Draft Beer Troubleshooter
Foamy beer? Flat pours? Strange taste? Draft beer problems are almost always fixable once you know the cause. Select your symptoms below and this troubleshooter will walk you through a step-by-step diagnosis — the same process used by professional draft technicians and outlined in the Brewers Association Draught Beer Quality Manual.
Select Your Symptoms (choose all that apply)
Off-Flavor Quick Reference
Use this table when your beer tastes or smells wrong. These are the most common draft off-flavors and their causes, per the BA Draught Beer Quality Manual.
| Flavor / Aroma | Description | Most Likely Cause | Fix |
|---|---|---|---|
| Diacetyl (butterscotch) | Slick, buttery, butterscotch taste | Dirty lines, warm fermentation, or yeast issue | Clean lines immediately. May be a brewery issue if freshly cleaned. |
| Acetaldehyde (green apple) | Green apple, cidery taste | Under-fermented beer or bacterial contamination in lines | Clean lines. Verify fresh keg. Contact brewery if persistent. |
| Oxidation (cardboard / sherry) | Cardboard, stale, sherry-like | Air in gas supply, old keg, or oxygen exposure | Verify pure CO2 or certified beer gas. Never use air or hand pumps. Check keg date. |
| Sulfur / DMS (cooked corn) | Cooked vegetables, corn, sulfur | Dirty faucet or coupler, or brewery/yeast issue | Clean and sanitize all contact points. Soak faucet in BLC cleaner. |
| Sour / Acetic (vinegar) | Sharp sourness, vinegar | Bacterial infection — Lactobacillus or Acetobacter in dirty lines | Clean lines IMMEDIATELY. May need caustic cleaner. Replace old line. |
| Musty / Moldy | Musty, earthy, damp basement | Mold or wild yeast in lines, tap, or drip tray | Full system cleaning. Scrub drip tray. Inspect and replace gaskets. |
| Skunk / Lightstruck | Skunky, rubber, burnt rubber | UV light exposure to clear or green bottles/kegs | Keep kegs in dark cooler. UV exposure skunks beer in as little as 30 minutes. |
| Metallic | Blood-like, metallic taste | Old or corroded lines, worn couplers, or stainless issues | Replace beer line. Inspect coupler and fittings for corrosion. |
Line Cleaning Rule: The Brewers Association requires beer lines be cleaned with an approved alkaline cleaner at the proper concentration every 14 days minimum. Most off-flavors that develop within 1–2 weeks of a clean pour are line-cleaning issues. — BA Draught Beer Quality Manual, 4th Ed.