How to Use a King Keg — Complete Guide to Pressure Barrel Home Brew

What is a King Keg and how does it work?

A King Keg is a 5-gallon (23-litre) plastic pressure barrel used to condition and serve home brew beer. After primary fermentation in your fermentation vessel, you transfer your beer into the King Keg with a small amount of priming sugar. As the residual yeast consumes this sugar, it produces CO₂ — building gentle pressure inside the sealed barrel, carbonating the beer naturally. You then serve beer through the tap at the bottom, with the pressure cap maintaining serving pressure as the barrel empties.

What do you need to use a King Keg?

• A King Keg pressure barrel with tap
• A King Keg pressure cap (with CO₂ bulb holder) or standard pressure cap
• CO₂ bulbs (for the pressure cap) — optional for natural conditioning, essential once you're serving
• Brewing sugar for priming — approximately 80–85g per 23 litres for a British ale
• Steriliser — everything must be thoroughly cleaned and sterilised
• A hydrometer to confirm fermentation is complete before transferring

Step-by-step: how to fill a King Keg

Step 1 — Confirm fermentation is complete. Take two hydrometer readings 24–48 hours apart. If the gravity is the same both times and matches your kit's expected FG, fermentation is done. Never transfer early.

Step 2 — Sterilise everything. Thoroughly clean and sterilise the King Keg barrel, tap, cap, and any siphon equipment using Young's Steriliser. Rinse well with cold water.

Step 3 — Prepare your priming sugar. Dissolve 80–85g of brewing sugar in 200ml of boiling water. Allow to cool completely before adding to the keg. Use our Priming Sugar Calculator for the precise amount based on your batch size and target carbonation.

Step 4 — Transfer your beer. Add the cooled sugar solution to the empty, sterilised King Keg first. Then siphon or tap your beer on top — transferring gently to minimise splashing and oxygen exposure. Leave 5–8cm of headspace at the top.

Step 5 — Seal and condition. Fit the pressure cap firmly and store in a warm place (18–22°C) for 3–5 days to allow the secondary fermentation to build carbonation. Then move to a cool location for a further 7–10 days to condition and clear.

Step 6 — Serve. Your beer is ready when it has been conditioning for at least 2 weeks total. Open the tap slowly — your first pour may be slightly cloudy as it disturbs the yeast sediment on the bottom. Subsequent pours should be clear. As the barrel empties, use a CO₂ bulb in the pressure cap to maintain serving pressure.

How much priming sugar goes in a King Keg?

For a standard 23-litre batch of British ale, use 80–85g of brewing sugar (dextrose) or 70–75g of plain table sugar. For a lager or more highly carbonated style, use 90–100g. Always use our Priming Sugar Calculator for exact quantities based on your specific batch.

Why is my King Keg beer flat?

Flat beer from a King Keg is almost always one of three things: the barrel wasn't sealed properly and CO₂ escaped; not enough priming sugar was used; or the beer was served before conditioning was complete. Check the cap seal is tight, ensure you've allowed at least 2 full weeks, and fit a CO₂ bulb to restore pressure when serving. Also check the tap seal — a weeping tap loses pressure gradually.

How do CO₂ bulbs work with a King Keg?

CO₂ bulb caps for the King Keg allow you to inject CO₂ gas into the headspace as you pour, maintaining serving pressure and preventing the beer going flat as the barrel empties. Without a CO₂ bulb, the first few pints pour well but the last few can be flat and slow. Fit a bulb once the barrel is around half empty for best results.

Browse our full range of King Keg pressure barrels and spare parts at BrewCo UK. Also see our Priming Sugar Calculator and Keg Line Balancing Calculator.