If a tap, shower or water outlet has not been used for a while, the safest answer is usually simple: run it long enough to replace stagnant water with fresh water. For many domestic outlets, this is commonly around two minutes. For little-used outlets, longer pipe runs, stored water systems or properties that have been empty, flushing may need to be closer to five minutes or until the water temperature stabilises.
Legionella flushing is not just about turning on a tap and walking away. It is a practical control measure that should be linked to a legionella risk assessment, especially for landlords, letting agents, duty holders and businesses. The aim is to reduce stagnation, manage water temperature and limit the conditions that allow Legionella bacteria to multiply.
What Is Legionella Flushing?
Legionella flushing means running taps, showers and other water outlets to move old water out of the pipework and replace it with fresh incoming water. It is most important for outlets that are rarely used, such as guest bathrooms, vacant rental properties, staff showers, external taps and rooms that have been closed for a period of time.
Legionella bacteria can grow in water systems where conditions are suitable, especially when water is stagnant and temperatures sit within the risk range. Flushing helps because it:
- Replaces stagnant water in pipework and outlets
• Helps hot water reach the correct operating temperature
• Helps cold water pull through from the incoming supply
• Reduces the time water sits unused in little-used pipework
• Supports a written control scheme for higher-risk premises
Flushing is not a replacement for proper maintenance, temperature checks, cleaning or a professional legionella risk assessment. It is one part of a wider water hygiene routine.
Ensure your property remains compliant by booking a professional legionella risk assessment today
How Long Should You Run Taps for Legionella Flushing?
As a practical guide, run most little-used domestic taps for at least two minutes, or until the water temperature clearly changes and stabilises. Where the outlet is rarely used, connected to a longer pipe run, or part of a building that has been vacant, five minutes is often a more suitable flushing period.
For cold taps, run the water until it is genuinely cold and steady. For hot taps, run the water until it becomes hot and stable. The temperature change matters because it shows that water has moved through the pipework rather than only clearing the water sitting at the outlet.
A simple rule is:
- Run regularly used taps as normal.
- Run little-used taps weekly for at least two minutes.
- Run outlets in vacant or reopened properties for around five minutes, or until temperatures stabilise.
- Flush showers carefully with the shower head lowered to reduce spray.
- Record flushing where you have formal duty holder responsibilities.
For landlords and domestic rental properties, the right flushing time depends on the property layout and the findings of the risk assessment. A small flat with mains-fed water may need a shorter flush than a large property with storage tanks, long pipe runs or rooms that are rarely occupied.
How Often Should Taps Be Flushed?
Little-used outlets should usually be flushed at least weekly. This is particularly important where a tap, shower or water outlet has not been used for seven days or more. In rental properties, landlords and agents should pay special attention to void periods, student lets, holiday lets and properties awaiting new tenants.
A good weekly flushing routine should include:
- Hot and cold taps in unused bathrooms
• Showers, including ensuite and guest showers
• Utility room sinks and cleaners’ sinks
• External taps and hose points, where safe to do so
• Any outlet that is not part of normal daily use
For commercial premises, the flushing frequency should be set by the risk assessment. Offices, salons, workshops, healthcare settings, hospitality premises and managed buildings may all have different levels of risk depending on water system design, users, occupancy patterns and stored water arrangements.
Need clarity on flushing times? Get a bespoke assessment for your specific property layout
How to Flush Taps and Showers Safely
Flushing should be done in a way that reduces exposure to water droplets. Legionnaires’ disease is linked to inhaling contaminated water droplets, so the method matters as much as the timing.
Use this basic process:
- Start gently. Turn the tap on slowly to reduce splashing, then increase the flow.
- Stand back. Avoid leaning directly over the outlet while the water first runs.
- Flush cold first, then hot. This helps you check whether temperatures are changing correctly.
- Keep shower heads low. Place the shower head near the drain or bath base to reduce aerosol spray.
- Record the task. In managed properties, note the date, outlet and person responsible.
Do not remove scald protection or alter thermostats without competent advice. Hot water systems need to control Legionella risk, but they must also manage scalding risk, especially where vulnerable people may use the building.
Stay safe and compliant with our professional water hygiene and safety management services
When Is Flushing Most Important?
