Step by Step: Finding and Fixing Keg CO2 Leaks

Pictured: Brand New 5 Gallon Ball Lock from Adventures in Homebrewing

A leaky keg can be an issue, a big issue.  That nice, full CO2 tank can go away in short order.  It’s frustrating, costly and inconvenient.  This post should help you them and fix them.

Start with a solid system

When you setup your kegerator, make sure your regulator, manifold and all connected lines are solid to begin with.  Spray components down and check for leaks.  The low pressure gauge on your regulator can be a help diagnosing overall system health.  Turn off the CO2 tank and watch for changes in pressure.  A drop means something is leaking.

  1. Every time.  If your keg could have opinions (it cannot), I would venture a guess that it does not care how leak free it was the LAST time you used it.  Check your kegs for CO2 leaks every time you use them.
  2.  Poorly seated keg lids.  An easy to do and easy to fix problem is a poorly seated keg lid.  One trick I’ve developed is leaving the handle disengaged when pressure is first applied.  Here’s what I do – insert and orient the keg lid and lift up and the lid handle and apply CO2 pressure.  This leaves the lid loose enough to seat properly.  When the keg headspace pressurizes, I engage the handle to lock the lid into place.
  3. Pressurize and test at serving pressure.  If you pressurize and test at unrealistically high PSI you’re not really getting a good picture of how your keg performs at serving pressure.  Stated another way – a keg may be completely tight and leak free at 30 PSI, but have a leak at 10 PSI.
  4. After pressurizing your keg, take a listen.  Fast leaks can often be heard.  This may save you some Star San, some CO2 and some time.  If you don’t hear anything, proceed.
  5. Star San is your friend.  After pressurizing at serving temperature and listening for leaks, liberally coat the keg lid and posts (both base and top) with properly diluted Star San using a spray bottle.  Look closely for bubbles.  If you’re unsure, keep looking and spraying.  Want to know how to mix a single gallon of Star San?  See: Star San Tips, Tricks and Guidelines.  Wipe down the keg when you’re done.
  6. There is one place that the “Spray Bottle Method” doesn’t really work…. the keg’s gas post.  That spot is only in play when your gas QD is engaged.  The kicker is… when the gas QD is on, you can’t see underneath it to check for bubbles.  The offending part at this point, in my experience, is usually gas post o-ring.  A small crack on this small, very cheap gasket has sent me to refill my CO2 tank on two occasions.  Since learning this lesson, I am quick to replace gas side o-rings.  See: Keg Repair Part #s.  I have developed a technique, that I’ve dubbed “The Pressure Gauge Method” of checking for keg lids that I use to check the entire keg, including the gas post o-ring.  Keep reading for that.  Note: This same spot is equally difficult to check on the liquid side, however, leak on that side are evident… your indication will be… beer leaking.  See more about the Pressure Gauge Method below.

Tip: Why Won’t My Homebrew Carbonate?

Ever have a beer that just doesn’t want to seem to carbonate in the keg?  Either it just doesn’t carbonate or it does so very slowly.  In my experience, this could be an indication of a CO2 leak.  Pressurized gas is going to take the path of least resistance.  It’s easier to leak than it is to dissolve into solution.  Even a small leak can slow down or seem to stop the carbonation process.  A quick synopsis of how I learned this:  My beer is not carbonating as I expect it to, wait… empty CO2 tank!  Fill tank, repeat.  My beer is not carbonating as I expect it to, wait… empty CO2 tank!  Fill tank, replace gas post o-ring, repeat… beer carbonates normally and my CO2 tank does not magically empty.  I’m not saying this is always the cause – temperature, pressure and time are all factors, but if you’ve having problems getting draft beers to carbonate, it’s something to consider.

See: Why Won’t My Homebrew Carbonate? Fixing Beer Carbonation Problems for lots more info.

The Biggest Trouble Spot

In my experience, hard to find leaks and carbonation problems are usually caused by the gas post o-ring.  I suggest changing these regularly.  A few cents for an o-ring, saves a lot of time, money and frustration refilling a CO2 tank.

From our Keg Rebuild Post – Jump To: Replace O-Rings

Valuebrew carries color coded post o-rings in food grade silicone… “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.

The Pressure Gauge Method of Checking for CO2 Leaks

  1. Charge your keg with CO2 as usual using your typical serving pressure.
  2. Remove the CO2 line and replace with a pressure gauge [ball lock version via William’s Brewing] or Spunding Valve [Spunding Valve Build].
  3. After the pressure has stabilized. I mark the current pressure with a China Marker/Wax Pencil, or you can just remember what it reads
  4. Wait for a couple hours to overnight to see if the gauge drops.
  5. 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.
  6. This technique tests the entire keg including the gas post, o-ring, QD and any tubing that’s connected.
  7. 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.
  8. If you suspect a leak based on gauge movement, that is not otherwise evident.  I suggest starting with gas QD o-ring.

More About the Pressure Gauge Method… Checking for Draft System CO2 Leaks – Using The Pressure Gauge Method

Practically speaking, A use the “Spray Bottle Method” every time I put a keg into service and periodically double check everything with the pressure gauge method.

Find a Problem… Fix It!

Once you find a leak… fix it!  Most problems can be fixed by replacing parts – lid, post and dip tube o-rings, PRV valves, lids and poppets – all replaceable. See: Keg Repair Part #s

For O-Rings, you should consider food grade replacements

If your keg has a structural or safety related issue, stop using it immediately and contact the manufacturer with questions about repair or suitability for continued use.

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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:kegleaks tag:tpr rs:6

1 thought on “Step by Step: Finding and Fixing Keg CO2 Leaks

  1. dammad

    Leaks are a BIG problem when not detected. Lost 2 CO2 tanks before I Iearned. Now, besides checking every connection – every connection from the CO2 tank to the keg including the beer post with Star San, I use food grade petroleum grease on every lid seal adding it generously mount it and test. It works. I don’t align the lid and then pressure tested it and haven’t had any problem. Agree to test at serving pressure. Obviously, if only tested at high pressure, there is more pressure on the lid; so, its chances to look fine are good. Also, I’ve learned to use sugar – priming or table – in the keg to carbonate saving expensive CO2.


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