HAVERHILL — A rookie line cleaner disconnected a keg, dismantled the faucet and keg coupler, and connected the cleaning can to one of the lines that link kegs to taps at the AMVETS bar here. Sporting a pair of protective rubber gloves, he ran an alkaline solution through the draft line and began washing the disassembled parts with the same teal-colored cleaner, while his more practiced colleague narrated like the voice-over of a surgical drama.

It was a routine draft-line cleaning — the first stop on the men’s route through Northern Massachusetts. While the faucets air-dried, military veteran Shaun Murphy described the microscopic beasts that breed in lines left unchecked. “I can walk into a place and smell whether the taps are clean,” said Murphy, who since 2013 has been cleaning lines for Tibs Taps, a company that installs and maintains draft beer systems; he placed his fingers under the water that now ran through the lines, turning from green to clear as the chemicals dissipated.

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While rare, there has been at least one documented case in Massachusetts where a beer distributor failed to flush out the caustic cleaning solution from the draft lines, injuring a patron who suffered burns on her throat. Like the one that Tibs Taps uses, many cleaning solutions now contain color pigments to easily identify whether the lines are completely free from the solution before drawing beer from the tap.

Massachusetts law places responsibility on the bar or restaurant, rather than the distributor, for ensuring draft beer lines are clean and safe, but like similar laws in most states, the regulation is relatively unenforceable until an individual files a complaint or the business is subject to inspection.

Read the rest at BostonGlobe.com.