Short answer: HSE's HSG274 Part 2 says any outlet not used for seven days or more goes on a flushing regime: run it weekly until the temperature stabilises and is comparable to the supply, and log it. Once started, flushing "has to be sustained and logged" (para 2.78). Healthcare and care homes may need it more often. Site staff usually do it, because it falls between contractor visits.
The weekly rule
Water standing in little-used taps, showers and dead legs is where HSE expects trouble. HSG274 Part 2 says: "When outlets are not in regular use, weekly flushing of these devices for several minutes can significantly reduce the risk of legionella proliferation in the system. Once started, this procedure has to be sustained and logged, as lapses can result in a critical increase in legionella at the outlet" (para 2.78).
| What | Action |
|---|---|
| Which outlets | Equipment "not used for a period equal to or greater than seven days" goes on the flushing regime |
| How | Flush the outlets until the temperature at the outlet stabilises and is comparable to the supply water, and purge to drain |
| Keeping it going | Sustain and log the procedure once started |
| High-risk populations | Healthcare and care homes: more frequent flushing may be needed, as the risk assessment indicates |
| Better still | Consider removing infrequently used showers, taps and equipment, and cut the supply pipe back to a common supply, preferably by removing the feeding tee |
| Frequency | Weekly, or as indicated by the risk assessment |
Other weekly and more frequent rules in the same guidance
- Healthcare with susceptible patients: where outlets are not in regular use, "the risk assessment may indicate the need for more frequent flushing, ie twice weekly", and water draw-off should be part of the daily cleaning (para 2.166).
- Empty homes: "outlets on hot and cold water systems should be used at least once a week to maintain a degree of water flow" (para 2.144). For longer gaps, consider a flushing regime or draining the system.
- Standby pumps: "should be used at least once each week to avoid water stagnation" (para 2.61).
- After a lapse: if flushing has been missed, the stagnant water in the shower or tap and its dead leg "should be purged to drain without discharge of aerosols before the appliance is used" (para 2.167).
How to flush an outlet
- Work from the site's list of little-used outlets, not from memory.
- Keep spray down. HSE's web guidance says to "flush through and purge to drain, without release of aerosols". Follow the method in the written scheme.
- Run hot and cold until the temperature at the outlet stabilises and is comparable to the supply (Table 2.1). HSE describes this as running for "several minutes" (para 2.78).
- Sign the log: outlet, date, time run, initials.
Worked example: an office with three quiet outlets
The risk assessment lists three outlets used less than once a week: a basin in a fourth-floor meeting suite, a cleaner's sink in the basement, and the shower in an accessible changing room.
- Every week: the caretaker flushes all three on Monday morning and signs the sheet kept in the cleaner's cupboard. A named deputy covers holidays.
- Every month: the maintenance contractor takes the sentinel temperatures, checks the flushing sheet for the past four weeks and reports any missed week to the responsible person in writing.
- After the Christmas closure: the building was shut for 11 days. Every outlet has gone at least seven days unused, so all of them are flushed, without spray, before people return. For a longer closure, the risk assessment should set the plan for reopening.
- At the next review: the assessor is asked whether the meeting-suite basin can be removed and its pipe cut back (Table 2.1 and para 2.77).
Who does what
- The dutyholder owns the risk assessment and the written scheme, which should set out the precautions, such as flushing, and the checks and their frequency (L8, paras 28 and 60).
- The responsible person makes sure the flushing happens and covers absences. L8 asks for responsibilities to be "well defined in writing and understood by all concerned", including outside companies (para 56).
- Site staff (caretakers, cleaners, housekeeping) usually do the flushing. They need suitable information, instruction and training (L8, para 52).
- The maintenance contractor checks the log on each visit, reports gaps and outlets that should be removed, and does the flushing only where the contract says so.
What to record, and for how long
- The list of outlets on the regime, with references matching the schematic
- For each flush: outlet, date, time run or temperature reached, initials
- Missed weeks, why, and the purge done before the outlet was used again
- Outlets removed, and the date the regime for them stopped
L8 says records of any monitoring, inspection, test or check, with the dates, are kept "for at least five years" (para 72).
Flushing and Field Suite
Field Suite does not schedule weekly tasks. Contract visits are set in whole months, so the weekly flushing log stays with the site. What fits is the check on it:
- Build your own temperature log in the form builder for the monthly visit, and add a yes/no question: "Site flushing log complete for every week since the last visit". Mark "No" as a fail answer, so a missed week fails the form and alerts the office.
- Found on the visit: outlets that should be removed, or a log that has stopped, go in as faults marked by urgency, print on the job sheet and can be turned into a quote.
- Contracts: a visit that repeats every month creates the job to book a set number of days before it is due, with the form ready on the engineer's phone.
See planned maintenance software or book a demo. Read Legionella checks for hot and cold water systems for the full checklist, and use the monthly temperature log template.
Questions
Does the weekly rule apply to every outlet?
No, only to outlets and equipment not used for seven days or more. Outlets in regular use keep the water moving by themselves.
How long should an outlet be flushed?
Until the temperature at the outlet stabilises and is comparable to the supply water (Table 2.1). HSE also describes it as "several minutes" (para 2.78). The written scheme may set a time.
Can we stop flushing once we start?
HSE says that once started, the procedure "has to be sustained and logged", because lapses can cause "a critical increase in legionella at the outlet" (para 2.78). Removing the outlet and cutting the pipe back is the way to end it.
Does the contractor have to do the flushing?
Not unless the contract says so. The written scheme says who does it. Most often it is site staff, with the contractor checking the log.
Field Suite is job management software, not a water hygiene consultancy. The building's own risk assessment and written scheme decide which outlets are flushed, how and how often.
Sources
- HSE, Legionnaires' disease: Technical guidance, HSG274 Part 2 (second edition, 2024), paras 2.61, 2.77, 2.78, 2.144, 2.166, 2.167 and Table 2.1. https://www.hse.gov.uk/pubns/priced/hsg274part2.pdf
- HSE, L8 Approved Code of Practice and guidance (fourth edition, 2013), paras 28, 52, 56, 60 and 72. https://www.hse.gov.uk/pubns/priced/l8.pdf
- HSE, Hot and cold water systems: things to consider. https://www.hse.gov.uk/legionnaires/things-to-consider.htm
Last checked: 5 November 2026 against the sources above.
Field Suite is job management software for UK building services firms, not a consultancy. Your own risk assessments, contracts and advisers decide what applies to your work. Spotted a mistake? Email info@fieldsuiteapp.com and we correct it.