The Landlord's Guide to Legionella Risk Assessments

Legionella risk assessments are a legal duty for landlords, yet many remain unclear about the requirement, what's actually involved, or why it matters. The reality is straightforward: the Health and Safety Executive (HSE) expects you to assess the risk in your rental property's water system, put in place basic controls, and keep records. That's it. Ignore it, and you're exposed to both enforcement action and potential liability if someone gets ill. Get it right, and it's a modest compliance task that takes a few hours to arrange and costs between £50 and £120.

This guide covers what legionella is, what the HSE expects from you, how the assessment works, and how to maintain a safe water system in your Middlesbrough or Teesside rental property.

What Is Legionella?

Legionella is a bacterium that grows in warm water. The danger zone is 20 to 45 degrees Celsius — the temperature band where it thrives. When water at that temperature is aerosolised (dispersed as fine droplets) through a shower, tap, or cooling system, the bacteria can be inhaled and cause Legionnaires' disease, a severe form of pneumonia that can be fatal.

In commercial buildings with cooling towers and large water systems, legionella outbreaks grab headlines. Domestic rental properties are lower risk, but not no-risk — particularly older Middlesbrough properties with cold water tanks in the loft or hot water cylinders that sit idle between tenancies. The HSE's guidance on legionella applies to anyone controlling a water system that could pose a risk to others, and that includes you as a landlord.

The bacteria grows fastest in stagnant water, water stored at ideal temperatures, and water in biofilm-covered pipes or outlets. Shower heads and flexible hoses are notorious culprits — scale and biofilm build up over months, creating ideal growing conditions. Cold water tanks that are cracked, uncovered, or haven't been cleaned in years are another classic risk.

Your Legal Duty as a Landlord

The Health and Safety at Work etc. Act 1974 creates a general duty to ensure the health and safety of anyone using your property. For water systems, this duty is fleshed out in the HSE's Approved Code of Practice L8 and the associated technical guidance HSG274 Part 2.

What the HSE expects from you:

1. Assess the risk — understand what could go wrong with the water system and where the danger lies
2. Control the risk — put in place reasonable measures to keep temperatures and stagnation under control
3. Record what you've done — document the assessment, the findings, the actions you took, and when
4. Review periodically — reassess if the system changes, if the property sits empty, or every 2–3 years as routine

This applies to every privately rented property in England, whether it's a studio flat or a five-bedroom house. No exceptions. As part of your broader compliance obligations, this sits alongside gas safety certificates, fire safety compliance, and the rest of the landlord compliance checklist.

What Does the Assessment Involve?

A legionella risk assessment for a domestic rental property is straightforward. A competent assessor will spend 30 minutes to an hour on-site and will:

Inspect the cold water supply. If the property has a cold water storage tank (common in older TS1, TS3, and TS5 terraces and semis), the assessor checks whether it has a fitted lid, whether the lid seals properly, whether there's any visible contamination or debris, and whether the tank has been cleaned recently. They'll measure the water temperature — it should be delivered at below 20 degrees Celsius at the tap.

Inspect the hot water system. The assessor checks the boiler or immersion heater settings, measures the temperature at outlets (should exceed 50 degrees Celsius within one minute of running), and checks the condition of any hot water storage cylinder. If a cylinder is fitted, the thermostat should be set to maintain water at 60 degrees Celsius or higher.

Identify dead legs. A dead leg is a section of pipework that's still connected to the system but no longer in use — perhaps an old tap that was capped off, or a shower in a bedroom that's been disconnected. Water sitting in dead legs stagnates and becomes a breeding ground for legionella.

Assess infrequently used outlets. Taps and showers in guest bathrooms, utility rooms, or anywhere else that gets used rarely are flagged because water sits in the pipes and gradually cools, creating ideal growth conditions.

Review the overall system. The assessor checks for cross-connections (where potable and non-potable water could mix), backflow risks, and any other factors that could compromise water quality.

The result is a written report detailing the findings, the risk level, and any recommended actions.

Cost, Timing, and Practicalities

For a standard two or three-bedroom house — the backbone of Middlesbrough's rental stock — a legionella risk assessment costs between £50 and £120. The exact figure depends on the complexity of the water system and the assessor you choose.

The assessment is typically valid for 2–3 years. If the property has been empty for more than a month, or if you've had major work done on the water system, you should arrange a new assessment. Keep a copy alongside your other property compliance documents, alongside your annual safety timeline.

Some landlords opt to do the assessment themselves. The HSE doesn't require a specialist to assess a domestic system — any competent person can do it using HSE templates and guidance. For a straightforward property with a combi boiler and no stored water, that can work. But if your property has a cold water tank, a hot water cylinder, or anything more complex, using a qualified assessor is worth the modest cost for two reasons: you get a professional opinion, and you have third-party documentation that you've met your duty.

Common Risk Factors in Teesside Properties

Middlesbrough's rental stock carries particular legionella risks worth flagging:

Cold water storage tanks in lofts. TS1, TS3, TS5, and TS7 terraces and semis often have cold water tanks in the roof space. Many of these tanks are decades old, uncovered, or damaged. A tank without a proper fitted lid is a legionella risk by definition — debris, insects, and contaminants can fall in, and the open top accelerates algae growth. Getting the tank insulated, sealed, and cleaned is often a landlord's first recommended action.

