Part of the Beer Mastery school. Class 3 of 6.
The capability: you know when the lines were last cleaned and you can prove it.
Prerequisites: Module 32.
The practice
Ask when the lines were last cleaned and by whom. Any uncertainty is the finding.
Then disassemble a faucet and look inside. That is the argument for including them in the cycle and it does not need to be made twice.
Then taste the lightest beer on the system weekly — it is the canary, because it has no malt sweetness, hop bitterness, or alcohol to mask a faint acid edge.
And run the sheeting test on glassware, per Module 32, because detergent film is a separate and equally invisible problem.
The reference
The bottled version, again — and a clean faucet's interior against a dirty one.
What you are building
The understanding of why nobody in the building notices.
The buildup is gradual and everyone on staff is calibrated against yesterday — which means the detection system is a guest's memory, per Module 32, and that is the problem rather than a feature.
And the ownership conclusion: a schedule assigned to everyone is assigned to nobody.
Verification and boundary
A logged cleaning date with a named owner. A cleaning that was not logged cannot be proven.
Boundary: line cleaning chemicals are hazardous and their handling is governed by the manufacturer's instructions and applicable safety requirements. The an independent draft-quality authority manual is the technical authority on chemistry, contact time, and interval.