---
title: "How to implement a flushing programme for Legionella control"
source_url: https://legionella.io/articles/how-to-implement-a-flushing-programme-for-legionella-control/
canonical_url: https://legionella.io/articles/how-to-implement-a-flushing-programme-for-legionella-control/
pillar: "Monitoring, Flushing & Sampling"
summary: "A step-by-step UK guide to a Legionella flushing programme: which low-use outlets to list, how often to flush, the method, and the records that prove it."
primary_keyword: "Legionella flushing programme"
date_published: 2025-05-18
date_reviewed: 2026-06-26
author: "Legionella.io editorial team (REMOTE TECH LTD)"
reviewed_against: "HSE L8 and HSG274 guidance"
region: "United Kingdom"
license: "(c) REMOTE TECH LTD. Quote freely with attribution and a link to source_url."
---

# How to implement a flushing programme for Legionella control

Flushing is the cheapest control measure on your site and the one most likely to fail quietly. Not because it is technically hard — running a tap is not hard — but because it is dull, spread across dozens of outlets, and almost never recorded in a way that would survive a look from an enforcing officer.

A flushing programme is really four things: the right list of outlets, a sensible frequency for each, a method a technician can follow without guessing, and a record that proves it happened. Flushing little-used outlets to stop water sitting still is exactly the kind of control HSE expects a duty holder to have in place and to be able to demonstrate [1][3]. Get the outlet list wrong, though, and everything downstream is wasted effort. So that is where this starts.

## Before you start

You need three things in hand. A current Legionella risk assessment, because that is what tells you which outlets are low-use and what the acceptable temperatures are. An asset list or schematic so you are not working from memory. And a named person who owns the programme — not "facilities" in the abstract, an actual human who notices when a task slips.

If any of those is missing, fix that first. A flushing schedule built on guesswork about which taps get used is worse than no schedule, because it manufactures paperwork that looks like control and isn't.

## Deciding what goes on the list

The single most useful decision is also the one most programmes skip: separating the outlets that flush themselves from the ones that don't. Work each outlet on your register down this branch.

- **Does it get used at full flow about as often as your assessment expects for a "regularly used" outlet?**
  - **Yes** → normal use is already drawing fresh water through it. Note it on the register, but it does not need a dedicated flush task.
  - **No** → it is a low-use outlet. Keep going.
- **Is the outlet genuinely needed?**
  - **No** → don't sentence yourself to flushing it forever. Remove the fitting and the pipework back to the live main so there is nothing left to stagnate [3].
  - **Yes** → it goes on the flushing schedule. Set its frequency from the risk assessment, and weight it upward if it produces a spray or serves people who are more vulnerable to infection.

That last branch is the heart of it. The shower in a disabled toilet that gets booked twice a term, the cleaner's sink on a top floor, the tap in the plant room, the emergency deluge shower — these are the outlets that turn warm, still water into something a person breathes in. Inhalation of contaminated aerosol is how the disease is caught in the first place [5], so the aerosol-producing low-use outlet is your priority, not the busy basin by the front door.

## Building the programme, step by step

### 1. Write the outlet register

Walk the building with the risk assessment, not from the office. For each low-use outlet, record where it is, whether it is hot or cold (or both), and an honest estimate of how often it actually gets run. You are done when each line on the register would let someone who has never been to the site find the outlet and know why it is listed.

### 2. Set a frequency per outlet

Resist one blanket number. A common starting point is to run little-used outlets at least weekly [2], but the risk assessment sets the actual figure based on temperature, exposure and use pattern. A spray outlet serving vulnerable users may warrant more; a cold-only tap that already runs near mains temperature may warrant less. The test of a good schedule is that every frequency has a reason attached to it, not just a tick-box interval.

### 3. Write the method down

This is where generic advice stops and a real programme begins. The method must say: run both the hot and the cold, run until the temperature stabilises — hot up to its operating temperature, cold down towards its incoming temperature [3] — and run long enough to pull fresh water through the whole branch, not just clear the tap body. (For what those hot-side targets actually are, see [Hot water temperature guidelines](https://legionella.io/articles/hot-water-temperature-guidelines-to-prevent-legionella/).)

Then the part most guides leave out. The whole reason you are flushing this outlet is that it is the one most likely to throw a fine mist, so flush it in a way that limits the spray you create while doing it [2]. Take the shower head off and run into the tray, or run at low flow, or do it while the room is empty. Two technicians given this method should flush the same outlet the same way.

