Legionella FAQ

Legionella Frequently Asked Questions | Legionella Questions | Risk Assessment Support

When and how often do I need a legionella risk assessment?


The Approved Code of Practice L8 (HSG 274) in accordance with The Health & Safety at Work Act 1974 states that – “The Duty holder should arrange to review the assessment regularly and specifically when there is reason to suspect it is no longer valid. An indication of when to review the assessment and what to consider should be recorded and this may result from:

  • A change to the water system;
  • A change to the use of the building where the system is installed;
  • New information available about risks or control measures;
  • The results of checks indicating that control measures are no longer effective;
  • Changes to key personnel;
  • A case of legionnaires disease.”

Here at uRisk we recommend annual reviews to ensure correct implementation is being carried out. Legionella bacteria can double within 15 minutes, so it is important to review your risk assessment and monitoring records regularly.


Why do I need a legionella risk assessment?


HSG 274 Part 2 (Paragraph 2.122 – Pages 40-41)

In both hot and cold water systems, samples should be taken:

• if considered necessary by the risk assessment;

• from areas where the target control parameters are not met (i.e. where disinfectant levels are low or where temperatures are below 50°C (55°C in healthcare premises) for HWS or exceed 20°C for cold water systems);

• from areas subject to low usage, stagnation, excess storage capacity, dead legs, excessive heat loss, cross flow from water system or other anomaly.

In cold water systems, samples should also be taken as required:

• from the point of entry (or nearest outlet) if the water is supplied from a private water supply or where the temperature of the incoming mains supply is above 20°C from the cold water storage tank or tanks;

• from the furthest and nearest outlet on each branch of the system (far and near sentinel outlets).

In hot water systems, samples should be taken as required:

• from the calorifier hot water outlet and from the base of the calorifier, if it is safe to do so, as some systems are under considerable pressure;

• from the furthest and nearest outlet on each branch of a single pipe system (far and near sentinel outlets);

• from the furthest and nearest outlet on each loop of a circulating system (far and near sentinel outlets).

Frequency – There are no current guidelines on frequency of sampling other than actioning sampling.

Routine sampling from sentinel points will aid water analysis and confirm monitoring is sufficient.

Please refer to the HSG 274, HTMs, and manufacturers guidelines for sampling frequency.

What to do if I get a Legionella positive sample?



• if the minority of samples are positive, the system should be resampled, if similar results are found again, a review of the control measures and risk assessment should be carried out to identify any remedial actions necessary or

• if the majority of samples are positive, the system may be colonised, albeit at a low level. An immediate review of the control measures and risk assessment should be carried out to identify any other remedial action required. Disinfection of the system should be considered.

>1000 cfu/l

The system should be resampled and an immediate review of the control measures and risk assessment carried out to identify any remedial actions, including possible disinfection of the system. Retesting should take place a few days after disinfection and at frequent intervals afterwards until a satisfactory level of control is achieved.

What monitoring must I do for Legionella?


‘Section 4: Water Logbook’ of this report identifies your site specific monitoring requirements.

However, for periodic maintenance and monitoring duties you must carry out, directly quoted from various HSE and other guidelines as specified, or as indicated by the risk assessment – “You must keep records of these actions in your logbook”.

HSG 274 Part 2 (Table 2.1: Checklist for hot and cold-water systems – Pages 31-33)

What are the Thermostatic Valve (TMV) temperature requirements?


HTM 04-01: Safe water in healthcare premises. Part A: Design, installation and commissioning practices (Table 2 – Page 55)

Areas where TMV type 3 valves should be fitted:

• Showers and hair-wash facilities (set to 41°C)

• Unassisted Baths (set to 41°C)

• Baths for Assisted Bathing (set to 46°C – to allow for the cold mass of the bath. NB – prior to patient immersion, water should be checked with a thermometer.)

• Bidets (set to 38°C)


When is a chlorination/disinfection required?


HSG 274 Part 2 (Paragraph 2.127 – Page 42)

Where necessary, hot and cold water services should be cleaned, flushed and disinfected in the following situations, as specified in BS 8558:

• on completion of a new water installation or refurbishment of a hot and cold water system;

• on installation of new components, especially those which have been pressure tested using water by the manufacturer (see the manufacturer’s instructions);

• where the hot and cold water is not used for a prolonged period and has not been flushed as recommended or the control measures have not been effective for a prolonged period. For example, this could be as little as two or three weeks, but will depend on the ambient temperature, condition of the water system, potential for exposure to aerosols and the susceptibility of users considered in a specific risk assessment;

• on routine inspection of the water storage tanks, where there is evidence of significant contamination or stagnation;

• if the system or part of it has been substantially altered or entered for maintenance purposes that may introduce contamination;

• following water sampling results that indicate evidence of microbial contamination of the water system (see Table 2.2 or 2.3);

• during, or following an outbreak or suspected outbreak of legionellosis linked to the system;

• or where indicated by the risk assessment.

