Do you have hot and cold water systems in your building?
Quick check to see if legionella control applies to you
Why legionella matters
Between 350-400 people are diagnosed with Legionnaires' disease in England and Wales each year. Around 10-15% of cases are fatal. Many outbreaks are linked to poorly maintained water systems in hotels, care homes, hospitals, and commercial premises.
The law is clear: if you are an employer, landlord, or have control over premises, you must identify and assess sources of legionella risk and prevent or control the risk.
Under the Health and Safety at Work Act 1974 and the Control of Substances Hazardous to Health Regulations 2002 (COSHH), duty holders must assess the risk of legionella exposure and implement a written scheme of control. HSE's Approved Code of Practice L8 provides the authoritative guidance.
What is Legionella?
Legionella is a bacterium found naturally in water sources. It becomes a hazard when:
- It grows and multiplies in water systems (typically between 20°C and 45°C)
- Water droplets (aerosols) containing the bacteria are created and dispersed
- People breathe in contaminated aerosols
Legionnaires' disease
The most serious infection caused by legionella bacteria. Symptoms include:
- High fever and chills
- Cough (may be dry or produce phlegm)
- Shortness of breath
- Muscle aches and headache
- Confusion and delirium in severe cases
Legionnaires' disease is a form of pneumonia. It requires hospital treatment and can be fatal, particularly for vulnerable groups: the elderly, smokers, people with weakened immune systems, and those with chronic respiratory or kidney disease.
Legionella cannot be passed from person to person. Infection occurs by breathing in tiny water droplets containing the bacteria. This is why showers, cooling towers, spa pools, and fountains are common sources of outbreaks.
Who is responsible?
If you have control over premises with water systems, legionella control is likely your legal duty. This includes:
- Employers — responsible for employees and anyone affected by your business activities
- Landlords — responsible for water systems they own or control, including common areas and shared water systems in HMOs and blocks of flats
- Property managers — if you have day-to-day control of water systems
- Care home operators — particularly important due to vulnerable occupants
- Hotel and hospitality operators — showers, spa facilities, and cooling systems
- Healthcare providers — hospitals, clinics, dental practices with dental unit water lines
- Building owners and occupiers — through ownership, lease, or maintenance agreements
The duty holder is whoever has control of the premises and the water systems. In shared buildings, there may be multiple duty holders who must cooperate.
Legionella control by sector
Different premises face different legionella risks:
| Sector | Key Risks | Priority Actions |
|---|---|---|
| Offices | Hot/cold water systems, infrequently used outlets, showers | Temperature monitoring, outlet flushing, quarterly checks |
| Care Homes | Vulnerable occupants, multiple showers, large hot water systems | Full risk assessment, detailed written scheme, professional support essential |
| Hotels & B&Bs | Showers, spa facilities, cooling towers, variable occupancy | Weekly temperature checks, pre-let flushing, cooling tower regime |
| Hospitals & Healthcare | Immunocompromised patients, dental water lines, complex systems | Stringent controls, water quality testing, professional water safety group |
| Landlords (HMOs) | Shared bathrooms, communal systems, tenant turnover | Temperature checks, shower head descaling, tenant briefing |
| Landlords (Flats) | Communal hot/cold water systems, individual dwellings | Assess communal systems, TMV maintenance, tenant cooperation |
| Leisure Centres | Showers, spa pools, cooling towers, high aerosol risk | Daily/weekly monitoring, chemical treatment, professional maintenance |
| Industrial Sites | Cooling towers, evaporative condensers, process water systems | Monthly inspections, biocide treatment, quarterly testing, L8 notification |
This is general guidance. Your specific premises requires a tailored risk assessment.
The key legislation
Health and Safety at Work Act 1974
Places a general duty on employers and those in control of premises to ensure, so far as reasonably practicable, the health, safety, and welfare of employees and others who may be affected.
Control of Substances Hazardous to Health Regulations 2002 (COSHH)
Require duty holders to prevent or control exposure to hazardous substances, including biological agents like legionella.
