Every pint leaves a little something behind. Beer carries sugar, protein, and yeast. A thin film of that stays on the inside of the line after each pour. Bacteria and wild yeast live on it.
Left alone, those bugs build a slimy layer called biofilm. It sticks to the tubing wall and keeps growing. It changes how the beer tastes and how it pours. Two weeks is the longest the industry says you should let it go.
Where the 14 Days Comes From
The Brewers Association Draught Beer Quality Manual says to clean draft lines at least every two weeks. That manual is the reference the whole trade works from.
Pennsylvania made it law. 40 Pa. Code § 5.51 requires lines, couplers, and other parts to be cleaned once every 14 days. The state moved from a 7-day rule to 14 days in 2021, which lined it up with the Brewers Association.
What Grows in There
The Brewers Association names the usual suspects: Lactobacillus, Pediococcus, Pectinatus, and Acetobacter. They ruin flavor. The Brewers Association notes they are not a health risk. Lactobacillus and Pediococcus bring sour notes and a buttery flavor called diacetyl. Acetobacter turns beer toward vinegar.
The flavor gets worse as the biofilm grows. Regulars pick up on it. Most won't say anything. They'll order a bottle next time. Our guide to off-tastes in draft beer covers how to tell these flavors apart.
Why Monthly Doesn't Cut It
A lot of bars still run on a monthly schedule. That puts the lines past due for half of every month. The biofilm also gets thicker between visits, so each cleaning has more to strip off.
What a Cleaning Should Include
Running water through the lines between kegs is a rinse. It moves loose gunk. It won't touch biofilm. A proper cleaning per the Brewers Association looks like this:
- Push the beer out of the lines.
- Take the faucets and couplers apart and scrub them by hand.
- Pump caustic line cleaner through the lines for at least 15 minutes. The mix is 2% for routine cleaning and 3% for dirty lines. The solution should be warm, 80 to 110°F.
- Rinse with clean water until no cleaner is left.
- Put the parts back together and run beer through before serving.
Once a quarter, an acid cleaning follows the caustic to remove beer stone. See what beer stone is for why.
Write It Down
Pennsylvania wants proof. If someone else cleans your lines, you need a certificate with the date, their name, and the method. Keep it at the bar. The details are in draft line cleaning records.
If your lines have gone longer than two weeks, call us at (267) 282-1002 and we'll get you back on schedule.