Can I Do My Own Legionella Risk Assessment? Self-Assessment Guide for Landlords

The short answer: yes, for most standard residential properties. HSE confirms that landlords can assess legionella risk themselves, provided they are competent to do so. There is no legal requirement to hire a specialist for a simple domestic hot and cold water system.

The practical question is whether self-assessment is right for your specific property. Here is how to decide, how to do it if it is, and when to pay a professional instead.

What "competent" means for self-assessment

ACoP L8 requires that the person conducting the risk assessment is "competent." For a self-assessing landlord, this means understanding three things:

1. How your water system works — where water enters the property, how it is stored (if at all), how it is heated, and how it reaches each outlet
2. What conditions allow legionella to grow — stagnant water, temperatures between 20°C and 45°C, biofilm, scale, and sediment
3. What control measures prevent growth — temperature management, regular use or flushing, cleaning, and removing dead legs

You do not need a formal qualification. You do not need to attend a course (though courses exist if you want the confidence). You need to understand the system you are assessing well enough to identify risks and implement controls.

When self-assessment is appropriate

Self-assessment works well for properties with:

System characteristic	Self-assess?	Notes
Combi boiler (no stored hot water)	Yes	Lowest risk — water heated on demand, no storage
Stored hot water cylinder	Yes	Check thermostat is set to 60°C+, check delivery temperatures
Direct mains cold water (no tank)	Yes	Low risk — no cold water storage
Cold water storage tank	Caution	Inspect tank condition, lid, insulation; if large or inaccessible, consider specialist
Single dwelling (flat/house)	Yes	Simple system, limited outlets
Small HMO (up to ~6 beds)	Yes	More outlets and shared bathrooms, but manageable
Large HMO (7+ beds, multiple floors)	Consider specialist	Complex pipework, potential dead legs from conversion

When to hire a specialist

Do not self-assess if any of the following apply:

• The building has a cooling tower or evaporative condenser — these are high-risk systems requiring specialist knowledge
• There is a large cold water storage tank (300+ litres) — tank condition, insulation, and incoming mains temperature need technical assessment
• The property serves vulnerable occupants — care homes, nurseries, sheltered housing. Higher regulatory scrutiny and higher consequences of failure
• The water system has been significantly modified — conversions, extensions, or HMO adaptations often create dead legs and unknown pipe routes
• You genuinely do not understand your water system — if you cannot describe how hot water reaches the shower, self-assessment will produce an incomplete document
• Previous assessments have found issues — persistent temperature failures or positive legionella samples need specialist investigation

A professional risk assessment for a standard residential property typically costs £75–£150. For a complex system or large building, expect £150–£500+. Compare this to the cost of your time and the risk of missing something in a system you do not fully understand.

How to do a self-assessment: step by step

Step 1: Map your water system

Before assessing risk, document what you have:

• Water supply: mains cold water, private supply, or both
• Hot water generation: combi boiler, stored cylinder (note capacity and thermostat setting), immersion heater, or point-of-use heaters
• Cold water storage: direct mains feed (most common in modern properties) or header tank (common in older properties — check the loft)
• Outlets: list every tap, shower, bath, and WC cistern with its location
• Dead legs: any capped-off pipework from removed sinks, showers, or appliances

Step 2: Check temperatures

Temperature is the single most important control measure. Legionella bacteria multiply between 20°C and 45°C and are killed above 60°C. Check:

What to measure	Target	How
Hot water storage (cylinder thermostat)	60°C or above	Read the thermostat dial or use a surface thermometer
Hot water at outlet (nearest tap to cylinder)	50°C or above within 1 minute of running	Run the hot tap, measure with a thermometer
Hot water at outlet (furthest tap from cylinder)	50°C or above within 2 minutes	Same method — this checks for temperature loss in long pipe runs
Cold water at outlet	Below 20°C within 2 minutes of running	Run the cold tap, measure after 2 minutes

If hot water at any outlet does not reach 50°C, investigate — the cylinder thermostat may be set too low, or there may be a thermostatic mixing valve (TMV) restricting temperature.

If cold water is above 20°C, check whether pipes run through warm spaces (airing cupboards, near heating pipes) or whether the incoming mains temperature is elevated (can happen in summer in some areas).

