How do you clean shower heads to prevent legionella?
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Key points
- Showers are a priority outlet because they break water into a fine, breathable aerosol, which is the main route by which legionella reaches the lungs.
- The head and the hose sit warm, wet and full of scale between uses, giving legionella an ideal place to multiply.
- Quarterly cleaning and descaling is the usual starting frequency in HSG274 Part 2, adjusted up or down by your risk assessment.
- The method is remove, descale, disinfect by immersion, rinse and refit, following the disinfectant maker's contact time.
- Do not forget the hose, and treat little-used showers as the worst case: flush them weekly on top of the descaling routine.
To clean a shower head for legionella control you remove the head and hose, clear off the limescale, immerse both in a disinfectant for the stated contact time, rinse them with clean water and refit. The usual starting frequency is every three months, set by your risk assessment. Little-used showers also need flushing weekly.
Showers get singled out in legionella guidance for a reason. A tap fills a basin; a shower turns the same water into a cloud of tiny droplets that hang in the air and are easy to breathe in. That aerosol is the exact mechanism by which legionella bacteria reach the deep lung and cause infection, so any outlet that produces a spray moves to the top of the cleaning list.
Why the shower head and hose are such a good home for legionella
It is not only the aerosol. The head and hose have a second problem, which is that they stay warm and wet when the shower is off. Warm residual water sitting in the rose and the flexible hose lands squarely in the legionella growth range of roughly 20°C to 45°C. Bacteria that are harmless in fast-moving mains water get the still, tepid conditions they need to multiply.
Scale makes it worse. Shower heads clog with limescale, and that scale is not just a flow nuisance. The rough deposit shelters biofilm, the slimy layer where legionella lives, and it shields organisms from disinfectant. Rubber and flexible hose materials feed biofilm too. So a scaled-up head is doing three unhelpful things at once: holding warm water, growing biofilm and protecting whatever is in there from being cleaned out. This is why descaling is not optional cosmetic work. If you disinfect a head that is still full of scale, the disinfectant cannot reach the bacteria hiding underneath. You have to take the scale off first.
How often to clean and descale shower heads
HSG274 Part 2 gives a starting point of dismantling, cleaning and descaling shower heads and hoses roughly every three months, then letting the risk assessment fine-tune it. Quarterly is a default, not a legal fixed rule. If your water is very hard and heads scale up fast, or the shower serves people who are more vulnerable to infection, you clean more often. If a shower is heavily used, well designed and runs at good temperatures, the assessment may support a longer interval. The point is that the frequency is a decision you record and justify, not a number you copy blindly.
Whatever interval you choose, write it into the scheme and log each clean when it happens. An entry in the log book showing the date, the outlet and who did the work is how you demonstrate the task is actually being carried out rather than just planned.
The method, step by step
The recognised approach for a shower head and hose is straightforward:
- Remove the head from the hose and the hose from the wall fitting so you can work on both.
- Descale the head. Clear the nozzles and the internal parts of limescale using a proprietary descaler, following its instructions. Physical cleaning to shift visible scale and debris comes before any disinfection.
- Disinfect by immersion. Put the head and hose into a container of suitable disinfectant so every internal surface is covered, and leave them for the full contact time the maker specifies. Immersion matters because it reaches the inside of the hose and the back of the rose, not just the face you can see.
- Rinse both parts with clean water to remove the disinfectant.
- Refit the hose and head.
Some organisations keep a second, already-cleaned head and hose to swap in, then take the removed set away to descale and disinfect off site. That cuts the shower's downtime and lets the immersion run for as long as it needs. Either way, the sequence is the same: clean off the scale, then disinfect, then rinse.
Descale before you disinfect. Limescale shelters biofilm and blocks the disinfectant, so a head cleaned without descaling has not really been cleaned at all.
Do not forget the hose
The flexible hose is the part people skip, and it is often the dirtiest component of the whole shower. It is long, it holds a slug of water after every use, its ribbed inner surface is ideal for biofilm, and you cannot see inside it. A gleaming new head bolted onto an old, biofilm-lined hose is still an aerosol-producing risk. Treat the hose exactly like the head: remove it, descale it, immerse it in disinfectant for the full contact time, rinse and refit. If a hose is perished, split or heavily fouled, replace it rather than trying to rescue it.
