A legionella risk assessment checks whether a property's water system could allow Legionella bacteria to grow and spread. Landlords must assess and control this risk under health and safety law, following HSE's ACOP L8 and HSG274. There is no legal legionella certificate: the written assessment is your evidence. BritCertify assessments start from £299 inc. VAT for a one or two bedroom property.
Do London landlords need a legionella risk assessment?
Yes. Landlords must assess and control the risk of exposure to Legionella bacteria for their tenants. A proportionate written risk assessment, reviewed regularly, is the evidence HSE expects to see.
The duty comes from the Health and Safety at Work etc. Act 1974 and the Control of Substances Hazardous to Health Regulations 2002 (COSHH). HSE’s Approved Code of Practice L8 and its technical guidance HSG274 explain how to meet it. There is no legal document called a legionella certificate. What protects you is an assessment that reflects the actual water system, plus evidence that you have acted on it.
For most single flats and houses the risk is low, and the assessment can be simple. That does not mean it can be skipped: low risk is a conclusion you reach by assessing the system, not an assumption. HSE’s guidance for landlords, things to consider, sets out the expectations in plain terms.
How does legionella become a risk in a home?
Legionella bacteria multiply in water between 20°C and 45°C, especially where water sits still and where there is sludge, scale or biofilm to feed on. People are infected by breathing in fine droplets of contaminated water, most commonly from showers and spray taps.
So the assessment focuses on three questions: is water being stored or held at temperatures that allow growth, is any water stagnating, and where could contaminated water be turned into spray?
What does a legionella risk assessment check?
The assessor traces the hot and cold water system from the incoming main to each outlet, inspects any storage, and measures temperatures. These are the main areas covered:
| Area | What we look at | Why it matters |
|---|---|---|
| Cold water storage tanks | Lid, insulation, screened overflow and vent, debris, size compared with daily use | Warm, dirty or oversized tanks let water stagnate and bacteria grow |
| Hot water cylinder | Stored temperature, thermostat setting, condition | Hot water should be stored at 60°C or higher |
| Outlet temperatures | Hot and cold readings at taps and showers | Hot should reach 50°C within one minute; cold should fall below 20°C within two minutes |
| Dead legs and redundant pipework | Pipes left behind after bathrooms or kitchens were moved | Water in a dead leg never flows, so it stagnates |
| Showerheads and hoses | Scale, biofilm and condition | Showers create the fine spray that carries bacteria |
| Little-used outlets | Spare bathrooms, outside taps, utility sinks, empty rooms | Outlets not used for a week or more should be flushed weekly |
The assessment also considers who lives in the property. Older tenants, or anyone with a weakened immune system, are more vulnerable, which raises the importance of the controls even in a simple system.
Access is worth planning in London. Cold water tanks often sit in a shared loft above a converted house, reached through the top-floor flat, or in a roof-level plant room in a purpose-built block. If the tank serving your flat is outside it, tell us when you book so we can arrange access with the neighbour or managing agent, rather than recording the tank as not inspected.
Which London properties carry a higher legionella risk?
Risk depends far more on the water system than the postcode, but some London property types come up again and again on our assessments:
- Converted Victorian and Edwardian houses: a loft tank that once fed the whole house may now serve only one flat, so water turns over slowly. Old cement water tanks in these lofts can also be an asbestos concern, which is worth checking with an asbestos survey.
- HMOs: several bathrooms, changing occupancy and rooms that sit empty between lets all create stagnant outlets. Pair the assessment with your HMO fire risk assessment so both are current for licensing.
- Properties left empty: a void of a few weeks between tenancies is long enough for water to stagnate throughout the system.
- Gravity-fed systems with cylinders: stored hot water must be kept hot enough, and a cylinder turned down to save energy can sit in the growth range.
- Remodelled flats: where a kitchen or bathroom has moved, redundant pipework is often capped off rather than removed, leaving a dead leg.
Flats with a combination boiler and no stored water are generally lower risk, because hot water is heated on demand. The cold supply, showers and any little-used outlets still need to be considered.
How often should a legionella risk assessment be reviewed?
There is no fixed legal interval. The assessment should be reviewed regularly and whenever something changes that could affect the risk. Your report gives a recommended review date based on the system and the occupants.
| Trigger | Why review |
|---|---|
| Changes to the water system | New boiler, cylinder, tank, bathroom or kitchen can create new risks |
| A long empty period | Stagnation throughout the system; flush before re-letting |
| A change in occupants | Vulnerable occupants raise the importance of controls |
| Conversion to an HMO | More outlets and variable use change the risk profile |
| Reaching the review date | Confirms the controls are still working |
What should landlords do between assessments?
