Checking for Draft System CO2 Leaks – Using The Pressure Gauge Method

check for co2 leaks

For the most part, checking for keg liquid and CO2 leaks is pretty straightforward.  Is beer leaking?  Then you’ve got a liquid leak.  Is there six inches of beer in your kegerator?  That one’s really easy to spot.  If beer is shooting out like a geyser, you’ve got a… fast leak. 🙂

For kegerator CO2 leaks, it’s a generally a little more work, but still pretty easy… spray everything with Star San solution (diluted of course) and look for bubbles.

A problem spot.  There is one place on the CO2 side that the soak-everything-with-Star-San method doesn’t really work…. the keg’s gas post.  Testing at this point using the spray bottle method is impossible (or at the very least difficult and messy).  Unless your poppet is messed up, leaks will only surface here when a gas QD is actually engaged.  The problem is, you can’t easily see that spot when a QD on.  Stated more simply, you need a QD on to see if it’s leaking, but you can’t see it if a QD is on.

Enter what I call the “pressure gauge method”.  The pressure gauge method can check the entire keg including gas QD connection and any connected tubing without soaking everything and the resulting clean up.

My process for that…

  • Charge your keg with CO2 as usual.  Use your usual serving pressure.  Over-pressurizing can mask leaks that may otherwise show themselves.
  • Remove the CO2 line and replace with a pressure gauge or Spunding Valve – with the adjustable PRV set to a very high pressure so that not gas escapes.
  • After the pressure has stabilized. I mark the current pressure with a wax pencil, or you can just remember what it reads
  • Wait for a couple hours to overnight to see if the gauge drops.
  • If it drops quickly, there is a leak someplace in the system.  Note: If your keg has beer in it that is uncarbonated the pressure will drop some overnight (it is equalizing and carbonating the beer).  What you don’t want is a quick drop in pressure.
  • This technique tests the entire keg including the gas post, o-ring, QD and any tubing that’s connected.
  • In my experience, over long periods of time there will be some slow gauge movement.  I don’t know if these are micro leaks or temperature related, but I’m not really concerned with that, I am looking for a relatively quick drop in pressure.  Something that shows up within a couple hours.

This technique also has the advantage of saving Star San and saving some clean up that’s required when you soak gear in Star San.

Related: Why Won’t My Homebrew Carbonate? Fixing Beer Carbonation Problems

If the CO2 gauge method indicates a leak, you can start spraying with Star San to hunt it down.  If you cannot find the leak, I would suggest changing your gas post o-ring to see if that’s the culprit.  I’m quick to replace o-rings, especially on the gas side.  I have lost a couple full tanks of CO2 to a bad gas post o-ring.  These typically cost just pennies [See: Bulk Keg Orings and Keg Repair Part Numbers].  I would much rather be safe that sorry when it comes to the time, cost and inconvenience of replacing an empty CO2 tank.  After you change the gas o-ring, re-check using the pressure gauge method.

This is one of the many uses of a Spunding Valve – See: Build a Spunding Valve

I’m not suggesting this as a replacement for the Star San spray method.  Practically speaking, I use it as a complement to that to test an otherwise difficult to check spot.  I use the spray method when I keg a beer and use the pressure gauge method periodically or if I otherwise suspect a problem.

Post O-Rings!

For the most part, what we’re checking with the “Pressure Gauge Method” are the keg’s gas o-rings.

I’m quick to replace these o-rings in general.  Beyond slow and no-carbing beers, a bad gas o-ring can lead to empty tanks, which are… not fun.  Grab Post O-Rings in Bulk to have on hand

Valuebrew carries color coded post o-rings… “Green for Gas” and “Blue for Beer” they also carry pin lock post o-rings in bulk,  Search “Post” at Valuebrew to see full lineup.

Related – Star San, Fixing Keg Leaks & More

The Pressure Gauge Method… without a Pressure Gauge

Another option if you don’t have a spunding valve or other gauge (but do have a two gauge regulator) is to attach only one keg to your regulator and turn off the the CO2 tank.  This allows you to use the low pressure gauge to monitor the keg.  The benefit of this method is that you’re testing everything – line, manifold, QD, o-ring and keg.

Some downsides to this…

  • You’re taking your other kegs offline
  • It somewhat complicates things as you’re testing more than just the keg in question
  • Most regulators… will not hold pressure long term. I’ve found that when pressure is not being applied from the high pressure side, regulators will slowly leak CO2. My guess is that this is by design. So, without a standalone pressure gauge, you can only check for moderately fast leaks using the low pressure side of your regulator.

Simple Assembly if you Don’t Want a Spunding Valve

If you’d like a gauge but don’t want the full features of a Spunding Valve, two Kegland items will give you a simple pressure gauge.

This gauge gauge and fitting will help you turn you MFL ball lock or pin lock QD into keg pressure testing gauge.

Related: Hands on Review: Kegland DuoTight Fittings & EVABarrier Tubing!

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Make sure the components you use are compatible and rated for your intended application.  Contact manufacturer with questions about suitability or a specific application.  Always read and follow manufacturer directions. toppost:co2leaks rp:tips6 tag:tpr

2 thoughts on “Checking for Draft System CO2 Leaks – Using The Pressure Gauge Method

  1. Gary Johnson

    I have conflicting info on the regulator / valve test with set 12 low side then off to 0. The pressure always will drop on the valve to 0 to indicate the setting. This was told to me by the manufacturer. So is there a leak through the regulator or not?

    1. admin Post author

      Hey Gary! I think that’s by design. The lower pressure side doesn’t seem to hold pressure long term. So, the low pressure side of your regulator workaround is really only helpful for checking for moderately quick leaks. I suggest getting/building a spunding valve or building a simple assembly.


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