Legionella and shower heads: why the last few inches of pipe get so much attention

Ask about legionella and shower heads and most of what you find is someone selling filter heads. This page sells nothing and explains why the shower head gets attention in building programs.

Why showers come up at all

Exposure to legionella is generally associated with breathing in small water droplets. Showers make exactly that kind of spray, in an enclosed space, close to a person’s face. That is the whole reason they appear in guidance more often than a kitchen tap does.

What happens inside the head

Between uses, a shower head and its hose hold a little water at room temperature. The inside surfaces develop biofilm and can collect scale. Neither is visible from outside, and neither says anything about legionella on its own. They are conditions that can favor it, which is the level at which a program works.

The rarely used shower is the one that matters

A shower used every day has its water replaced every day. A shower in an empty hotel room, a staff changing room nobody uses, or a ward bay that was closed for a month has not. When it is finally turned on, the first water out is the water that sat there. This is why programs for hotels and healthcare buildings pay attention to occupancy and to flushing routines for unused rooms, as set out on the hotel page. A shower nobody uses is, in effect, a branch with no flow, the same problem described in dead legs in building plumbing.

Cleaning, descaling and replacement

Many programs include periodic cleaning and descaling of shower heads and hoses, or replacement on a schedule. Frequencies differ by building and by the guidance a facility follows, and this page does not set one. What matters is that the routine is written down, assigned to a named person, and recorded when done.

Filters on the head

Point-of-use filters are used in some settings, particularly some healthcare areas. They are a control measure with their own maintenance needs and a stated service life. Whether they are appropriate is a decision for the facility and its advisers, not a purchase to make from an advertisement.

Showers and sampling

A sample taken at a shower can describe the head, the hose, or the system behind them, depending on how it is drawn. That difference is explained in water sampling for legionella. A shower result needs to say which of those it is about.

At home

A domestic shower is not covered by any building program. Running a shower that has not been used for a while before stepping in, and keeping the head clean, are common sense. Anyone worried about their health should speak to a doctor.