Draft Beer Troubleshooter

Draft Beer Troubleshooter | Foam, Flat Beer & Off-Flavor Fixes | Wholesale Beer Parts

Draft Beer Troubleshooter

Foamy beer, flat pours, off flavors — they're almost always fixable once you know the cause. Select your symptoms below and get step-by-step solutions from the Brewers Association Draught Beer Quality Manual, the same diagnostic process professional draft technicians use.

Why draft beer problems happen

Most draft beer issues trace to one of five root causes: temperature (beer above 38°F foams and goes flat), line balance (too short or too long), pressure (wrong CO2 PSI or gas blend), cleanliness (bacteria and yeast in lines ruin every pour), or glassware (a greasy glass kills foam instantly). The troubleshooter below walks through each symptom and what to check first.

Select all the symptoms you're seeing (foam, flat, off taste, slow pour, warm, hazy, CO2 waste, or no head retention), click Diagnose My System, and the troubleshooter ranks causes from most likely to least likely based on BA field data. Each fix includes actionable steps you can take with standard tools.

Select Your Symptoms (choose all that apply)

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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.

Frequently Asked Questions About Draft Beer Troubleshooting

What is the most common cause of foamy beer?
Temperature — beer above 38°F is the #1 cause of foam in draft systems. Even 2°F above target dramatically increases foaming. Check your cooler thermostat with a calibrated thermometer. After temperature, the next most common causes are lines that are too short (under-restricted), dirty lines, or serving pressure set too high.
Why does my beer taste like butterscotch or buttered popcorn?
That's diacetyl, a compound produced by yeast during fermentation. In draft, diacetyl most commonly appears because of dirty beer lines — bacteria and wild yeast produce diacetyl as they grow in the line biofilm. Clean your lines immediately with an approved alkaline beer line cleaner (BLC). If the beer was just tapped, the issue may be from the brewery.
How often should I clean my draft beer lines?
The Brewers Association standard is every 14 days minimum. High-volume bars pouring 20+ kegs per line per week should clean weekly. Lines that run nitro stout or high-ABV beer need more frequent cleaning because beer stone and protein buildup accelerates. Use an approved alkaline cleaner at the manufacturer's concentration — not just hot water.
Why is my pour slow even though pressure is correct?
Most likely causes: lines too long or too restrictive for the pressure, a clogged faucet (beer stone or yeast buildup in the spout), or a kinked beer line. Check the beer line for sharp bends. Disassemble and clean the faucet completely. Use the line balancing calculator to verify line length is correct for your system pressure.
A greasy glass ruins foam — how do I know if my glassware is beer clean?
A beer-clean glass shows sheets of fine bubbles rising evenly from all sides with no gaps or large patches. If bubbles cling to the sides or foam collapses quickly, the glass has residue. Wash with phosphate-free, unscented detergent only — no rinse aids. Air-dry upside down on a peg rack. Handle glasses by the stem or base only; skin oil kills foam.
Is it safe to serve beer that looks hazy or cloudy?
It depends. Intentional haze (NEIPA, hefeweizen, witbier) is normal. Chill haze from serving below 36°F is harmless and clears when the beer warms. But if you see thick, chunky, or stringy haze in a normally clear beer, it could be a bacterial or wild yeast infection in your lines — clean the system immediately. Slime or biofilm in lines is a food safety concern.

Need cleaning supplies or replacement parts?

We stock the full range of beer line cleaning chemicals — BLC, acid cleaners, alkaline washes — plus faucets, couplers, replacement O-rings, beer line, and all fittings. Same-day shipping from the Northeast for bars, breweries, and installers.

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Wholesale pricing available. Call 800-821-0114 for volume cleaning chemical orders.

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