HSE Approved Code of Practice L8 (ACOP L8)
"Legionnaires' disease: The control of legionella bacteria in water systems"
This is the authoritative guidance document. Following the ACOP gives you a strong defence in law. It sets out:
- Who is responsible
- How to assess risk
- How to manage and control risk
- Competence requirements
- Record keeping
ACOP L8 has special legal status. If you're prosecuted for a breach of health and safety law, and it's proven you didn't follow the relevant provisions of the ACOP, you'll need to show you complied with the law in some other way — or a court will find you at fault.
HSG274 Parts 1, 2, and 3
Technical guidance supporting ACOP L8:
- Part 1: Evaporative cooling systems (cooling towers)
- Part 2: Hot and cold water systems
- Part 3: Other risk systems (spa pools, fountains, water features, etc.)
Legionella risk assessment
Every duty holder must conduct a suitable and sufficient legionella risk assessment. This involves:
1. Identify hazards
- Water systems and services: hot and cold water, cooling towers, spa pools, water features
- Water temperatures — is water stored or distributed in the 20-45°C range?
- Water stagnation — are there dead legs, infrequently used outlets, or little-used buildings?
- Aerosol creation — showers, taps, spray taps, cooling towers, fountains
- Water quality — scale, rust, organic matter that bacteria feed on
2. Identify people at risk
- Who uses the building? Employees, residents, visitors, vulnerable groups?
- Are there people particularly susceptible? Elderly, smokers, immunocompromised, chronic respiratory conditions?
3. Assess current controls
- What measures are already in place?
- Are they adequate to control the identified risks?
- Temperature monitoring regimes?
- Cleaning and descaling schedules?
- Water treatment programmes?
4. Record findings
- Significant findings must be recorded
- Identify what further action is needed
- Prioritise actions based on risk
5. Implement control measures
Create a written scheme of control (see below) and implement it.
6. Review regularly
- At least every 2 years (more frequently if circumstances change)
- After significant changes to the system or use of the building
- Following a suspected legionella incident
Should you DIY or hire a professional?
Do It Yourself
- •Small, simple water systems
- •Low-risk premises (small offices, shops)
- •No vulnerable occupants
- •You or staff member is competent (trained)
- •Time to conduct monthly/quarterly tasks
- •Cost: Free (plus training)
Hire a Professional
Recommended- •Complex or large water systems
- •Cooling towers or spa pools
- •Care homes, hospitals, hotels
- •Vulnerable occupants present
- •No in-house competence
- •Cost: £300-1,500+
Bottom line: For simple, low-risk systems, you can conduct risk assessments yourself if you're competent. For anything involving sleeping accommodation, vulnerable people, cooling towers, or complex systems, professional assessment is strongly recommended.
You must be "competent" to carry out legionella risk assessments. Competence means having the necessary training, skills, knowledge, and experience. For complex systems, this typically means hiring a specialist legionella assessor.
Written scheme of control
Once you've identified risks, you must prepare a written scheme setting out how you will manage and control those risks. This should include:
System details
- Schematic drawings or descriptions of the water system
- Location of key components: tanks, calorifiers, TMVs, deadlegs, sentinel outlets
- Roles and responsibilities — who does what
Control measures
- Temperature controls: cold water stored below 20°C, hot water stored at 60°C and distributed at 50°C+
- Outlet management: flushing regimes for infrequently used outlets
- Cleaning and disinfection schedules for tanks, showerheads, TMVs
- Water treatment programmes (if applicable)
Monitoring arrangements
- Temperature monitoring schedules (usually monthly at sentinel outlets)
- Inspection schedules (visual checks, cleaning)
- Sampling and testing (if risk assessment requires it)
Remedial actions
- What to do if temperatures are out of range
- Escalation procedures
- Emergency actions
Record keeping
- All monitoring records, test results, maintenance activities
- Training records for those responsible
- Review dates
The written scheme must be followed and kept up to date. It's not a tick-box exercise — it's your plan to keep people safe. Inspectors and courts will ask to see it if something goes wrong.
