Water that sits still in pipes, taps and showers can warm up and stagnate. That is exactly the kind of condition in which Legionella bacteria can grow. Flushing little-used outlets is one of the simplest and most effective ways to keep water moving, and it is usually one of the first actions a Legionella risk assessment will recommend. This guide explains what to flush, how often, and what to record.
Why stagnant water is a problem
Legionella bacteria grow in water between roughly 20°C and 45°C, and are controlled by keeping cold water cold, hot water hot and water moving. Irish guidance, including the Health Protection Surveillance Centre’s national guidelines and the Health and Safety Authority’s risk assessment templates, points to temperature control (hot water stored above 60°C and distributed above 50°C, cold water below 20°C), regular flushing of infrequently used outlets, and regular cleaning of shower heads and tanks. Treat these as published guidance, and always follow the specific figures in your own written risk assessment.
Which outlets count as “little used”?
Any tap, shower or other water outlet that is not used regularly, typically at least weekly. Common examples include:
- Showers and basins in empty or seasonal rooms, guest rooms and holiday lets
- Staff showers, changing rooms and sports facilities
- Outlets in meeting rooms, disused kitchens and spare toilets
- Outside taps, hose connections and cleaners’ sinks
- Outlets in premises that close for holidays, weekends or part of the year
See our guides for part-time premises, clubs, halls and holiday lets and the Legionella records to keep.
How to flush safely
- Follow your risk assessment. It should list which outlets need flushing, how often and for how long.
- Flush at least weekly. Both hot and cold taps, and showers, should be run regularly. After a holiday or longer closure, flush before the premises reopens.
- Keep spray to a minimum. Run taps gently and, for showers, remove the head or direct the flow safely to the drain to avoid creating a fine mist that could be breathed in.
- Check temperatures. Cold water should run cool and hot water should reach temperature at the outlet. Report anything that does not.
- Record it. Note the date, the outlet, who flushed it and any problems found.
Who should do it?
A named, trained person such as a caretaker, maintenance lead or manager should be responsible, with a deputy for holidays and sickness. The duty holder remains responsible for making sure it happens. A flushing log that is filled in consistently is good evidence that your controls are working.
Beyond flushing: shower heads and tanks
Shower heads and hoses can collect scale and biofilm, so they should be cleaned and descaled regularly. HSA school templates suggest quarterly cleaning and disinfection, with storage tanks checked and cleaned. Read about shower head disinfection and Legionella testing and sampling.
When should you get a professional involved?
- You do not have a current written Legionella risk assessment
- Outlets are rarely used and you are unsure of the right regime
- Temperatures are not reaching the figures in your assessment
- You have had a change of use, refurbishment or a long closure
We carry out Legionella risk assessments, sampling, tank cleaning and shower head disinfection across Ireland. Read about our Legionella risk assessments or contact us for a free written quote. We assess first so the quote matches your actual system.
This article is general guidance and is not a substitute for a site-specific risk assessment. Follow the instructions in your own assessment.