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.

Related: Step by Step: Finding and Fixing Keg CO2 Leaks

A Problem Spot…

Color coded post o-rings. From our Keg Rebuild Post – Jump To: Replace O-Rings

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.

In my opinion the most difficult spot to check and the cause of many a lost CO2 tanks are… gas post o-rings.

Testing at this point using the “spray bottle method” (spray Star San everywhere and check for bubbles) is impossible or at the very least difficult and messy.  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 is on.

The problem 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.

Be quick to replace gas side o-rings… I’m quick to replace gas post (and gas dip tube) o-rings. Beyond slow and no-carbing beers, a bad gas side o-ring can lead to empty tanks. That’s a waste of time and money and it’s frustrating.

These o-rings cost pennies each when you buy them in bulk. Liberally replacing these can save time, money and frustration.

The Pressure Gauge Method!

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.

Testing Single Kegs Using Digital Keg Pressure Tester:

Digital Keg Pressure Tester

This combines a Kegland Ball Lock QD with a DuoTight 0-90 PSI Digital Pressure Gauge to for a digital keg pressure gauge. These have lots of uses, including checking for CO2 leaks and monitoring keg pressures.

This setup works even if – gasp! 🙂 – you aren’t using DuoTights as your draft fitting system.

Kegland’s DuoTight system along with their EVABarrier Tubing are amazing. Check out my extensive hands on review for a deep dive into the system.

This is a good option to check single kegs using the pressure gauge method.

Digital Keg Pressure Tester

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

Another Layer of Protection – Using a CO2 Monitor to Check for Kegerator CO2 Leaks

Thanks to HBF Reader Elliott for this tip!  Let’s be friends!  8 Ways to Connect with HBF

INKBIRDPLUS Indoor CO2 Detector, Air Quality Monitor, Tester for Carbon Dioxide, Temperature and Relative Humidity, Indoor CO2 Monitor with Alarm, for Grow Tents, Wine Cellars, Homes, Cars(PTH-9C)

Pictured: INKBIRDPLUS Indoor CO2 Detector

Placing a CO2 Monitor with alarm inside of your kegerator can serve as another line of defense to protect against co2 leaks and loss. CO2 should not be building up in your kegerator. A CO2 monitor with alarm can alert you of this condition.

This is not a replacement for the steps outlined here, rather a another layer that could save you a trip to swap out a CO2 tank.

Closely Related:

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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. tag:lnksfxd toppost:co2leaks rp:tips6 tag:tpr

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

  1. Mariano P.

    Hi, my keg has a leak on welding zone, bellow the rubber base, I can see bibles between rubber and steel line on keg’s bottom around rubber/metal union. So.. I don’t think rubber base could be taken off and weld, and you can’t put an arm and see what you are welding inside.. So¿is there any material to seal the leak?? Like epoxy or something? Preferentially food safe but if not it is good anyway because I’m giving an mom food/drink use. It seems the leak is not big because I can see a punch ofbubbles under water so.. ¿Any suggestions beside call the manufacturer who died or /and live in other continent? Thanks!

  2. 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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