How much does a legionella risk assessment cost?

A professional legionella risk assessment usually costs £75–£200 for a rented house or flat. But for most landlords, the real cost can be nothing: the Health and Safety Executive (HSE) says most landlords can assess the risk themselves, and there’s no legal requirement for a certificate or water testing.

You do have to assess the risk. You just don’t have to pay someone to do it.

Typical legionella risk assessment prices

These are typical ranges from UK price guides and providers, not quotes. London and the South East are usually at the top of the range.

What affects the price

• Size and complexity of the water system. A flat with a combi boiler has very little stored water. A house with a cold water tank in the loft and a hot water cylinder takes longer to assess.
• Number of bathrooms and outlets. More taps and showers means more to check.
• HMOs. Shared houses often have larger systems and more people using them, so assessments cost more.
• How many properties. Many assessors and agents discount per property for a portfolio.
• Extras. Some firms try to sell water sampling or annual “certificates” alongside the assessment. For a normal home these are usually not needed.

Is a legionella risk assessment a legal requirement?

Yes, but not in the way many sites suggest. Under health and safety law, landlords have a duty not to expose tenants to health risks, which includes the risk from legionella bacteria in the water system. HSE guidance says this means landlords must assess the risk, and that this “does not require an in-depth, detailed assessment”.

What the law does not require:

• A certificate. There’s no legal “legionella test certificate” for rented homes.
• A professional. HSE says most landlords “do not need to be professionally trained or accredited”.
• Water testing. Testing or sampling is not usually needed for domestic systems.
• A written record, unless you’re an employer with 5 or more employees. HSE still recommends keeping one, and it’s sensible to do so.

So if a company tells you a professional assessment or certificate is a legal requirement, that isn’t correct. You may still choose to pay for one, but it’s a choice.

What a DIY legionella risk assessment covers

The aim is to spot where water could sit still or stay lukewarm, because that’s where legionella bacteria can grow. Walk through the property and note:

• Water tanks. Is there a cold water tank, for example in the loft? Check it has a well-fitting lid, and that it’s clean, with no debris or rust.
• Water temperatures. Hot water should be hot and cold water should be cold. Check the boiler or hot water cylinder is set to heat water properly, and that cold pipes aren’t running near heat sources.
• Little-used outlets. Spare bathrooms, outside taps or showers that are rarely used can let water stagnate. Note them and tell the tenant to run them regularly.
• Showerheads. Showerheads and hoses can build up scale. They should be cleaned and descaled regularly.
• Void periods. If the property is empty between tenancies, water sits in the pipes. Flush the system through by running all taps and showers before the new tenant moves in.

Write down what you found, any action you took, and the date. Give your tenant simple advice too, such as running little-used outlets and telling you if the hot water isn’t heating properly. Review the assessment if anything changes, such as a new boiler or a long empty period.

When paying a professional makes sense

A DIY assessment is fine for most standard flats and houses. Paying a professional assessor is worth considering if:

• You let an HMO with several bathrooms and more occupants.
• The water system is complex, for example with large stored-water tanks, multiple cylinders or communal supplies.
• You have a portfolio and want a consistent, documented process across every property.
• You’re not confident assessing the system yourself, or you’d simply rather have a professional record on file.

What happens if you don’t assess the risk

HSE and councils don’t routinely inspect rented homes for legionella. But if a tenant catches Legionnaires’ disease, you could be prosecuted under health and safety law. You would need to show that you assessed the risk and took steps to control it, which is why keeping a dated record is worthwhile even though the law doesn’t always require one.

Ways to keep the cost down

• Do it yourself. For most single lets, a careful walk-through and a written note costs nothing and meets HSE guidance.
• Skip the extras. Don’t pay for water sampling or an annual “certificate” unless there’s a specific reason.
• Bundle it. If you do want a professional, some firms offer a discount when booked with a gas safety certificate or EICR, or for several properties at once.
• Set a reminder to review your assessment between tenancies. Use our free certificate reminders, and see the landlord compliance checklist for everything else you need before a tenant moves in.