Draught line cleaning

Why the line matters as much as the keg

A keg of properly brewed beer travels through a coupler, a line, sometimes a python bundle of several lines, and a tap before it reaches a glass. Every one of those surfaces is wet, dark and at cellar temperature, which happens to be an excellent environment for bacteria and wild yeast to build a film if it is not cleaned regularly.

A brewery can control every variable inside its own walls and still lose all of that work at a bar with a poorly maintained line. This is one of the least visible parts of the whole supply chain, and one of the most consequential for how the beer actually tastes in the glass.

What beer stone actually is

Beer stone is a hard, calcium based deposit that builds up inside a line over repeated pours, and it is not just a surface problem. It creates a rough, pitted texture that bacteria and yeast can shelter inside, well past what a normal rinse or even a standard cleaning cycle can fully remove.

Once established, beer stone makes every future infection risk worse, because it gives contaminants somewhere to hide between cleanings. A line with heavy beer stone build up often needs a dedicated descaling step before a normal caustic cleaning cycle can be fully effective again.

What a dirty line does to the flavour

The most common result is a sour or off note that has nothing to do with how the beer was brewed, similar to the fault covered in our guide on infection related sourness. Flat or excessive foam, and a general staleness that does not match a fresh keg, are also common signs.

Bar staff sometimes blame the keg or the brewery first, when the actual cause never left the building, which delays fixing the actual problem while a perfectly good keg gets returned unfairly.

How often lines should actually be cleaned

Industry guidance generally points to a full clean roughly every two weeks for a line in regular use, more often for high volume taps or lines carrying beers with dairy or fruit adjuncts that leave more residue behind. A line that sits unused for a stretch needs cleaning again before it goes back into service, since standing beer left in an idle line accelerates bacterial growth.

Indian heat makes idle lines a bigger risk than in a cooler climate, since warmer ambient temperatures around the bar area speed up whatever is already growing in an uncleaned line.

A brewery opening a new taproom or a bar adding its first set of taps often underestimates this schedule at the start, treating it as an occasional task rather than a fixed recurring one on the same footing as any other food safety routine.

What proper cleaning actually involves

A real clean uses a caustic based line cleaning solution circulated through the entire system, coupler, lines and tap faucet, for a set contact time, followed by a thorough rinse before beer goes back through. Simply flushing a line with hot water is not the same thing and will not remove beer stone or an established biofilm.

Many bars keep a signed log of cleaning dates for exactly this reason. It turns an invisible maintenance task into something a manager can actually verify happened, rather than trusting that it was done from memory.

The faucet itself is often the most neglected part of the whole system, since it is easy to focus attention on the long line and forget the small assembly the beer actually pours through last.

What to look and taste for as a customer

A pint that tastes noticeably different from the same beer in a can or bottle, especially with a sour or musty edge, is worth mentioning to the staff. A bar that takes its lines seriously will usually know exactly when the last clean happened and will not be defensive about the question.

This is one of the few faults where a polite question to staff genuinely helps everyone, since a bar that only finds out about a problem from a review rather than a conversation loses the chance to fix it before the next customer notices too.