### 4. Assign it and put it on a calendar

A programme without an owner is a wish. Each task needs a named person and a due date, and someone has to notice when it goes overdue. Where you can, tie flushing to how the building is actually used — a room or wing coming back into service after standing empty gets flushed before anyone uses it, not on the next routine sweep.

### 5. Record the flush, and record the miss

Log the date, the outlet, the temperature it reached, and who did it. The records that matter most are the exceptions: the flush that got missed, the outlet that never reaches temperature, the spray tap that came back discoloured. A flush log that is wall-to-wall ticks with no exceptions usually means nobody is reading the thermometer. Keep these alongside your other compliance records — [Essential records for Legionella compliance](https://legionella.io/articles/essential-records-for-legionella-compliance/) covers what the wider file should hold.

### 6. Review and prune

The best flush is the one you no longer have to do. At each review, ask which outlets on the schedule are still genuinely needed. Capping and removing redundant pipework retires the risk permanently, whereas flushing a dead leg manages it forever and depends on nobody ever forgetting [3]. A shrinking schedule is usually a sign the programme is working, not slacking.

## A note on the numbers

The frequencies, run times and temperatures above are orientation, not figures to lift straight onto a clipboard — including from here. They come from a competent, site-specific risk assessment that has looked at your pipework, your users and your actual readings. Treat a number like "weekly" as the shape of the answer and let the assessment set the real value for your building. Flushing is also only one control among temperature management, cleaning and disinfection; a tidy flush log does not on its own prove the water is safe.

Your first move this week is not to write a policy. It is to walk the building with the risk assessment in hand and mark, outlet by outlet, which taps and showers nobody actually uses. That marked-up list is your flushing programme in embryo — everything above is how you turn it into something that holds.

## Common questions

### How long should we run an outlet to count it as flushed?
Run it until the temperature stabilises — hot up to its operating temperature, cold down towards its incoming temperature — and until enough water has passed to replace the standing water in that branch [3]. Time on its own is a poor proxy: a long dead leg needs far longer than a tap hanging off a live riser. Set the duration per outlet and confirm it against your risk assessment.

### There's a shower no one has used in months — keep flushing it or rip it out?
If it is genuinely redundant, removing the fitting and the pipework back to the live main beats flushing it indefinitely, because a dead leg you have deleted cannot stagnate [3]. If it might be needed again, keep it on the schedule. What you should not do is cap it and walk away — a capped spur still connected to the live system is exactly the dead leg you were trying to avoid.

### Does a clean flushing log mean we can skip temperature monitoring or sampling?
No, because they answer different questions. Flushing is a control; temperature monitoring verifies the control regime is working; sampling is occasional verification when the assessment calls for it, and its frequency follows the system and the risk assessment rather than a fixed calendar [4]. A perfect flush record with no temperatures tells you the tap ran, not that the water was safe. See [Legionella sampling 101](https://legionella.io/articles/legionella-sampling-101-how-and-why-to-test-your-water/) for where testing fits.

## Related reading

- [Routine monitoring and flushing: the basics](https://legionella.io/articles/routine-monitoring-and-flushing-the-basics/)
- [Hot water temperature guidelines to prevent Legionella](https://legionella.io/articles/hot-water-temperature-guidelines-to-prevent-legionella/)
- [Essential records for Legionella compliance](https://legionella.io/articles/essential-records-for-legionella-compliance/)
- [Legionella sampling 101: how and why to test your water](https://legionella.io/articles/legionella-sampling-101-how-and-why-to-test-your-water/)

## Sources

[1] HSE, "Legionnaires' disease. The control of legionella bacteria in water systems - Approved Code of Practice and guidance (L8)". https://www.hse.gov.uk/pubns/books/l8.htm
[2] HSE, "Legionnaires' disease: Technical guidance (HSG274)". https://www.hse.gov.uk/pubns/books/hsg274.htm
[3] HSE, "Hot and cold water systems". https://www.hse.gov.uk/legionnaires/hot-and-cold.htm
[4] HSE, "Testing and monitoring your water system for legionella". https://www.hse.gov.uk/legionnaires/testing-monitoring-water-system.htm
[5] CDC, "How Legionella Spreads". https://www.cdc.gov/legionella/causes/index.html