The brewery carbonated that keg correctly. If it pours flat, something between the keg and the glass let the CO₂ out. Work through these checks in order.
1. Check the CO₂ Pressure
Low pressure is the most common cause. For most ales and lagers at 38°F, the regulator sits around 12 to 14 psi. The exact number depends on how carbonated the beer is. The Brewers Association Draught Beer Quality Manual has charts for it. If the gauge is low, set it back and give the keg a few hours to settle before you judge it.
Look at the CO₂ tank too. A tank close to empty can still show pressure at the regulator and then fall off when you pour a lot. If it's low, swap it before you chase anything else.
2. Check the Temperature
Cold beer holds CO₂. Warm beer lets it go. The Brewers Association says to keep the cooler at 38°F.
Check it with a thermometer in a glass of water that's been sitting in the cooler. The dial on the door can be off. Then check the beer at the faucet. Put a thermometer in the first pour of the day. If it's much warmer than the cooler, the beer is warming up on the way to the tap.
On long-draw systems, the lines run through walls or ceilings to the bar. They need a glycol chiller to stay cold the whole way. If the glycol is off or low, the beer warms up and goes flat or foamy.
3. Look for Gas Leaks
A slow leak on the gas side drops your pressure without any obvious sign. To check:
- Close the valve on the CO₂ tank.
- Write down the reading on the regulator.
- Come back in an hour. If the reading dropped, you have a leak.
- Open the tank and spray soapy water on every gas fitting. Bubbles show you where it's escaping.
4. Check the Gas Blend
Some bars run a nitrogen and CO₂ blend, often 75% nitrogen and 25% CO₂, for stouts and nitro beers. Put a regular ale or lager on that blend and it slowly loses carbonation. Make sure each beer is on the gas the brewery recommends.
5. Look at the Lines
Dirty or crusty lines give CO₂ rough spots to break out of the beer. The beer foams at the faucet, the foam settles, and what's left in the glass tastes flat. If flat and foamy show up together, look at the causes of foamy beer and check when the lines were last cleaned.
Still Flat?
If pressure, temperature, gas, and lines all check out, the system needs someone to look at the whole thing. Call (267) 282-1002.