Hot water cylinders. Properties with stored hot water (rather than on-demand combi boilers) need the cylinder thermostat set to at least 60 degrees. Many older cylinders are set lower to save energy, which undermines legionella risk management. If the assessment recommends raising it, the cost is negligible.

Void periods. A property sitting empty for a week or more sees water stagnate in the pipes. This is a documented risk. The simple control is to run all outlets (all taps, showers, and hoses) for at least 2–3 minutes before a new tenant moves in. Water should run clear and warm. It takes 10 minutes and costs nothing.

Shower heads and flexible hoses. Scale and biofilm accumulate fast on these. Replacing them at each tenancy change or descaling them regularly is a practical control measure. Many landlords include a new shower head as part of the tenancy refresh anyway.

Control Measures: What to Do

Most of the controls needed are simple and cheap:

• Hot water thermostat at 60°C. Set the cylinder thermostat to maintain 60 degrees. Check that water reaches 50 degrees at the tap within one minute of running.
• Cold water stored below 20°C. If you have a tank, ensure it's insulated and kept in a cool space (lofts can exceed 20 degrees in summer, so insulation matters).
• Remove or cap dead legs. Any pipework no longer in use should be removed or clearly capped off so water can't stagnate in it.
• Flush after void periods. Run all outlets for 2–3 minutes before a new tenant moves in.
• Replace old cold water tanks. If the assessment flags a tank as damaged, corroded, or uncovered, replacing it is often the recommendation. A new tank with insulation and a sealed lid costs [STAT NEEDED: cost of replacement cold water tank installed] fitted and removes a major risk.
• Clean or replace shower heads. Descale regularly or replace at tenancy change.
• Advise tenants. Let them know to run any infrequently used outlets weekly, especially guest bathrooms.

Keep records of all actions taken — dates, what was done, and by whom. If you use a letting agent, they should manage this on your behalf and provide you with copies.

Frequently Asked Questions

Is a legionella risk assessment required if I have a combi boiler?

Yes. Even a combi boiler system needs assessment because there may be cold water storage, dead legs in old pipework, or other risk factors. The assessment might conclude that risk is very low and no additional controls are needed, but the assessment itself is a legal requirement.

How often do I need to reassess?

Every 2–3 years as a matter of routine. Sooner if the property has been vacant for more than a month, if major plumbing work is done, or if the tenancy changes and a new occupant pattern (e.g., more people in the property) alters water use.

Can I do the assessment myself to save money?

You can if you're confident you understand the HSE guidance and your system is very simple (modern combi boiler, no storage tanks, regularly used outlets). For anything more complex, paying £50–120 for a qualified assessor is worth it for certainty and documentation.

What if the assessment recommends expensive work?

The assessor will prioritise recommendations. High-risk items (like a cracked cold water tank) often must be fixed. Lower-priority items (like descaling a shower head) can be done gradually. If you're uncertain whether a recommended action is truly necessary, ask the assessor to explain the risk and get a second opinion.

What happens if I don't carry out the assessment?

You're in breach of the Health and Safety at Work Act. The HSE can issue an Improvement Notice (giving you a deadline to comply) or, in serious cases, a Prohibition Notice. More importantly, if a tenant contracts Legionnaires' disease and your property is later found to have an unassessed water system, your liability exposure is much greater. Understanding letting regulations penalties is important across all compliance areas.

Who counts as a "competent person" to carry out the assessment?

The HSE defines a competent person as someone with the knowledge, training, and experience to manage legionella risk. For domestic properties, this includes qualified plumbers, heating engineers, or specialist legionella assessors. They should be able to demonstrate training in HSE guidance or similar. Many engineers hold Water Hygiene certification.

Do I need to tell my tenants about the legionella assessment?

You don't have a legal requirement to disclose the assessment to tenants, but it's good practice to let them know you've had it done and to include basic advice in the tenancy pack (e.g., "please run infrequently used outlets weekly"). Transparent landlords typically fare better with tenant relations.

What's the difference between a legionella assessment and testing the water?

An assessment is a visual and technical inspection of the system and controls. Testing the water for legionella bacteria is a separate step, usually done only on higher-risk systems (like large commercial buildings or properties where legionella has been detected). For a domestic rental property, the HSE expects risk assessment and control measures, not routine water testing.

Getting It Done

Legionella compliance is not complicated. You need the assessment done, the findings documented, recommended actions carried out, and records kept. It's a one-off task every 2–3 years plus annual upkeep (flushing after void periods, maintaining temperatures, cleaning outlets).

If you let your property through a managing agent, check that they include legionella assessment as part of their compliance service. If you manage it yourself, contact a qualified plumber or legionella assessor in Middlesbrough and get it booked in. Total cost and time: around £100 and a couple of hours of admin.

The compliance landscape for landlords has shifted significantly in recent years. If you're not already managing these duties as part of your routine, now is the time. Legionella fits into that same framework — reasonable precautions, documented evidence, and peace of mind for you and your tenants.