Short answer: for most rented homes, yes. HSE’s guidance for landlords says that most landlords can assess the risk themselves and do not need to be professionally trained or accredited. The assessment is a matter of understanding your own water system, writing down what you found, and putting in place the simple controls that follow.
Where it stops being a do-it-yourself job is at complexity and vulnerability: shared or communal systems, large buildings, or occupants at higher risk. This guide covers what to look at, what to write, and where that line is.
What “competent” means here
The law asks for the person doing the assessment to be competent, and for a simple domestic water system HSE is explicit that a landlord can be that person. Competent means you understand how this system is put together, what makes legionella bacteria multiply, and what the guidance asks for. It does not mean holding a qualification.
The bacteria multiply in water that is warm and still. Every control measure in the guidance is a way of keeping water either hot, cold, or moving. If you hold that sentence in your head while you walk the property, the assessment mostly writes itself.
Walk the system
Start at the incoming main and follow the water. Answer each of these and write the answer down:
Where does the cold water come from? Straight from the mains to every cold tap, or via a storage tank in the loft? Cold water fed directly from a wholesome mains supply, with no stored water, removes a whole category of risk on its own, and HSE names it as a control measure in itself. If there is a tank: is it lidded, insulated, clean inside, and in a space that stays cool?
Where is the hot water made? A combi boiler heats water on demand and stores none. A cylinder (calorifier) stores it, and stored hot water is where temperature control matters: does the cylinder run at 60 °C or above? Does hot water circulate around a loop, or run to each tap and sit?
What is not being used? Redundant pipework, a capped-off run to a removed appliance, an outside tap nobody opens, an en suite in a spare room, a shower in a flat that has stood empty. Water sitting still in a dead leg is the classic source. HSE’s suggested controls include removing redundant pipework and flushing the system through before letting.
What are the temperatures? Run the hot tap furthest from the cylinder and see whether it reaches 50 °C within a minute. Run the cold tap furthest from the main and see whether it is below 20 °C within two minutes. Those are the thresholds the monitoring regime uses, and a first pair of readings tells you whether the system is behaving. What temperature should hot water be? has the full set.
Who lives there? Legionnaires’ disease is more dangerous for older people, smokers, and people with lung conditions or weakened immune systems. HSE describes the risk in typical residential settings with small domestic water systems in regular use as generally low; the occupants can move it.
Write it down
The assessment does not need to be long. For a flat with a combi boiler and mains cold it can be a single page. A practical structure:
- The system, in a few lines: how cold arrives, how hot is made, whether anything is stored or circulated.
- What you found: tank condition, cylinder temperature, any dead legs or unused outlets, the two tap readings, anything about the occupants that raises the risk.
- The controls that follow, with who does them and when.
- The date, your name, and when you will next review it.
HSE’s own list of simple measures for domestic systems is a good checklist for point 3: flush the system before letting, keep debris out of the tank, keep hot water at the right temperature, remove redundant pipework, and ask tenants to clean showerheads regularly.
What you do not need to do
Test the water. HSE says testing is not usually required for domestic hot and cold water systems and is only needed in very specific circumstances. A sample tells you about that outlet on that morning; the controls are what manage the risk.
Buy a certificate. There is no such document in law. Health and safety law does not require a landlord to obtain or produce a legionella test certificate. Do I need a legionella certificate? covers what to say when someone offers you one.
Set up the full monitoring regime for every property. HSG274 Table 2.1’s monthly checks are for systems where temperature control is the control measure, typically with stored hot water, circulation or a tank, and even then the document describes the table as an indication of frequency, with the property’s assessment deciding what is actually done. A combi-boiler flat may reasonably conclude that occasional checks and a flush between tenancies are proportionate.
When to get help
Do the assessment yourself when the system is simple and you understand it. Get a water hygiene professional in when:
- the system is communal or shared: a block with a central cylinder, several risers, or a shared cold water tank;
- the building is large or complicated enough that you cannot confidently trace where the water goes;
- occupants are particularly vulnerable, for instance supported housing or a care setting, where the tolerance for error is lower;
- you have found something that worries you, such as a persistently warm cold supply, and want a second opinion.
A reputable company will assess and advise. Ask them what they will look at and what you get back, and be wary of any proposal that leads with routine sampling for an ordinary let.
Review it
HSG274 says to review the assessment regularly and whenever there is reason to think it is no longer valid (para 14, p3). It does not set a fixed interval. The triggers that matter are changes to the system or its use: a new boiler or cylinder, a bathroom reconfigured, a long void period, a change of tenants. Put the next review date on the assessment so it does not depend on memory.
Where the app fits
Legionella Logger does not do the assessment, and it says so on every screen where it could be mistaken for one. What it does is the part that comes after: the schedule of checks the assessment calls for, the timed readings, the pass or fail against the right threshold, and a PDF log that shows what was done. If your assessment concludes that monitoring is proportionate for a property, that is the record it keeps.
Sources
HSE: legionella and landlords’ responsibilities is the short, authoritative starting point. The Approved Code of Practice is L8 and the technical guidance is HSG274; both are free. Landlord legionella duties sets the assessment in the context of the whole duty.
Statements about HSE guidance checked against hse.gov.uk on 11 September 2026; HSG274 references against the archived HSE PDF, with printed page numbers. Contains public sector information licensed under the Open Government Licence v3.0. This is general information about published guidance, not a legionella risk assessment and not legal advice. Plan CD is not affiliated with the Health and Safety Executive.