Temperature monitoring
Temperature control is the primary defence against legionella growth:
At calorifier outlet (60°C+) and sentinel taps (50°C+ within 1 minute)
At storage tank outlet (<20°C) and sentinel taps (<20°C after running)
Rotate through all outlets over the year
Flush infrequently used outlets (e.g. vacant rooms, guest toilets)
Clean, descale, and check thermostatic mixing valves
Descale and disinfect shower heads and hoses
Inspect and clean cold water storage tanks
Review written scheme and update risk assessment if needed
Critical temperatures:
- Cold water must be stored and distributed below 20°C
- Hot water must be stored at 60°C (kills legionella) and distributed so it reaches outlets at 50°C or above within 1 minute
If you can't achieve these temperatures, you need additional controls (such as chemical treatment or increased monitoring).
Landlord responsibilities
If you're a landlord, your duties depend on the type of property:
HMOs and blocks of flats with communal systems
You are responsible for shared water systems. You must:
- Conduct a legionella risk assessment of communal hot and cold water systems
- Implement a written scheme of control
- Monitor temperatures and maintain systems
- Keep records
- Provide information to tenants (e.g., advising them to run taps/showers if away for extended periods)
Single dwelling lets
Generally, domestic premises occupied by a single household are not covered by ACOP L8 (as they're not workplaces or premises controlled by business). However:
- If you employ cleaners, tradespeople, or managing agents who enter the property, you may have duties to them
- You still have general landlord duties to maintain water systems in good repair
- Best practice is to check systems before new tenancies and advise tenants on water safety
Practical tip for landlords: Before a new tenancy, run all taps and showers for several minutes to flush through stagnant water. Advise tenants to do the same if the property is left vacant for more than a week.
Cooling towers and evaporative condensers
If you have a cooling tower or evaporative condenser, you must:
- Notify the local authority within 1 month of commissioning
- Conduct a full risk assessment (professional required)
- Implement a detailed written scheme (daily, weekly, monthly tasks)
- Conduct quarterly microbiological testing
- Keep comprehensive records
Cooling towers are high-risk systems and are a common source of outbreaks. Professional management is essential.
Common questions
Yes, if you have employees or others who may be exposed to water systems. Even small offices need a risk assessment. However, for simple systems with no identified risks (e.g., mains-fed cold water, instant hot water heaters, no showers), the assessment may be straightforward and the ongoing controls minimal.
For most systems, monthly temperature checks at sentinel outlets (the furthest and closest points, plus calorifier/tank outlets) are recommended. Some higher-risk premises may need weekly checks. HSG274 Part 2 provides detailed schedules. You should rotate through all outlets quarterly or annually depending on the system.
Sentinel outlets are representative taps or showers used for monitoring. Typically: the outlet closest to the hot water source, the furthest outlet, the first outlet on a return loop, and outlets on priority areas (e.g., clinical areas). Checking these gives you a picture of the whole system's performance.
You can if you're competent. For simple, low-risk systems, competence can be gained through training courses (e.g., Legionella Awareness, City & Guilds qualifications). For complex systems, cooling towers, healthcare, or care homes, you should use a professional legionella specialist. HSE expects duty holders to demonstrate competence.
Not always. For most domestic-style hot and cold water systems, temperature control and routine maintenance are sufficient. Water sampling may be required for cooling towers (quarterly), complex systems, or where the risk assessment identifies it as necessary. It can also be useful to verify control measures are working. Sampling must be done by accredited labs.
Legionella bacteria are killed at 60°C and above. At 60°C, they die within 2 minutes. This is why hot water should be stored at a minimum of 60°C. At 50°C, legionella can survive but won't multiply effectively. Between 20-45°C is the ideal growth range. Below 20°C, legionella lies dormant but doesn't multiply significantly.
It depends. For HMOs and blocks of flats with communal water systems (shared tanks, pipework), yes — landlords must assess and control legionella risk. For standard single-dwelling lets, ACOP L8 doesn't typically apply as they're domestic premises, but landlords still have duties under general health and safety law if they employ contractors who may be exposed, and best practice is to check systems between tenancies.
Breaches of health and safety law can result in unlimited fines and up to 2 years imprisonment for serious failures. HSE and local authorities can issue improvement or prohibition notices. Following a legionella outbreak, corporate manslaughter charges are possible if death results from gross negligence. Even without an outbreak, failure to assess and control risk can be prosecuted.