How to comply with Legionella requirements?


As an employer, or a person in control of the premises, you are responsible for health and safety and need to take the right precautions to reduce the risks of exposure to legionella. You must understand how to:

• identify and assess sources of risk

• manage any risks

• prevent or control any risks

• keep and maintain the correct records and carry out any other duties you may have


Do we need training for Legionella?


“The responsible person(s) appointed to implement the control measures and strategies should be suitably informed, instructed, and trained and their suitability assessed.”

Section 18 – ACOP L8 HSG 274 Part 2 (Fourth Edition 2014)

What are the Water Supply (Water Fittings) Regulations 1999


These regulations are not directly concerned with legionella hazards, but govern the design, construction and use of materials in water systems. They cover:

• backflow protection (use of air gaps and non-return valves);

• the maintenance of water quality (tank designs);

• the use of materials (those that do not promote bacterial growth);

• water conservation (prevent leakage).

Must I improve access to water fittings?


ACOPs L8 states that “It is important that there should be ease of access to all parts of the system, components and associated equipment for management and maintenance purposes, e.g. tanks, calorifiers, thermostatic mixing valves (TMVs)…”

For more information please visit HSEs website for more information about ACOP L8.

Do I need to remove or replace Flexible Hoses?


You should ensure all flexible hoses comply with the WRAS approval scheme and be tested and comply with BS 6920. “In buildings where there are those with an increased susceptibility to infection or with processes requiring specific water characteristics, materials of an enhanced quality may be required.

Healthcare buildings and care homes should specifically take note of alerts and advice from the Department of Health and Health Facilities Scotland. For example, healthcare premises are advised against the use of ethylene propylene diene monomer (EPDM) lined flexible hoses (tails) as these have been shown to be a risk of microbial colonisation. Such flexible connections should therefore only be used in healthcare premises where an installation has to move during operation or is subject to vibration.”

HSE 274 Part 2 p.2.35

“Flexible hoses should be used only for the following applications: to allow for vibration of equipment; to accommodate vertical displacement of high and low baths and sinks; to facilitate essential maintenance and access of bespoke equipment when no alternative is available. Note – Where fitted, flexible hoses should be kept as short as possible and be kink-free as to no affect flow”. – The Health Technical Memorandum 04-01: Safe water in healthcare premises. Part A: Design, installation and commissioning states in p.3.41

Caution Hot Water Signs, Not Drinking Water, Drinking Water Signs


“The Regulations require employers to use a safety sign where there is a significant risk to health and safety” – The Health & Safety (Safety Signs and Signals) Regulations 1996 p.4

Caution signs are recommended at any location where there is the potential for scalding hot water. This includes where TMVs are located as they may fail.

Download the HSE Legionella Guidelines here for FREE


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Extremely happy with our legionella risk assessment carried out by uRisk, easy to understand and great customer service. Thanks again
Nickayla Robertson
Nickayla Robertson
21:22 15 Jan 19
Brilliant service! Thanks a lot for the hard graft
Leon Macauley
Leon Macauley
21:12 15 Jan 19
Brilliant Service, efficient, professional, punctual and friendly.
Alex Windsor
Alex Windsor
18:21 15 Jan 19
uRisk have been helping us with our Legionella Control for a number of years now. We've recently had a CQC audit and they were very impressed with our legionella compliance! Thank you for all your help.
Mike Port
Mike Port
20:41 07 Aug 18
Fantastic training courses and we've found the legionella risk assessment very easy to read and far more detailed than any we have previously had. 5 star service!
Gemma Pond
Gemma Pond
20:37 07 Aug 18
Incredibly detailed and professional team. Have been beyond helpful with with our CQC legionella compliance for our Safety. They’ve found solutions to fit around how we work and our budgets. We are always advised with reference to HSE which has been brilliant.
Amy Thorne
Amy Thorne
20:29 07 Aug 18
We're a small GP practice and started using uRisk for legionella risk assessments. We opted to use their remedial and monitoring services and they've been absolutely great. We cannot recommend them enough! Thank you so much!
Amanda Pates
Amanda Pates
18:30 07 Aug 18