Draught Systems and Dispense
This domain tests whether you can balance a draught system, pour correctly, and diagnose foam and flatness instead of guessing.
Core rules
- Push pressure must equal resistance: line length and diameter, lift, and faucet resistance. Approximate resistance: 3/16" vinyl ~3 psi/ft; 1/4" barrier ~1.2 psi/ft; lift ~0.5 psi/ft; faucet ~1–2 psi.
- Hold kegs at 38°F for standard dispense; warmer beer releases CO2 and foams.
- Standard CO2 dispense at 38°F and 12 psi gives roughly 2.5–2.6 volumes.
- Nitrogen dispense uses 70/30 or 75/25 beer gas at high pressure (often 30–35 psi) with a restrictor plate or sparkler for nitro stouts.
- Couplers: D (American Sankey), S (European Sankey), A (German slider), G (Grundy), U - match the keg, not the brewery's home country.
- Clean lines every two weeks with a dedicated line-cleaning chemical, then rinse thoroughly. Keep the FOB functional.
Worked example
At 38°F you want 12 psi at the keg, with 8 ft of 1/4" barrier line and the faucet 1 ft above the keg. Resistance = (8 × 1.2) + (1 × 0.5) + 1.5 faucet ≈ 11.6 psi, so 12 psi is nearly balanced - expect a clean pour. If the line were 5 ft of 3/16" (15 psi of resistance) at 12 psi, the beer would arrive flat and slow; too short a line would foam from pressure drop.
Traps that cost marks
- Turning pressure up to cure foam caused by warm lines or a short run.
- Ignoring lift when the tap is upstairs or across a long run.
- Using pure CO2 on a nitro stout, or beer gas on a standard ale.
- Serving through dirty or uncleaned lines - foam, off-flavors, and lost carbonation.
- Pouring into a glass with residual detergent or grease, which kills the head.