Legionella questions, answered properly

Yes, if you're an employer, a landlord or otherwise in control of premises with a water system, you must assess the risk from Legionella and control it. The duty comes from the Health and Safety at Work etc. Act 1974 and the COSHH Regulations 2002, and the practical detail is in HSE's ACOP L8. The law doesn't say the assessment has to be written by a contractor, but you do need to be able to show it was done and acted on.

ACOP L8 is HSE's Approved Code of Practice for controlling Legionella bacteria in water systems, currently the 4th edition published in 2013. It explains what the law expects: assess the risk, appoint a competent responsible person, write a scheme to prevent or control the risk, put it into practice and keep records. Following it isn't compulsory, but if you don't, you'd need to show you've done something equally good. You can read it free on the HSE website.

HSG274 is HSE's technical guidance that sits alongside ACOP L8, and for most buildings Part 2 is the one that matters. HSG274 comes in three parts: Part 1 covers evaporative cooling systems, Part 2 covers hot and cold water systems, and Part 3 covers other risk systems such as spa pools, humidifiers and vehicle washes. Homes, HMOs, offices, schools and care homes are all Part 2 territory, which sets out the temperatures, checks and frequencies we work to.

The duty holder is whoever controls the premises or the water system, usually the employer, the landlord or the managing agent acting for them. In a block of flats that might be the freeholder or management company for the shared parts, and the landlord for each let flat. The duty holder can delegate the day-to-day work, but not the legal responsibility. ACOP L8 also expects a named responsible person to manage the controls.

No, there's no such thing as a legal Legionella certificate. What you need is a suitable risk assessment, the controls it recommends, and records showing those controls are being carried out. Some councils, insurers and letting agents ask for "a certificate", and what they usually mean is a current risk assessment report. We'll give you a dated report you can hand over.

You could be breaking health and safety law, and if someone falls ill the consequences can be serious for them and for you. HSE and local authorities enforce the law and can issue notices or prosecute, whether or not anyone has been harmed. In practice most problems come to light through an inspection, an insurance or licensing request, or a poor sample result. A sensible assessment and simple routine checks keep you well clear of that.

They carry a higher risk and have their own guidance, so they need a specialist assessment. Cooling towers and evaporative condensers are covered by HSG274 Part 1, and you must tell your local authority about them under the Notification of Cooling Towers and Evaporative Condensers Regulations 1992. Spa pools and hot tubs fall under HSG274 Part 3. If your site has any of these, tell us when you get in touch so we can plan the right assessment.

Yes, landlords of rented homes have a duty to assess and control the risk from Legionella for their tenants. HSE is clear that for most ordinary homes the assessment is simple and the controls are straightforward, so it shouldn't be a big job. You don't need routine water testing in a typical let. Our guide on whether landlords need a Legionella risk assessment goes through it in more detail, and HSE's Legionella pages cover landlords too.

Yes, if you understand the water system and know what to look for, you can assess a simple property yourself. HSE doesn't require landlords to use a contractor. Many choose to anyway, because a professional report is easier to show a council, agent or insurer, and because tanks, cylinders and dead legs are easy to miss if you don't do this every day. If you have several properties, a portfolio approach keeps the cost sensible.

Yes, HMOs have the same Legionella duty as any rented home, and the risk is often higher. Shared bathrooms, more outlets, rooms left empty between tenants and older plumbing all add up. Many councils ask to see an assessment as part of HMO licensing, and conditions vary from one council to the next, so always check yours. Our article on HMO licensing and Legionella explains what councils tend to look for.

Yes, if you let a property to paying guests you have the same duty as any other landlord. Holiday lets often carry more risk because they sit empty between bookings and over the quiet season, so water stands still in the pipes. The fix is mostly a good changeover routine: run every tap and shower before guests arrive and keep the hot water hot. See our guide to Legionella in holiday lets.

Tell them what Legionella is in plain terms and what you'd like them to do. That usually means running taps and showers for a couple of minutes after they've been away, keeping shower heads clean, not turning the hot water temperature down and reporting any problems with the boiler or cylinder. We include short tenant guidance with every landlord assessment so you don't have to write it yourself.

Managing agents need to make sure the duty is covered, either by arranging the assessment and checks themselves or by being clear in writing that the landlord is doing it. Where an agent manages a property, they often take on day-to-day control, which can make them a duty holder alongside the landlord. The simplest approach is to agree who does what in the management contract, keep the reports on file and diarise reviews and void-property flushing.

A Legionella risk assessment is a survey of the whole water system to find anywhere bacteria could grow or be spread as spray. We look at the incoming mains, cold water tanks, water heaters and cylinders, pipework, showers and outlets, take temperatures and note dead legs, little-used outlets and anything that's in poor condition. You then get a written report with the risks ranked, a schematic of the system and a written scheme of control that says what to check and how often.

It should be reviewed regularly and whenever there's reason to think it's no longer valid, rather than on a fixed legal timetable. ACOP L8 lists triggers such as changes to the water system or how the building is used, new information about risks, a positive sample, a case of illness or controls that aren't working. Many duty holders also review every two years as good practice. Our article on how often to review a Legionella risk assessment has more.