Legionella flushing is most important whenever water has had time to sit still.
After a Property Has Been Empty
If a rental property, office or commercial unit has been empty for more than a week, all outlets should be flushed before normal use resumes. In a domestic property, this often means running taps and showers for two to five minutes, with extra care for showers because they create spray.
For longer void periods, flushing alone may not be enough. The system may need a review, especially if there are cold water tanks, poor hot water temperatures, redundant pipework or visible scale on outlets.
Before a New Tenant Moves In
Landlords should make sure water outlets are safe and ready for use before a new tenancy begins. This includes checking that taps and showers run properly, hot water reaches suitable temperatures, cold water runs cold, and any unused outlets have been flushed.
A legionella risk assessment for landlords can identify whether simple controls are enough or whether further action is needed. It also gives a clear record that the property has been checked by a competent assessor.
In Businesses With Little-Used Rooms
Commercial premises often have outlets that are easy to forget. Staff showers, unused toilets, welfare rooms, treatment rooms, stores and seasonal areas can all become stagnation points. A flushing schedule should list each outlet clearly, assign responsibility and confirm how often the task must be done.
Our commercial assessments identify every hidden risk, ensuring no outlet is ever left forgotten
Does Flushing Remove Legionella Completely?
Flushing helps reduce risk, but it does not guarantee that Legionella has been removed completely. Bacteria can exist in biofilm, scale, sediment, tanks, hoses and parts of a water system that are not properly controlled. That is why flushing should sit alongside other control measures.
Important controls include:
- Keeping hot water hot enough through storage and distribution
• Keeping cold water below risk temperatures where practical
• Cleaning and descaling shower heads and hoses
• Removing redundant pipework and dead legs
• Inspecting cold water storage tanks where present
• Reviewing the legionella risk assessment when the property or usage changes
If a property has ongoing temperature problems, visible contamination, poor water turnover or a history of long vacancy periods, it is sensible to get professional advice rather than relying on flushing alone.
Should Landlords Keep Legionella Flushing Records?
For a simple domestic rental property, the legal position is usually proportionate to the risk. However, written records are useful because they show that water hygiene has been considered and managed. For businesses, duty holders and larger managed premises, records are much more important.
A basic flushing record can include:
- Property address or room location
• Outlet flushed
• Date and time
• How long the outlet was run
• Any temperature concerns
• Name of the person completing the check
• Follow-up action required
Records help letting agents, landlords and business owners prove that control measures are being completed. They also make it easier to spot recurring problems, such as a shower that is rarely used or a hot tap that never reaches a suitable temperature.
Common Mistakes With Legionella Flushing
Legionella flushing is simple, but it is often done inconsistently or without a clear routine. These common mistakes can leave stagnant water in the system, reduce the value of flushing, and make it harder to show proper water hygiene management.
Treating Flushing as a One-Off Task
Running taps once before a tenant arrives is useful, but it does not manage outlets that remain unused. Flushing should be repeated regularly where water could stagnate between periods of use.
Flushing Showers at Full Height
Showers can create fine water droplets, so flushing them at head height can increase exposure risk. Keep the shower head low, close to the drain, and run the water carefully.
Forgetting Rarely Used Outlets
External taps, guest bathrooms, utility sinks and locked rooms are easy to miss. Any outlet that is not used regularly should be included in the flushing schedule and checked consistently.
Failing to Clean Shower Heads
Scale, sediment and biofilm can build up in shower heads and hoses. Regular cleaning and descaling helps support flushing, improves water flow, and reduces conditions where bacteria may develop.
Giving Tenants Vague Instructions
If tenants need to flush an unused shower or tap, explain exactly what to do and how often. Clear written guidance helps avoid confusion and supports consistent legionella control.
Avoid common pitfalls by letting our specialists train your team in correct flushing protocols
When Should You Book a Legionella Risk Assessment?
You should book a legionella risk assessment if you are a landlord, property manager, duty holder or business owner and you are unsure whether your flushing routine is enough. An assessment looks at the water system, identifies risk factors and gives practical recommendations.
At Legionella Risk and PAT, we provide domestic and commercial legionella risk assessments across Scotland, including support for landlords, agencies, businesses and duty holders. We can assess your property, explain suitable control measures and provide clear documentation for your records.