Step 3: Identify stagnation risks

Water that sits still in pipes for extended periods is a legionella risk. Check for:

• Infrequently used outlets — a spare bathroom that is rarely used, a utility room tap. Any outlet unused for 7+ days needs weekly flushing
• Dead legs — pipework leading to removed or capped-off fixtures. These trap stagnant water. Ideally, dead legs should be removed; if not, they must be flushed regularly
• Void periods — when the property is empty between tenants. Flush all outlets before new tenants move in. For extended voids (weeks to months), consider draining the system or arranging periodic flushing

Step 4: Check system condition

Physically inspect accessible components:

• Cold water storage tank (if present): does it have a tight-fitting lid? Is it insulated? Is there debris, scale, or discolouration? Is the overflow screened against insects?
• Hot water cylinder: any visible corrosion? Is the thermostat functional?
• Showerheads: any visible scale or biofilm? Showerheads should be descaled and disinfected quarterly — they create fine aerosols, which is the primary inhalation route for legionella
• Pipework: any visible corrosion, leaks, or insulation gaps?

Step 5: Document your findings

Write up what you found, what risks exist, and what you are doing about each one. A compliant risk assessment document must include:

1. Property details and water system description
2. Hazards identified (temperature issues, stagnation risks, system condition)
3. Who is at risk (tenants, with note of any vulnerable occupants)
4. Control measures in place or planned
5. Monitoring schedule (what checks, how often, who does them)
6. Named responsible person
7. Review date (within two years)

LegioLog's Risk Assessment Template Generator produces a structured document covering all seven sections, pre-populated with standard hazards and control measures for your property type.

Step 6: Set up ongoing monitoring

The risk assessment is the starting point, not the finish line. After the initial assessment, you must:

• Check temperatures monthly at sentinel outlets (one hot and one cold at the nearest and furthest points from the heat source)
• Flush unused outlets weekly — run both hot and cold for at least two minutes
• Descale showerheads quarterly
• Record every check — date, reading/action, who did it

For a single property, a simple spreadsheet or paper log works. For multiple properties, tracking becomes the main challenge — knowing which checks are due, which outlets need flushing, and whether anything has been missed across the portfolio.

Common self-assessment mistakes

Copying a generic template without editing it. A risk assessment must be specific to your property. A blank form with "insert address here" does not demonstrate competence.

Ignoring dead legs. If the previous owner removed a downstairs toilet but left the pipework capped off, that is a stagnation risk. Walk the property and check for capped pipes.

Setting the cylinder too low. Some landlords lower the cylinder thermostat to reduce energy costs or scald risk. Below 60°C storage creates legionella growth conditions. If scald risk is a concern (children, elderly tenants), use TMVs at the outlet rather than reducing the cylinder temperature.

Skipping the ongoing monitoring. The assessment itself is meaningless without evidence of follow-through. An inspector will ask for temperature logs and flushing records, not just the initial document.

Not reviewing. The assessment needs revisiting at least every two years, or after any change: new boiler, bathroom modification, change of tenant type, period of vacancy. See our guide to review frequency.

The cost comparison

Approach	Initial cost	Ongoing cost	Best for
Self-assessment	Your time (1–2 hours for a simple property)	30 minutes/month for monitoring	Landlords with 1–5 simple residential properties
Professional assessment	£75–£150 per property	Same monitoring obligation applies	Landlords who want a specialist opinion, or properties with complex systems
Annual managed service	£200–£600/year per property	Included in contract	Landlords who want the monitoring done for them, or larger portfolios

The critical point: ongoing monitoring costs are the same regardless of who does the initial assessment. Whether you self-assess or hire a professional, the monthly temperature checks and weekly flushing are your responsibility unless you pay for a managed service.

Get started

LegioLog's free tools can help with self-assessment:

• Risk Assessment Template Generator — creates a property-specific assessment document
• Temperature Compliance Checker — verify readings against ACoP L8 thresholds
• Flushing Schedule Calculator — generate a flushing timetable for your outlet inventory

For the full regulatory context, see our ACoP L8 and HSG274 guide.

This guide covers self-assessment of legionella risk for landlords in England, Wales, and Scotland under ACoP L8. Scottish landlords should also note the additional obligations under the Repairing Standard — see our Scotland-specific differences guide. This is general compliance guidance, not legal or professional advice — for complex systems or properties with vulnerable occupants, consult a competent person as defined by ACoP L8.

Sources

• HSE — Legionella and landlords' responsibilities
• HSE — ACoP L8: Legionnaires' disease
• HSE — Identify and assess sources of risk