Legionella Checks for Landlords: What You Need to Do and When

As a landlord in the UK, you have a legal duty to manage legionella risk in the water systems of properties you let. HSE's guidance for landlords confirms that compliance does not need to be costly or complicated for most residential properties — but it does require specific checks carried out at specific intervals.

This guide covers what checks you need to do, how often, and what records you should keep.

Before you let the property

These checks happen before a new tenancy begins, and after any period of vacancy.

1. Flush the water system

HSE requires "flushing out the system prior to letting the property." This means running all hot and cold outlets for several minutes before the tenant moves in. After any extended vacancy (two weeks or more), run all taps, showers, and toilets until the water temperature stabilises.

For a property that has been empty for several months, a thorough flush takes 15–30 minutes and covers every outlet including garden taps, utility sinks, and infrequently used bathrooms.

2. Check the hot water cylinder temperature

The hot water cylinder (if your property has one rather than a combi boiler) must store water at 60°C or above. HSE specifies "setting control parameters (such as setting the temperature of the hot water cylinder to ensure water is stored at 60°C)." Check the thermostat dial before each new tenancy and verify with a thermometer at the nearest hot outlet.

3. Remove any dead legs

HSE guidance states that landlords should "make sure any redundant pipework identified is removed." A dead leg is any capped or disconnected section of pipe — from a removed sink, moved bathroom, or old extension — where water sits stagnant. If you cannot remove a dead leg before letting, it must be identified in the risk assessment and flushed regularly.

4. Inspect cold water storage tanks (if present)

Many modern properties draw cold water directly from the mains and have no cold water tank. If your property has a storage tank (often in the loft), inspect it before letting:

Lid fits tightly with no gaps
Tank is insulated against heat gain
No visible debris, algae, or discolouration
Overflow pipe is screened to keep insects out

HSE notes that if the cold water supply is "directly from a wholesome mains supply (no stored water tanks)" the risk is substantially lower.

5. Complete or review the risk assessment

A legionella risk assessment must be completed before the property is let, and reviewed before each new tenancy or whenever anything changes. For a standard property, a landlord can do this themselves. See our guide to legionella risk assessments for landlords for what the assessment must cover.

During the tenancy

These are the ongoing monitoring duties while the property is occupied.

Monthly: temperature checks at sentinel outlets

Each month, run the hot tap at the outlet nearest to the hot water cylinder until the temperature stabilises, then measure it. Also run the cold tap at the furthest point from the mains entry until temperature stabilises and measure. Record the date, outlet location, and reading.

The targets are:

Hot water at outlets: 50°C or above within one minute of running
Cold water at outlets: below 20°C within two minutes of running

If a reading misses these targets, investigate the cause promptly and note the corrective action.

Weekly: flush infrequently used outlets

Any outlet that has not been used in the past seven days needs to be flushed. Run hot and cold for at least two minutes. This is most relevant for guest bathrooms, utility room taps, and en-suites that tenants rarely use.

For a single-let property with one bathroom, the tenant's normal daily use usually covers this. For an HMO with multiple bathrooms, ensure there is a system in place so every outlet is used or flushed weekly.

Quarterly: clean and descale showerheads

Showerheads accumulate scale and biofilm and create fine aerosols — which is why showers are the primary route of legionella inhalation. Every three months, remove showerheads and flexible hoses, soak in descaler or dilute bleach, rinse, and reinstall. HSE guidance specifically notes that "tenants should regularly clean and disinfect showerheads."

As a landlord, you are responsible for ensuring this happens. Either carry it out yourself at inspection visits, or communicate the requirement clearly to tenants and record when it was last done.

As needed: respond to system changes

If any of the following occur, review or update the risk assessment and carry out the appropriate checks:

Trigger	Action
New tenancy	Pre-let flush, temperature check, risk assessment review
Renovation or plumbing work	Check for new dead legs, recheck temperatures
Heating system failure or repair	Temperature check after repair
Extended void (2+ weeks)	Flush all outlets on re-occupation
Tenant reports temperature problems	Investigate immediately, document findings

What records to keep

HSE notes that while records are not legally mandatory for all residential landlords, "you may find it wise to keep a record of what has been done." In practice, records are the only evidence that checks were completed. If a tenant were to become unwell and a claim arose, records showing consistent monitoring are your primary defence.

At minimum, keep:

The risk assessment — property address, system description, hazards identified, control measures, review date, named responsible person
Monthly temperature readings — date, outlet location, temperature recorded
Quarterly showerhead maintenance log — date, which showerheads cleaned
Pre-let flush log — date, tenancy changeover, who carried out the flush
Any remedial actions — what failed, what you did, when

A simple spreadsheet or paper log book works. For multiple properties, a system that tracks which checks are overdue across the portfolio becomes important — one of the things LegioLog is building for landlords. Join the waitlist to be notified when it launches.

What you do NOT need to do

HSE is clear on this. For a standard domestic hot and cold water system in a residential let:

You do not need to test the water for legionella bacteria. HSE states that microbiological testing "is not usually required for domestic hot and cold water systems." Testing is needed for high-risk systems (cooling towers, hospital water, etc.) not for ordinary residential properties.
You do not need to hire a professional accredited assessor. Most landlords can self-assess competently.
You do not need a legionella certificate. There is no legal requirement for a formal certificate for a domestic property. See our guide on what a legionella certificate actually is.

Summary checklist

Frequency	Check	Record
Before each let	Flush all outlets	Date, outlets covered
Before each let	Check cylinder temperature	Date, temperature
Before each let	Review risk assessment	Updated document
Monthly	Hot + cold temperature at sentinel outlets	Date, outlet, reading
Weekly	Flush unused outlets	Date, outlet
Quarterly	Clean + descale showerheads	Date, which showerheads
After any system change	Review and recheck as relevant	Date, what changed, action

For landlords with multiple properties, keeping track of which properties are due which checks — and having evidence across the portfolio — is where the operational burden grows. LegioLog is building tools to make this manageable. Join the waitlist to be notified.

This guide covers legionella checks for UK landlords under ACoP L8 and HSE's landlord guidance. This is general compliance guidance, not legal or professional advice. For properties with complex water systems or vulnerable occupants, consult a competent person as defined by ACoP L8.