A bank of changing-room showers is one of the more efficient aerosol generators a building owns: a row of heads that warm water passes through, broken into a fine mist at head height, with a person standing in it. Add the use pattern a gym or leisure centre actually has, slammed at 6pm, idle at 2pm, some heads barely touched for weeks, and you have the two ingredients Legionella needs, warm water and time sitting still.
This is not a reason to fear the showers. It is a reason to give them a routine, because in a leisure setting they, not the pool, are usually the outlet that matters most.
Why the showers, not the pool
The water people worry about in a leisure centre is the pool. The water most likely to carry Legionella into a pair of lungs is the shower. Legionnaires’ disease is contracted by breathing in small droplets of contaminated water that travel deep into the lungs; it is not passed person to person, and you do not get it from swallowing water [5][1]. A shower head is built to make exactly that mist, warm, fine, and right in the breathing zone.
Pool water itself is continuously treated and circulated, which is a different control problem. The systems that throw a breathable aerosol are the ones HSE flags as most likely to create a Legionella risk, and in the dry side of a leisure building that means the showers above all [1]. The wet-side plant has its own higher-risk member, the spa pool, which sits under separate guidance, HSG282, and is covered in Safe operation of spa pools and hot tubs under HSG282 [6].
What makes leisure showers different from the one at home
Three things set a leisure shower block apart from a domestic bathroom.
First, scale. Dozens of heads, some that the public favour and some at the far end of a row that almost nobody reaches, so flow is wildly uneven across outlets that share the same pipework.
Second, lumpy demand. A leisure centre runs in surges, a swim session, a class, a school visit, that hammer a handful of heads and leave the rest unused in between. Cold water meant to stay below 20°C and hot water meant to stay genuinely hot both drift toward the 20–45°C band where the bacteria multiply most readily, especially in branches that see little flow [2].
Third, the calendar. School holidays, term breaks, a wing closed for refurbishment, a 6am-to-10pm timetable that leaves the building dead overnight. Each is a stretch in which outlets stagnate and then get used again with no deliberate flush.
Warm, humid changing rooms finish the picture. The broader water-safety and budget view for a sports and fitness site is in Legionella considerations in sports and fitness centres; this is the shower-specific slice of it.
The control routine that fits a leisure site
This is the payload, a proportionate routine you can run and record. The frequencies come from your risk assessment; the actions stay constant.
Temperature
- Check that hot water reaches the showers hot and cold stays cold, at sentinel and representative outlets, on the schedule your assessment sets [2].
- Treat blended and TMV-fed showers as warm reservoirs: the blended water sits in the growth band, so the valves need servicing and the outlets need flushing [2].
Flushing the heads demand misses
- Identify every shower that surges of use do not reach, the far end of the row, the accessible cubicle, the staff shower, the second changing village used only for galas.
- Flush them on a defined frequency, running each long enough to draw through fresh water and clear what was standing [1].
- Recommission deliberately after any closure, holidays, a quiet spell, a refurbished wing, rather than letting the first member through the door be the flush.
Heads, hoses and fittings
- Clean and descale shower heads and flexible hoses on a set schedule; scale and biofilm shelter bacteria and break up the spray, and the detail is in Showerhead cleaning and descaling schedules.
- Replace perished hoses and heads that no longer drain, a hose that holds water between uses is a small warm reservoir of its own.
Records
- Date and sign every temperature check, flush and descale, so an outlet that quietly lapses shows up before an inspector or an illness does [4].
The heads everyone forgets
A few outlets get missed almost every time. The accessible shower nobody uses for a fortnight. The poolside rinse shower that runs all summer and never in winter. The staff shower behind the office. The “spare” changing village kept for busy weekends. Low use reads as low risk, when it is the opposite: stagnation grows the bacteria, footfall does not. Those forgotten heads belong on the flushing schedule first, not last.
A fair caveat
This is general guidance on where the risk sits in a leisure setting, not a control scheme for your building and not legal advice. What goes on the assessment, which outlets are sentinels, how often each is flushed or descaled, and whether sampling is warranted are decisions for a competent person working from a current, site-specific risk assessment under ACoP L8 [3][4]. A hydrotherapy pool, or a centre serving frail or immunocompromised users, carries heavier risk than a members’ gym, and the scheme should say so. Spa pools and hot tubs run under their own guidance, HSG282 [6], and public pools and splash features have their own considerations in Controlling Legionella in public pools and water parks.
Your next step this week
Walk both changing rooms at a quiet hour with a clipboard and mark every shower head. For each, answer three things: when did water last run through it, is it on a flushing or descaling schedule, and who signs that off. The far end of a row and the accessible cubicle are usually where the blanks are. Then give those recurring flushes and descales a dated home rather than a memory, so the head nobody uses does not become the one nobody checks.
Common questions
Can you catch Legionnaires’ disease from a gym shower?
It is possible but uncommon. The risk arises when water has sat warm and still long enough for Legionella to multiply and a shower head then turns it into a breathable mist [1][5]. A busy head fed with properly hot or properly cold water is lower risk than one that is rarely used or fed by a neglected blending valve. Flushing little-used heads and keeping the temperatures right is what holds the risk down.
How often should leisure-centre showers be flushed and descaled?
There is no single number to copy: the frequency is set by your site’s risk assessment for each outlet, based on how much it is used and the temperatures it runs at [3]. Little-used heads are flushed on a regular defined schedule rather than left between surges of demand, and heads and hoses are cleaned and descaled often enough to keep scale and biofilm in check [1]. The point is that it is scheduled and recorded, not done from memory.
Are swimming pool showers higher risk than the pool itself?
For the inhalation route, usually yes. Pool water is continuously treated and circulated, whereas a shower turns warm water into a fine aerosol right at face height, which is the recognised exposure route for Legionnaires’ disease [1][5]. The pool has its own water-safety considerations, and the spa pool is a separate higher-risk system under HSG282 [6], but among the dry-side outlets, the showers deserve the closest attention.
Sources
- HSE, “Systems most likely to create legionella risk”. https://www.hse.gov.uk/legionnaires/risk-systems.htm
- HSE, “Hot and cold water systems”. https://www.hse.gov.uk/legionnaires/hot-and-cold.htm
- HSE, ACoP L8 (2013), “Carrying out a risk assessment”, p.12. https://www.hse.gov.uk/pubns/books/l8.htm
- HSE, “Legionnaires’ disease, what you must do”. https://www.hse.gov.uk/legionnaires/what-you-must-do/index.htm
- CDC, “How Legionella Spreads”. https://www.cdc.gov/legionella/causes/index.html
- HSE, “Control of legionella and other infectious agents in spa-pool systems (HSG282)”. https://www.hse.gov.uk/pubns/books/hsg282.htm