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Legionella Risk Assessment

Legionnaires’ disease is a potentially fatal form of pneumonia caused by the inhalation of small droplets of contaminated water containing Legionella. All man-made hot and cold-water systems are likely to provide an environment where Legionella can grow, especially where conditions are favourable such as suitable growth temperature (between 20°C – 50°C) where water droplets (aerosols) are produced and dispersed, where water is stored and/or recirculated, where water is left to stagnate over time, and where nutrients or ‘food’ are present for the organism to grow such as rust, sludge, scale, biofilmetc) all of which could cause the bacteria to multiply thus increasing the risk of exposure

The Legionella bacteria requires specific temperature conditions to multiply.  Significant growth of the bacteria occurs in the range of 35°C to 40°C and its optimum temperature is 37°C.  At low temperatures it remains dormant, and at temperatures exceeding 50°C it begins to die off.  At 60°C 90% of the bacteria is killed within 2 minutes; this is the optimum temperature at which water should be heated and stored to ensure risks are mitigated


Certain groups of people are at a higher risk of contracting Legionnaire’s Disease than others, including new-born babies and people over 45 years of age, smokers, and heavy drinkers, those with chronic respiratory or kidney diseases, diabetics, lung and heart disease sufferers, and anyone with a suppressed immune system

The Landlord’s Duties

Landlords have a duty to assess the risk from exposure to legionella to ensure the safety of their tenants, a simple assessment may show that there are no real risks and are being properly managed by the duty holder, along with implementing simple, proportionate, and appropriate control measures. For most domestic hot and cold-water systems, appropriate water temperature is the most reliable way of ensuring the risk of exposure to Legionella bacteria is minimised i.e., keep the hot water hot, cold water cold and not least, keep it moving


The Tenant’s Duties

Tenants have an active part to play in ensuring the water system is effectively managed; tenants are referred to as, “The Responsible Persons”

One of the key responsibilities a responsible person has as a user of the water system is to keep outlets clean, and to keep water moving – when water stands still it warms up and starts to stagnate, this is when legionella and other bacteria start to multiply, unclean outlets provide a food source.  This life cycle can be avoided by actively practising the guidance set out within this written control scheme

As trained, competent and fully insured Legionella Risk Assessors, we provide an ACOP L8 compliant risk assessment document following a site visit to assess the system

Please find a download to our legionella risk assessment literature:



- Mutually convenient site visit appointment taking approx 45 minutes to data collect relevant information

- A report on the adequacy of the water tanks and tank’s seals and any recommendations to lower any risk               identified

- Record temperatures at each outlet to assess the risk of these outlets incubating the legionella bacteria

- Identify any dead legs in the system and associated recommendations

- Produce a simple, proportionate, and appropriate documented plan of control measures outlining the duty              holder’s responsibilities following the site visit

- Produce a documented plan to be passed on to your tenants of the control measures in place, and what their        responsibilities are as responsible persons within the documented management plan

- Discount for floorplan / EPC / Inventory / Check-Out within the same instruction

- Key collection and drop off to the responsible person / agent if required

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