co2 is left in the tank is to weigh it.

Ed

 

[Ohio-Ed]

teflon tape all your connections. that'll stop the leak. a 20 lb tank should last most people a year or 2

Don't use teflon on flare connectors. They are made to seal by seating, not at the threads.

The teflon can prevent the connections from seating properly.

Ed

 

[lumpher]

Don't use teflon on flare connectors. They are made to seal by seating, not at the threads.

The teflon can prevent the connections from seating properly.

Ed

true, ed. good thing to point out

 

[brewingkitty]

i put at least 5 wraps of teflon on ALL my male threads... including the flare fittings, just make sure to keep it off of the 45* flare bevel. i can set each regulator to 30psi, back the adjustment screws out and shut off the tank and 3 days later have the SAME pressure reading on the high pressure gauge. ie. no loss.

 

[bad coffee]

I've never had any luck using starsan to find leaks.

Try a bunch of dish soap with a little bit of water. Just enough to make the soap completely liquid.

B

 

[doubleb]

Hi I just kegged for the first time. My tank just capoots(it was used so I'm not sure how much there was to begin with). Is the a safety issue for me, my kids, or my cat if there is a leak and a lot had gotten out? Also, what about the beer. Is it going to be OK if it (worse case senario) lost all its co2?

 

[Special Hops]

Hi I just kegged for the first time. My tank just capoots(it was used so I'm not sure how much there was to begin with). Is the a safety issue for me, my kids, or my cat if there is a leak and a lot had gotten out? Also, what about the beer. Is it going to be OK if it (worse case senario) lost all its co2?

It is not a safety issue like Carbon Monoxide in that CO2 is not a poisonous gas. If your setup is in a small enclosed room it could be that the leaking CO2 replaces the oxygen in the room which could lead to obvious problems. But in a reasonably well ventilated area don't worry about it.

Beer will be fine. probably flat, but fine. Just recarb it and you are good to go.

 

[Ohio-Ed]

i put at least 5 wraps of teflon on ALL my male threads... including the flare fittings, just make sure to keep it off of the 45* flare bevel. i can set each regulator to 30psi, back the adjustment screws out and shut off the tank and 3 days later have the SAME pressure reading on the high pressure gauge. ie. no loss.

That means your temperature didn't change (or at least change much).

I've seen a lot of threads where folks think they have a co2 leak and it turns out they just don't realize how the gauge works.

Ed

 

[Eigenbrau]

The high pressure gauge is next to useless.
It will fluctuate with temp changes which is likely what you are seeing.

CO2 is liquid. The "head space" in the tank is pressurized co2 gas and will remain pretty constant (but fluctuate with temp changes) as long as there is ANY liquid remaining in the tank. When the liquid is gone, the pressure (and gauge) will drop like a rock.

Don't think of the high pressure gauge as a Gas Gauge like on your car... it's more like "Yes / No" to the question is there gas in the tank.

The only real way to know how much co2 is left in the tank is to weigh it.

Ed

I understand the concept behind the gauge, but keep in mind the tank was closed off. I lost no pressure in the keg line, but the fact the high pressure gauge was dropping led me to believe there was a leak. Should I watch the keg line pressure fir a few days and see if it drops? I had some water back up into the regulator (no check valves yet) and thought that maybe this was the issue. I disassembled the regulator, dried it, and put it back together.

 

[Eigenbrau]

Pardon my spelling/grammar, I'm on my phone.

 

[SweetSounds]

The answer really is "0"

For the MFL fittings, go to the LHBS and get some nylon flare washers. Mine sells them for a dime. These must be used on metal-to-metal junctions like from a MFL swivel nut on a hose to a MFL valve on a manifold.
The plastic-to-metal junctions should be self sealing (Like a QD to a swivel nut) Make sure there isn't any molding flash on the face of the MFL on the QD and it should seal up great.
Your regulator must have a nylon washer between the reg and the tank valve. They are cheap too, and it's good to have a few extra laying around.
Kegs are sealed inside and outside of the posts by O-rings. These should be in good shape, and can be ordered from McMaster for about $2.00 for 100.

None of these fittings will benefit from Teflon tape, as they are all designed to seal by compression of mating faces. One thing that can help here is keg lube.

Teflon tape is designed to seal tapered pipe threads. So it will be useful for any NPT connections - Valves into manifolds, Low pressure fittings on regulators, and other things like that.

6 things to always keep in the toolbox:
Corny lid O-rings - $12 for 10
Corny post O-rings - $2 for 100
Corny dip tube O-rings - $2 for 100
1/4" MFL washers - $0.10 each
High pressure tank washers - $0.10 each
And Keg Lube!

For $20 you can make sure you never have a leak due to a fitting in your system...

 

[strat_thru_marshall]

I understand the concept behind the gauge, but keep in mind the tank was closed off. I lost no pressure in the keg line, but the fact the high pressure gauge was dropping led me to believe there was a leak. Should I watch the keg line pressure fir a few days and see if it drops? I had some water back up into the regulator (no check valves yet) and thought that maybe this was the issue. I disassembled the regulator, dried it, and put it back together.

If you had the gas line turned off and you didnt lose any keg pressure, I would say you don't have a leak.

Like Ohio-Ed said, that gauge is basically a "full or empty" gauge. If it's above 100psi, the tank has gas in it. The volume of compressed liquid co2 in the tank could stay exactly the same, and the gauge will go up and down depending on temperature. Mine reads 800 PSI when I bring it home from being filled, and after a night in the keezer it reads 500 PSI where it remains until it drops to 0 almost instantly when it runs out.

If soaping all your fittings and connection points doesnt reveal a leak....you probably dont have a leak.

 

[Ohio-Ed]

I understand the concept behind the gauge, but keep in mind the tank was closed off. I lost no pressure in the keg line, but the fact the high pressure gauge was dropping led me to believe there was a leak. Should I watch the keg line pressure fir a few days and see if it drops? I had some water back up into the regulator (no check valves yet) and thought that maybe this was the issue. I disassembled the regulator, dried it, and put it back together.

You didn't say it the temp of the tank changed?

All the advice from others in this thread is sound.

I would add that if you have checked out all the things suggested, the regulator "re-build" you did may be the culprit.

Ed

 

[Eigenbrau]

No change to tank temp. The house varies between 75 and 80 degrees, so it would have been very minimal.

I thought the same thing after the regulator rebuild. I wasn't sure if the gasket inside was supposed to be changed after disassembly, but I've done this in the past with no issues. There is a possibility I screwed something up or the gasket didn't seat right. I'll have a look at it when I get home. Thanks for all the help/advice.

 

[brewingkitty]

check valves NEED to be #1 on your next parts shopping list to prevent tons of potential problems.

 

[rodd]

Just a note, if your beer isn't completely done carbing, the CO2 could be going into solution. (assuming the keg isn't empty) I don't think your experiment necessarily means you have a leak.

 

[Ohio-Ed]

Just a note, if your beer isn't completely done carbing, the CO2 could be going into solution. (assuming the keg isn't empty) I don't think your experiment necessarily means you have a leak.

If you read the OP, the keg being tested is empty.

 

[rodd]

sorry, I missed that.

 

[malkore]

500psi is the normal pressure for a cold CO2 tank (cold as in beer fridge temperature).
at room temperature, its 900psi.

You have no leak, you have liquid to gas physics at play.