How often should taps be flushed for legionella?
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Key points
- The rule is weekly for little-used outlets — any tap drawn off less than about once a week.
- Taps in normal use need no flushing: daily use already provides the turnover. Flushing frequency follows usage, not a blanket building-wide rule.
- Flush to temperature, not to the clock: hot stabilising at 50°C or above, cold below 20°C.
- Open the outlet gently to limit aerosol — flushing a colonised tap releases spray.
- Record every flush: date, outlet, temperature, initials. Kept five years or more, the log is the proof the control happened.
Taps that are used less than about once a week should be flushed weekly — run until the temperature stabilises, hot water reaching at least 50°C and cold dropping below 20°C, and the flush recorded. Taps in everyday use do not need flushing at all: regular use is already doing the job. The frequency is set by how often each individual outlet is used, not by a blanket timetable applied to the whole building.
Usage sets the schedule
This is the point most flushing advice misses. The purpose of flushing is to replace the water turnover that normal use would have provided, so the question is never "how often should taps be flushed" but "which of my taps are not flushing themselves". Walk the system outlet by outlet and ask how often each is genuinely drawn. Anything honestly used several times a week comes off the list. Anything below about one use a week — the guest bathroom, the cleaner's sink, the outside tap, the washroom on the closed floor, the tap left live on a branch after a fixture was removed — goes on the weekly regime. Identifying these overlaps heavily with finding dead legs: a little-used tap is effectively a live dead leg.
How a weekly flush is done
Open the outlet gently — a tap or shower that has stood for a week may be colonised, and opening it fully atomises the water into the aerosol that carries legionella. Run the hot side until it reaches at least 50°C (55°C in healthcare) and the cold side until it drops below 20°C, then stop: the stabilised temperature is the proof the branch has turned over, which is why flushing "for two minutes" is the wrong habit — a distant outlet on a long branch takes longer, a near one less. On spray fittings and showers, remove the head and run a plain stream where you can. The full method, including flushing after closures and voids, is in flushing little-used outlets, and how long to run taps works through the timing question in detail. The temperature checker makes the to-temperature check a two-minute job per outlet.
Flushing frequency follows usage. A tap in daily use flushes itself; the tap nobody uses is the one that needs a weekly, recorded run through to temperature.
When weekly is not enough — or not needed
Weekly is the baseline for little-used outlets, but the risk assessment can tighten or replace it. Higher-risk settings, or outlets serving susceptible people, may be flushed more often. A building that will stand empty for a defined short period can be kept on a weekly whole-system flush instead of facing a full recommissioning at the end. And an outlet that will never be used again should not be flushed forever — it should be removed back to the live pipe, because a removed outlet is a control that cannot be forgotten. After a long closure with no interim flushing, weekly flushing is no longer the right tool at all: the whole system needs flushing through to temperature, and possibly disinfection before reoccupation.
The flush that was not written down
Whatever the frequency, the flush only counts if it is recorded: date, outlet, who did it, and the temperature reached, kept in the log book for at least five years. The flushing list and frequency belong in the written scheme of control that follows the risk assessment, so the outlet identified as little-used, the weekly task, and the log entry all join up. An unrecorded flush, done faithfully every week, cannot be evidenced — and on paper, a control that cannot be evidenced did not happen.
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.
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 taps be flushed for legionella?
Any tap used less than about once a week should be flushed weekly: run it until the temperature stabilises, hot reaching at least 50°C and cold dropping below 20°C, and record the flush. Taps in normal regular use need no flushing at all, because ordinary use is already turning the water over. The frequency follows the usage of each outlet, not a blanket rule for the whole building.
Do taps in regular use need flushing?
No. Flushing exists to replace the turnover that normal use would have provided, so a kitchen tap or busy washroom basin used every day is already flushing itself. Flushing these outlets wastes water and adds records without adding control. The outlets that belong on the regime are the ones whose use has dropped below roughly once a week — guest rooms, cleaners' cupboards, outside taps, little-used washrooms and any tap left on a branch after a fixture was removed.
How long should each tap be run when flushing?
Run until the temperature at the tap stabilises, not for a fixed number of minutes. Hot water should reach at least 50°C (55°C in healthcare), cold should fall below 20°C. A tap on a long branch takes longer to turn over than one near the riser, so a single guessed time cannot be right for every outlet — the stabilised temperature is the proof that fresh water has arrived.
What should you record when flushing taps?
Record the date, the outlet, who carried out the flush and the temperature the water stabilised at, hot and cold. Note anything unusual — discoloured water, an outlet that will not reach temperature — and the action taken. The record is the evidence the control happened, so an unrecorded flush counts for nothing if an inspector, insurer or court later asks how the outlet was managed. Records are kept for at least five years.
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