Two weeks is the maximum interval between draft beer line cleanings — not a suggestion, not an industry preference. It's the standard set by the Brewers Association and it's codified in Pennsylvania law. Here's why that interval exists and what happens when you stretch it.
What Builds Up Inside Draft Beer Lines
Beer is organic. It contains proteins, sugars, and yeast. Every time beer moves through a line, it leaves trace residue on the inner wall. That residue doesn't just sit there — it feeds microbial growth.
Within 48 to 72 hours of a cleaning, microorganisms begin colonizing the line wall. By day seven, a thin biofilm layer is established. By day fourteen, that biofilm is mature enough to measurably affect beer flavor. A 2021 study published in PubMed confirmed that bacterial biofilm in draft lines produces off-flavor compounds including acetic acid and lactic acid — the same acids responsible for vinegary and sour notes in contaminated beer.
Beyond biofilm, yeast deposits and beer stone (calcium oxalate) accumulate on the line wall over time. These don't taste like anything on their own, but they provide surface area for bacteria to attach and make the line harder to clean effectively with each passing cycle. [INTERNAL LINK: what is beer stone and why does it ruin your draft lines]
What the Brewers Association Recommends
The Brewers Association Draught Beer Quality Manual sets the cleaning interval at every two weeks — defined as no more than 14 days between cleanings. That recommendation is based on the rate at which biofilm matures to the point of affecting beer quality under normal serving conditions.
The manual specifies that a proper cleaning uses an alkaline detergent solution — typically caustic-based — circulated through the lines at the correct concentration and contact time. Flushing lines with water or beer between kegs is not a cleaning. It removes loose sediment but does nothing to biofilm on the line wall.
What Pennsylvania Law Requires
In Pennsylvania, the two-week cleaning standard is a legal requirement, not just a best practice. PA Code Title 40, Chapter 5, Section 5.51 requires that all malt beverage dispensing equipment be kept clean and sanitary. The Pennsylvania State Police Bureau of Liquor Control Enforcement interprets this to include adherence to the Brewers Association's two-week interval standard. Inspectors can and do check cleaning logs during routine license inspections. [INTERNAL LINK: Pennsylvania draft beer line cleaning law]
Failure to maintain clean lines can result in a citation, a fine, or — in serious cases — action against your liquor license. It also exposes you to liability if a customer becomes ill and the source is traced to contaminated draft equipment.
Why Monthly Cleaning Isn't Enough
A lot of bars get cleaned once a month. Some distributors still offer monthly service. That schedule is not compliant with PA law and it produces noticeably worse beer in weeks three and four of the cycle.
By day 21 or 28, biofilm in uncleaned lines has had time to produce significant concentrations of off-flavor compounds. Customers may not identify the problem as dirty lines — they'll just decide your draft beer tastes off compared to somewhere else. That's a loss you don't see on a ledger but you feel it in draft sales over time.
The two-week standard exists because the science supports it. Biofilm doesn't mature on a monthly schedule. It matures on a two-week schedule.
What a Proper Two-Week Cleaning Covers
A compliant cleaning isn't just pushing cleaner through the beer line. Every component that contacts beer needs to be broken down, cleaned, and sanitized. That means the faucet, the coupler, the jumper lines, the shank, and the main run of line from keg to tap.
The alkaline cleaner needs to stay in contact with the line wall long enough to break down protein and yeast deposits — typically a minimum of 15 minutes of contact time, per the Brewers Association guidelines. After cleaning, the lines are flushed and sanitized before beer is reintroduced.
A cleaning that takes less than 20 to 30 minutes per line is almost certainly cutting a corner somewhere. [INTERNAL LINK: alkaline vs. acid draft beer line cleaning]
Keeping a Cleaning Log
Pennsylvania bars are expected to document their cleanings. A cleaning log should record the date, the lines cleaned, the cleaner used, and who performed the service. If you're using a professional service, get a record from them after every visit. If the PLCB walks in, you want to be able to show a complete log going back at least 90 days. [INTERNAL LINK: how to read your draft beer cleaning log and why the PLCB cares]
The Bottom Line on Cleaning Intervals
Two weeks is the interval because that's when biofilm becomes a beer quality problem. Pennsylvania law requires it. The Brewers Association recommends it. Stretching that interval costs you beer quality, puts you out of compliance, and over time, costs you customers.
If your current cleaning schedule isn't hitting every two weeks, it's time to fix that. Call Philly Draft Cleaners at (267) 282-1002. We serve bars and restaurants across Philadelphia and the surrounding area.