Topic
CO2, leaks, temperature, and the things that flatten your beer.
Flat beer from a kegerator is the inverse of the foaming problem, and almost as common. The beer pours fine — no head, no fizz, drinks like it's been sitting in a pint glass for an hour even when you've just poured it. Frustrating, especially when you've just paid £180 for a 50L keg.
Flat beer is almost always one of: (1) CO2 pressure too low for the beer style, (2) a CO2 leak somewhere in the system, (3) keg has been on gas too long at too low a pressure (under-carbonated), or (4) the beer itself was already old when you got it. The first three are fixable. The fourth means you need to find a better keg supplier.
Every flat-beer diagnostic we've written, organised so you can rule causes out one at a time without wasting an afternoon.
Flat beer isn't 'no CO2 in the line', it's not enough CO2 dissolved in the beer. Different problem, different fix. The 5 causes and how the timeline tells you which one.
The four usual suspects: CO2 pressure too low (under 8 PSI for most beer styles), undetected CO2 leak (check your regulator gauge — if it drops overnight, you have a leak), keg under-carbonated from the start (some kegs leave the brewery low), or the beer is genuinely old (lager loses fizz over months). Pressure-test the system first; investigate the keg second.
The soapy-water test: mix a bit of washing-up liquid with water in a spray bottle, spray every joint and connector while the system is pressurised, watch for bubbles. Most leaks are at the regulator-to-tank connection (re-seat the washer) or the gas-line-to-coupler quick-disconnect (loose, or the o-ring is gone). Tighten or replace as needed. Re-test.
Yes. Crank the CO2 pressure to 25-30 PSI and leave the keg in the fridge for 24-48 hours. The dissolved CO2 will rebuild. Drop pressure back to your serving pressure (10-12 PSI), wait an hour for the lines to settle, and pour. This is called "force carbonation" and it's how brewers carbonate kegs in the first place.
A properly sealed keg under pressure (10-12 PSI) holds carbonation indefinitely — months, years. Once you tap and stop pressurising, dissolved CO2 starts leaving the beer within hours. If your kegerator can't maintain pressure, you'll have flat beer in 2-3 days. Keep gas on the keg continuously.
Yes, but not in the way you might think. Warmer beer (above 45°F) releases CO2 faster, so it can taste flat sooner. Colder beer (under 36°F) holds CO2 better but slows the rate at which CO2 reaches your tongue, so it can also taste flat. The sweet spot for most beers is 38-42°F.