A bad pour costs you twice: first in wasted product, then in the customer who orders a bottle next time. Draft beer is a perishable food product that travels through several feet of tubing, a gas system, and a refrigerated room before it reaches the glass — and every link in that chain can ruin it. The good news: most draft quality problems come from the same handful of causes, and all of them are preventable.
Whether you run a Boston pub with twenty taps or a restaurant with two, a draft system needs three things to pour clean: steady cold temperature, clean lines, and correct gas pressure. Get those right and the rest is details.
Temperature: Keep Beer at 36–38°F From Keg to Glass
Draft beer pours best at 36–38°F. Warmer than that and CO2 breaks out of solution — that's foam. Colder and you mute the flavor you're paying for. The entire path from keg to tap has to hold that range.
- Short draw vs. long draw. If your kegs sit directly under the bar (short draw), a blower pushing cold keg-room air up the tower is usually enough. If the keg room is downstairs or across the room (long draw), the beer travels through lines cooled by a circulating glycol system — and that glycol chiller is a piece of refrigeration equipment that needs the same care as anything else in your kitchen.
- Check the tower by hand. Touch the beer tower before service. If it feels room-temperature or sweats heavily while the chiller is running, the glycol pump, blower, or tower insulation needs attention.
- The keg room is a walk-in cooler. Dirty condenser coils, torn door gaskets, and iced evaporators raise its temperature exactly like they do in a food walk-in. Keep it at 36–38°F and maintain it like any other cooler.
Line Cleaning: Every Two Weeks, No Exceptions
The industry standard (Brewers Association) is a caustic cleaning every two weeks, plus an acid cleaning every quarter to remove beer stone (mineral scale). This is the single highest-return habit in draft maintenance.
Dirty lines don't just look bad — a biofilm of yeast and bacteria builds up on the inner walls, producing sour and buttery off-flavors and extra foam. By the time your staff can taste the difference, your regulars already have.
- Assign the schedule. Hire a line-cleaning service or train your staff — but either way, hold someone accountable for the two-week rhythm.
- Keep a written log with dates of every cleaning, caustic and acid. Logs also show up in health inspections and warranty conversations.
- Flush thoroughly after chemical cleaning and verify with pH paper — chemical residue is its own off-flavor.
- Never skip the quarterly acid cycle — beer stone does not come off with caustic alone.
- Replace tubing on schedule — vinyl lines typically every 1–2 years; barrier tubing lasts longer.
Gas Pressure: Balanced, Not "Turned Up"
CO2 pressure holds carbonation in the beer; the right setting depends on beer temperature and the brewery's carbonation level. At 38°F most ales sit around 10–14 psi — but that's a starting point, not a rule. Stouts and nitro pours use a nitrogen/CO2 blend (usually 70/30); never put nitro gas on a regular lager or straight CO2 on a nitro stout — you'll get a flat keg or a foamy mess either way.
- If foam appears suddenly, resist the urge to crank the regulator. Nine times out of ten the cause is temperature or dirty lines, and raising pressure just wastes gas and makes the next keg worse.
- Check regulators monthly. Gauges that creep up when no beer is flowing mean the regulator diaphragm is failing — replace it before it over-carbonates a keg.
- Check for leaks when swapping tanks. A 20-lb CO2 tank should last a busy bar weeks, not days. Brush soapy water on every connection; CO2 leaks are silent and expensive — and in a small basement keg room, a real safety hazard.
Foam Troubleshooting: A Quick Checklist
- Measure the pour temperature at the tap with a calibrated thermometer — 36–38°F is the target.
- Feel along the beer lines for warm spots, kinks, or crushed sections.
- Confirm gas pressure is at your system's set point (write it down when it's right, so you can compare).
- Check the line-cleaning log — more than two weeks since the last clean is a red flag.
- Rule out glassware — detergent residue, lipstick, or grease on a glass creates nucleation points and instant foam. Glasses must be "beer clean": rinsed, sanitized, air-dried.
- Let a freshly delivered keg rest 1–2 hours before tapping.
Keg Storage and Rotation
- Store kegs at 36–38°F and rotate first-in, first-out. Mark delivery dates on keg collars — unpasteurized draft beer is generally best within 30–45 days, and hoppy styles like IPAs fade even faster.
- Boston summers punish keg deliveries: a keg left on a hot dock for an afternoon arrives warm, and every warm-cold cycle shortens its life. Get deliveries straight into the cooler.
- Never let kegs freeze, and don't store them against heat sources — the compressor room wall is not a keg rack.
When to Call a Refrigeration Technician
- The beer tower or the keg cooler won't hold 36–38°F.
- The glycol chiller alarms, ices up, or runs constantly.
- You suspect a CO2 leak (hissing, tanks emptying fast, headaches or dizziness in the keg room — ventilate and call immediately).
- A regulator gauge creeps or won't hold a setting.
- Foam persists after temperature, cleaning, and pressure all check out — there may be a restriction or a failing component in the system.
Mini-FAQ
Why is only the first pint foamy?
The tower and lines warm up overnight (or between rushes). That first pour chills the line; after a few seconds of flow the rest pours clean. If every pint is foamy, the problem is elsewhere — work the checklist above.
Can we clean lines less often if we pour high volume?
No. Volume doesn't scrub biofilm off the tube walls — time does. The two-week schedule applies whether you pour a keg a day or a keg a week.
What temperature should the keg room be?
36–38°F, the same as the pour temperature. A keg room at 42°F will never pour a 38°F beer, no matter what the tower cooler does.
Is nitrogen better than CO2?
Only for beers brewed to be served on nitrogen. A standard ale or lager on a nitro blend will go flat; a nitro stout on straight CO2 will pour all foam. Match the gas to the beer.
How do I know the glycol system is failing?
Warm or sweating towers while the chiller runs, gurgling or silent pumps, chiller alarms, or beer temperature creeping up on long-draw lines. Glycol systems are refrigeration — treat breakdowns like a walk-in going warm.
Draft systems reward consistency: steady temperature, a two-week cleaning rhythm, and gas pressure you set once and check monthly. If your towers won't stay cold, pours are all foam, or the glycol chiller keeps alarming, that's a refrigeration problem — and it won't fix itself. Frostline Boston services draft beer systems, glycol chillers, and keg-room refrigeration across Greater Boston.