Most control measures are simple and cost little. Keep the boiler or cylinder set so stored hot water reaches 60°C, and have the system maintained; a regular boiler service is a sensible part of that. Flush every tap and shower before a new tenant moves in after a void, taking care to minimise spray. Remove or shorten redundant pipework when other plumbing work is being done.
Tell your tenants about the risk and their part in controlling it: running little-used taps, cleaning and descaling showerheads, and reporting hot water that is not hot or cold water that is not cold. Keep a simple record of what you have done, as it forms part of your evidence alongside the assessment.
How much does a legionella risk assessment cost in London?
Our legionella risk assessments start from £299 inc. VAT for a one or two bedroom property and £349 for three or four bedrooms. Larger homes, HMOs and commercial premises are quoted on the number of outlets, tanks and bathrooms. Use our quote form and tell us whether the property has a combi boiler, a cylinder or a loft tank.
Legionella risk assessment prices in London (inc. VAT)
| Option | Price (inc. VAT) | Notes |
|---|---|---|
| 1–2 bedroom property | £299 | Flats and small houses |
| 3–4 bedroom property | £349 | Family houses and maisonettes |
| Larger properties and HMOs | Quote | Based on the number of outlets, tanks and bathrooms |
| Commercial premises | Quote | Offices, shops, gyms and other business premises |
All prices include VAT. Central London parking or Congestion Charge may be added. We always confirm before booking.
Book this serviceWhat's included
- On-site assessment of the hot and cold water system
- Temperature checks at hot and cold outlets
- Inspection of accessible cold water tanks and the hot water cylinder
- Identification of dead legs, little-used outlets and other risk factors
- Written risk assessment following HSE ACOP L8 and HSG274
- Practical control measures and a recommended review date
- Simple guidance you can share with tenants
How it works
Book and describe the system
Tell us the bedrooms, occupancy and whether there is a combi boiler, cylinder or loft tank. We confirm the price inc. VAT.
Site assessment
We trace the water system, inspect tanks and the cylinder, measure outlet temperatures, and note dead legs, showers and little-used outlets.
Written assessment
We record the risks found, who could be affected and the control measures needed, following HSE ACOP L8 and HSG274.
Ongoing control
You receive the report with clear actions, a simple flushing and checking routine, and a recommended review date.
Legionella Risk Assessment: frequently asked questions
Is a legionella certificate a legal requirement for landlords?
No. There is no legal legionella certificate. The legal duty under the Health and Safety at Work etc. Act 1974 and COSHH 2002 is to assess and control the risk of exposure for your tenants. A proportionate written risk assessment, reviewed regularly, together with records of the controls you put in place, is the evidence HSE expects.
How often does a legionella risk assessment need to be done?
There is no fixed legal interval. HSE expects the assessment to be reviewed regularly and whenever something changes, such as new plumbing, a new boiler or cylinder, a long empty period or more vulnerable occupants. Your report includes a recommended review date based on the system and how the property is used.
Is a flat with a combi boiler low risk?
Generally, yes, because a combi heats water on demand and there is no stored hot water. The cold supply, showers, little-used outlets and any redundant pipework still need to be considered, so the flat still needs an assessment. For most combi flats it is short and straightforward, with a few simple controls.
What temperatures should hot and cold water be?
HSE guidance says hot water should be stored at 60°C or higher and reach at least 50°C at outlets within one minute of running, or 55°C in healthcare premises. Cold water should be below 20°C within two minutes. Legionella multiplies between 20°C and 45°C, so the aim is to keep water outside that range.
What should I do before re-letting a property that has been empty?
Flush the whole system before the new tenant moves in. Run every hot and cold tap and shower until the temperature stabilises, taking care to minimise spray, and check the boiler or cylinder is heating water properly. If the property was empty for a long period or the system has changed, review the risk assessment as well.
Do HMOs need a legionella risk assessment?
Yes. The same duty applies, and HMOs usually need a more detailed assessment because they have more bathrooms, more outlets and occupancy that changes through the year. Empty rooms between lets create stagnant outlets. Check your HMO licence conditions with your council, and keep the assessment alongside your other HMO safety records.
Sources and official guidance
Written and checked by the BritCertify technical team. Last reviewed 6 October 2026.