Immediately notify the relevant enforcing authority (HSE or local authority) and public health authorities. Cooperate fully with the outbreak investigation. Do not alter the water system until investigators have assessed it. Provide all risk assessment and monitoring records. Seek specialist advice. Early cooperation and transparency are critical.
HSE recommends keeping records for at least 5 years. However, because legionella cases can take time to identify and prosecutions can occur years later, best practice is to keep records indefinitely or for as long as you control the premises. Records include risk assessments, written schemes, temperature logs, maintenance records, training records, and any test results.
Real enforcement examples
Hotel fined £750,000 after guest death from Legionnaires' disease
A hotel guest died from Legionnaires' disease. HSE investigation found systemic failures in water safety management.
- ✗No legionella risk assessment had been conducted
- ✗No written scheme of control in place
- ✗No temperature monitoring or records
- ✗Infrequently used rooms and outlets not flushed
- ✗Hot water temperatures found below 50°C in many outlets
- ✗No trained responsible person for water safety
The hotel operator was fined £750,000 plus £77,000 costs. The company was also required to undertake a full system remediation and implement ongoing professional water safety management.
Legionella control is not optional. The consequences of neglect can be fatal. Courts take a very serious view of failures that lead to death. Even without a fatality, systemic failures to assess and control risk can result in six-figure fines.
Source: Based on HSE prosecution records
Care home prosecuted after inadequate legionella controls
A care home was prosecuted following an HSE inspection that revealed serious deficiencies in legionella management, despite no outbreak having occurred.
- ✗Risk assessment was over 3 years old and inadequate
- ✗No evidence of temperature monitoring
- ✗Dead-legs identified but not removed or managed
- ✗Staff had no legionella awareness training
- ✗Written scheme existed but was not being followed
The care home operator was fined £120,000 plus costs. An improvement notice required immediate remedial action and professional legionella management to be put in place.
You don't need an outbreak to be prosecuted. HSE and local authorities conduct proactive inspections. Care settings are high-risk due to vulnerable occupants. Having a written scheme is not enough — you must actually implement it and demonstrate ongoing compliance.
Source: Based on HSE prosecution records
Manufacturing company fined after failing to manage cooling tower
A manufacturing company failed to properly manage its cooling tower, leading to an outbreak investigation and prosecution.
- ✗Cooling tower not notified to the local authority
- ✗Inadequate biocide treatment and monitoring
- ✗Quarterly water testing not conducted
- ✗No competent person managing the system
- ✗Records incomplete and inconsistent
The company was fined £200,000 plus costs. A prohibition notice was served preventing use of the cooling tower until a compliant management regime was implemented.
Cooling towers are high-risk and heavily regulated. Notification, quarterly testing, and daily/weekly monitoring are legal requirements, not optional. Duty holders must ensure competent management — if you don't have in-house expertise, you must contract it.
Source: Based on HSE prosecution records
Related sectors
Legionella control applies across many sectors. Select your sector for tailored considerations:
Care Homes
Vulnerable residents mean stringent controls and professional water safety management are essential.
Landlords
Understand your duties for HMOs, blocks of flats, and single-dwelling lets.
Hospitality
Hotels, B&Bs, gyms, and spas face high risk from showers and spa facilities.
Healthcare
Hospitals and clinics require rigorous water safety protocols to protect immunocompromised patients.
Related content
- Water temperature monitoring guide — How to monitor hot and cold water temperatures effectively
- Legionella risk assessment guide — Understanding what's involved in a risk assessment
- Do I need a legionella assessment? — Check if legionella controls apply to you
- Legionella testing guide — When and how to test water for legionella
- Landlord's guide to legionella — Specific guidance for residential landlords
Need professional help with legionella control? A qualified water safety specialist can conduct risk assessments, prepare written schemes, and provide ongoing monitoring and support tailored to your premises.
Disclaimer: This guidance is for general information only and does not constitute legal or professional advice. Legionella control requirements depend on your specific circumstances. For complex systems or high-risk premises, you should seek professional advice from a competent legionella specialist. While we aim to keep this guidance up to date, regulations and best practices may change. Always refer to the latest HSE guidance (ACOP L8 and HSG274) and consult your enforcing authority if in doubt.