Free legionella risk assessment template
A structured Word document following the five-step approach in ACOP L8. Covers risk identification, written scheme, monitoring, and records. If it isn't written down, you can't evidence it.
Follows ACoP L8 and HSG274 Part 2. Free. No spam.
Little-used showers are the worst case
The highest-risk shower on most sites is the one nobody uses. A guest en-suite, a spare changing-room shower or a rarely occupied flat leaves water standing warm in the head and hose for days or weeks, which is precisely the condition legionella needs. Descaling such a shower once a quarter is not enough on its own, because the water in between goes stagnant.
The extra control is weekly flushing. Any outlet used less than about once a week should be run regularly, typically weekly, to draw fresh water through and turn the volume over. Run it long enough to clear the standing water and bring the temperatures through, and take care to minimise spray while you do it, for example by running the head into the tray at low flow or using a bag over the rose. Our guide on how long to run taps and showers when flushing covers the timing and the aerosol precautions. The genuinely honest answer, though, is that if a shower is never going to be used, the best control is to remove it, because a dead outlet you keep flushing is a chore you will eventually forget. There is more on the outlet itself in our page on legionella in shower heads.
Where this sits in the guidance
Cleaning and descaling shower heads is one of the routine control measures set out in HSG274 Part 2, which supports the duties in ACOP L8 under the Health and Safety at Work Act. None of this cleaning makes a system "safe" by itself. It is one recurring task within a wider written scheme that also covers temperatures, monitoring and record-keeping. What earns you credit at an audit is not a spotless head on the day, but a documented frequency, a defined method and a run of dated entries showing the work has been done every time. Record each clean, keep the interval under review, and check it against your temperature records so the routine matches the risk you actually have.
Free legionella risk assessment template
A structured Word document following the five-step approach in ACOP L8. Covers risk identification, written scheme, monitoring, and records. If it isn't written down, you can't evidence it.
Follows ACoP L8 and HSG274 Part 2. Free. No spam.
Frequently asked questions
How often should shower heads be cleaned for legionella?
A common starting point, set out in HSG274 Part 2, is to dismantle, clean and descale shower heads and hoses roughly every three months. That quarterly figure is a default rather than a fixed legal limit, so your risk assessment can shorten it where water is hard, heads scale quickly or users are more vulnerable, or lengthen it where the evidence supports doing so.
Whatever interval you set, record it in the written scheme and log each clean with the date and the outlet, so you can show the task is being carried out and not just planned.
How do you disinfect a shower head?
Remove the head and hose, then descale them first so limescale and debris are gone, because scale shelters biofilm and shields bacteria from the disinfectant. Immerse both parts fully in a suitable disinfectant so every internal surface is covered, and leave them for the full contact time the product specifies.
Then rinse the head and hose with clean water to clear the disinfectant and refit them. Immersion matters because it reaches inside the hose and the back of the rose, which spraying or wiping cannot.
Why are showers a legionella risk?
Showers break water into a fine aerosol of tiny droplets that stay airborne and are easily inhaled, and breathing in contaminated droplets is the main route by which legionella reaches the lungs. That makes any spray-producing outlet a priority for control.
On top of that, the head and hose stay warm and wet between uses and clog with scale, giving conditions in the roughly 20°C to 45°C growth range where legionella multiplies. The combination of aerosol production and a warm, scaled, biofilm-friendly outlet is why showers get singled out in the guidance.
Should you descale a shower hose?
Yes. The flexible hose is often the dirtiest part of the shower and the one most commonly overlooked. It holds standing water after every use, and its ribbed inner surface is ideal for the biofilm where legionella lives, so a clean head on a fouled hose is still a risk.
Treat the hose the same as the head: remove it, descale it, immerse it in disinfectant for the full contact time, rinse and refit. If a hose is split, perished or heavily fouled, replace it rather than trying to clean it.
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