How Often Do You Need a Legionella Risk Assessment?

“Every two years” is the answer most landlords have heard, and it’s a reasonable starting point, but it isn’t the whole story. The HSE’s ACOP L8 guidance treats two years as a maximum interval for a full review, not a fixed schedule you can set and forget. Several things can bring that date forward.

The baseline: at least every two years

For a typical domestic or light commercial property with a stable water system and no changes in use, a full Legionella Risk Assessment review every two years satisfies the ACOP L8 recommendation. That’s the interval to plan around as a default, before checking whether any of the triggers below bring it forward.

What shortens the interval

A review should happen sooner than the two-year mark if any of the following apply:

• A change of tenant. New occupants mean a new pattern of water use, and it’s good practice to confirm the system is still low-risk before they move in.
• An extended void period. If a property has sat empty, water in the pipework can stagnate, exactly the condition Legionella needs to establish itself.
• Changes to the water system. New pipework, a replaced boiler or cylinder, or any plumbing work can alter how water moves (or doesn’t move) through the property.
• A change of use. Converting a property into an HMO, or adding rooms with their own water outlets, increases the number of outlets and the risk of some falling out of regular use.
• Any sign of a problem. Discoloured water, unusual smells, or a previous assessment flagging borderline temperatures are all reasons to review sooner rather than wait out the two years.

Why “infrequently used outlets” matter so much

Of all the risk factors an assessment looks for, dead legs and infrequently used outlets are consistently the most common finding, particularly in rented properties. A spare room, an outbuilding, or a shower that a tenant simply doesn’t use can sit stagnant for weeks, and it’s precisely that stagnant water, sitting in the temperature range Legionella bacteria favour, that a risk assessment is designed to catch.

Keeping a record

Beyond the legal minimum, keeping a documented history of assessments and any remedial action taken is what protects you if a dispute or incident ever arises. A single old certificate isn’t enough on its own, what matters is being able to show an ongoing, proportionate approach to managing the risk.

If you’re not sure when your last assessment was carried out, or whether recent changes to a property mean you’re due a review sooner than planned, get in touch and we can advise based on your specific situation.