No, testing and assessment are different jobs. A risk assessment looks at the whole system and how it's managed, to find where bacteria could grow. Water sampling is a laboratory test of water from one outlet at one moment. Sampling is useful for checking that your controls work, and it's expected in some settings such as healthcare, but it doesn't replace an assessment. See our water sampling page.

Someone with the knowledge, training and experience to understand your type of water system and the guidance that applies to it. ACOP L8 talks about competence rather than a specific qualification. For a simple flat that's a modest bar. For a care home, school or hospital the assessor needs a much deeper understanding of things like TMVs, calorifiers and vulnerable users, and in healthcare HTM 04-01 applies as well.

The law is the same, but the risks aren't. Care homes have vulnerable residents and a scalding risk as well as a Legionella one, so TMVs and careful temperature control matter (see HSE's HSIS6). Schools are mostly about long holiday closures. Offices with hybrid working often have quiet floors with outlets that hardly get used. Our article on care homes, schools and dental practices covers this, and inspectors such as the CQC will expect your water safety records to be in order.

Hot water should be stored at 60°C or above and reach outlets at 50°C or more within one minute, and cold water should be below 20°C within two minutes. Those are the figures in HSG274 Part 2. Healthcare premises aim for 55°C at hot outlets. Legionella grows best between about 20°C and 45°C, so the idea is to keep water out of that range wherever you can.

It can, which is why buildings with vulnerable users fit thermostatic mixing valves (TMVs) close to outlets. The system stays hot enough to control Legionella, and the TMV blends the water down to a safe temperature at the tap, shower or bath. HSE's HSIS6 says water for whole-body bathing should not exceed 44°C where vulnerable people are at risk. TMVs need regular servicing to keep working, see our TMV servicing page.

At least weekly, which is the standard approach in HSG274 Part 2. Run the outlet long enough to draw fresh water through, and record that it was done. If an outlet is never used, it's usually better to remove it and cut the pipework back so you don't create a dead leg. Our flushing guide explains how to do it without spraying water about.

Quarterly is the usual frequency in HSG274 Part 2, or more often if the risk assessment says so. Scale and biofilm inside shower heads and hoses give bacteria somewhere to live, and showers create the fine spray that carries them into the lungs. In hard water areas, including London and most of the South East, heads scale up quickly, so it's worth keeping on top of it. We can do this as part of a Legionella maintenance contract.

Most commercial buildings need monthly temperature checks on sentinel outlets and water heaters, weekly flushing of little-used outlets, quarterly shower head cleaning and an annual cold water tank inspection. Those frequencies come from HSG274 Part 2, and your written scheme should set the exact list for your building. A typical rented flat needs far less. We can do the checks for you through our maintenance service.

Flush the whole system and check that hot and cold temperatures are back within range before people use it. For longer closures, inspect the cold water tank and consider cleaning, disinfection and sampling. How far you go depends on how long it's been shut and whether anyone kept the water moving in the meantime. Our guide to reopening a building after closure has a step-by-step checklist.

You need sampling when your risk assessment says so, rather than as a routine in every building. It's typical where temperature control is hard to achieve, where users are particularly vulnerable, in healthcare, after disinfection, or when you suspect a problem. Most rented homes and small offices don't need routine sampling. Samples we take are analysed by a UKAS-accredited laboratory. More on our water sampling page.

Results are given in colony-forming units per litre (cfu/L), and HSG274 Part 2 suggests actions at different levels. In broad terms, over 100 cfu/L means control may be slipping and you should resample and review, while over 1,000 cfu/L points to significant colonisation and needs prompt review and remedial action, which may include disinfection. Our article on a positive Legionella sample explains the next steps.

Not on its own. A sample tells you about one outlet at one moment, and Legionella can be present elsewhere in the system or come and go with temperature and use. That's why sampling supports good temperature control, flushing and a current risk assessment rather than replacing them. A clear result alongside good monitoring records is reassuring. A clear result with no records isn't much to go on.

It depends on the size and complexity of the building, so we quote each job rather than publish a price list. A single flat with a combi boiler is a short visit. A care home with tanks, calorifiers and dozens of TMVs takes a lot longer. Tell us what the property is, roughly how many bathrooms or outlets it has and where it is, and we'll come back with a fixed, no-obligation quote.

Yes, we carry out the remedial works ourselves, so you're not left with a report and a list of jobs to farm out. Typical work includes replacing or upgrading cold water tanks, removing dead legs, insulating pipework, adjusting temperatures and disinfecting systems. We price remedials separately and there's no obligation to use us. See our remedial works page.

We're based in Chiswick, west London, and cover the whole UK, with London and the Home Counties as our speciality. That includes Surrey, Kent, Essex, Hertfordshire, Berkshire and Buckinghamshire, and we plan visits further afield so one trip covers as much as possible. Our areas we cover page has notes on each area.

The address or postcode, what the building is and how it's used, and roughly how big it is. Useful extras are whether there's a cold water tank, what heats the hot water, how many bathrooms or outlets there are and whether there are TMVs, showers or anything unusual like a spa pool. If you have an old risk assessment, send it over. Use the quote form or call us on 020 3633 6064.