Legionella Guidance

Legionnaires’ disease is a potentially severe but uncommon form of pneumonia associated with exposure to water systems (natural or man-made) colonised by legionella bacteria – generally only of danger to elderly people and the sick. Being a notifiable disease, all outbreaks are reported in national statistics. In an average year, there are some 300-400 reported cases, of which less than 8% are fatal – mainly in older people.

The Health and Safety Executive (HSE) published a revised approved Code of Practice (AcoP) on ‘Legionnaires’ Disease – The control of legionella bacteria in water systems’ in 2009 (further revised in 2013) for employers and those with responsibilities for the control of premises, including landlords. Whilst HSE’s interpretation of the law has not changed, their guidance was revised. The scope of the ACoP previously applied to hot water systems which had capacities of 300 litres or over (an arbitrary limit designed to exclude domestic system) but in the recently revised guidance HSE specifically consider the case of private sector residential landlords and the duties that HSE believes will apply.

Landlord’s Duties

Residential landlords have duties to ensure that their premises are safe and free from hazards, and many of these areas such as gas safety and the Housing Health and Safety Rating System (HHSRS) have specific legislation and are well documented. However, there is no specific legislation relating to Legionella aimed at residential property and the legal case for carrying out detailed risk assessments in the domestic property environment is not clear. The HSE maintains that every landlord has a legal duty to undertake Legionella checks under the Health and Safety at Work Act 1974, and also under secondary legislation such as the Control of Hazardous Substances Hazardous to Health Regulations 2002 (COSHH).

The property condition and safety duties under the Housing Act 2004 are clearer and apply specifically to landlords. This Act makes provision for the Housing Health and Safety Rating System and places an implied duty on the landlord of residential premises to keep the property free from known types of hazards.


There is no provision in the Act or the related regulations specifically for Legionella but a landlord has a duty to keep the property free from these types of hazards, or advise the tenant how this may be done. Under HHSRS, a local authority has the option of issuing a hazard awareness notice, an improvement notice or a closure order.

According to the HSE guidance, the law requires simple, proportionate and practical actions to be taken including identifying and assessing sources of risk, managing the risk, preventing or controlling the risk and periodically checking that any control measures are effective. All water systems require a risk assessment, but not all systems require elaborate control measures. The guidance acknowledges that a risk assessment in most residential settings may show the risks are low, in which case no further action may be necessary.

Smaller Premises

The HSE advice for smaller premises relates to ‘smaller buildings with less complex hot and cold water systems such as residential accommodation and housing associations.’ The HSE state that an employer or someone in control of premises, including landlords have a responsibility to:

  • Undertake the duties in ‘what you must do’ to ensure that the risk from exposure to Legionella in the property is property controlled;
  • Carry out a risk assessment – see example HSE risk assessment for a block of flats which includes a
    section on legionella;
  • Review the risk assessment if there are significant changes e.g. expansion of water system, changes
    in resident population etc;
  • Consider the susceptibility of staff and those more at risk of infection due to age, illness etc.

Do I need to pay for a Professional Risk Assessment?

Any Legionella risk assessment and related measures should be proportionate to the level of risk – which for the majority of hot and cold water supply systems in residential property is generally low. Because of this, the HSE acknowledge the competent landlord may carry out the risk assessment themselves – There is no legal requirement to employ a professional consultant to do the assessment. The HSE guidance (HSG274 – Control of Legionella bacteria in hot and cold water systems - available online) explains how this risk assessment may be carried out. These include checking the following:

  • Are conditions right for bacteria to flourish e.g. is the temperature of the water between 20 degrees
    Celsius and 45 degrees Celsius?
  • Are there any areas of stagnant water or infrequently used outlets etc?
  • Is there any redundant pipe work?
  • Is there any debris in the system such as rust, sludge, scale etc?
  • Are there any employees, residents etc who are vulnerable to infection such as the elderly?

In most residential lettings the answer to the above questions will be no in which case the risk will be low and no further action will be necessary e.g. housing units with small domestic-type water systems where water turnover is high. Where a risk is identified the HSE provide advice on simple control measures to help manage the risk of exposure to legionella. The HSE suggest flushing out the system before letting the property, advising tenants on control of legionella (e.g. flushing out showers when away from the property for a period of time), avoid debris getting into the system (e.g. ensure cold water tanks, where fitted, have a tight-fitting lid), ensuring any redundant pipe work is identified and removed, setting control parameters (thermostatic mixer valves should be fitted as close as possible to outlets, where a scald risk is identified) and checking temperature of the water.

The HSE advise to review the assessment periodically in case anything changes in the system. However, the frequency of inspection and maintenance will depend on the system and the risks it presents but for most residential lettings a simple assessment when carrying out other routine inspections will suffice. Legionnaires’ disease: Part 2: The control of Legionella bacteria in hot and cold water systems published by the HSE in 2014 gives further guidance for landlords on how to manage your duty in shared premises and residential accommodation (Pages 45 to 47).