Legionella Risks Explained
If you’re looking for the facts, confirmation that the information you have been given is accurate, then you’re at the right please. Here we break down the guidance given by the HSE to make it easier to digest.
Control and Management
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Duty holder should arrange to review the assessment regularly and specifically when there is reason to suspect it is no longer valid.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. Changes in water quality, such as unusual taste, odor, or discoloration, may serve as a not drinking water sign, signaling potential issues with the pump that require servicing.
Water Sampling Analysis Recommended
“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, from areas subject to low usage, stagnation excess storage capacity, dead legs, excessive heat loss, cross flow from water systems or other anomaly” – HSG 274 part 2 p.2.122 See when to sample from HSG 274 part 2.
Water Logbook
“Records kept for monitoring and inspection, which should be kept for at least five years.” – HSG 274 part 2 p.25
Record Keeping
“Records kept for monitoring and inspection, which should be kept for at least five years.” – HSG 274 part 2 p.25
Legionella Awareness Training
“Inadequate management, lack of training and poor communication can be contributory factors in outbreaks of legionnaires’ disease.” – HSG 274 part 2 p.16
Site Restrictions
“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., tank, calorifiers, thermostatic mixing valves (TMVs), blending valves, circulation pumps etc.” – HSG 274 part 2 p2.34
Cold Water Storage Tanks
Clean and/or disinfection tanks
“The cold water storage tank should be cleaned, disinfect and any faults rectified”. – HSG 274 part 2 p.2.57
Tank refurbishment required
Remove tank(s) where possible due to insufficient turnover and convert to mains water supply or remove existing tank(s) and replace with a new tank (with correct fittings)
Tank secure base
The tank is sitting on an un-secure base which should be suitable for the tank to rest on.
Tank circulation
“Inlet and outlet on opposite sides of the cold water tank to encourage water flow across the tank and avoid low flow areas within the tank” – HSG 274 part 2 figure 2.4
Tank close fitting lid
“The lid should be closely fitted and in good conditions”. – HSG 274 part 2 p.2.57
Tank insulation
“The thermal insulation should be in good condition so that it protects from extremes of temperature.” – HSG 274 part 2 p.2.57
Tank pipe insulation
“Thermal gain should be kept to a minimum by adequate lagging and separation of cold water services pipework and components from hot water services and heating systems” – HSG 274 part 2 p.2.36 point 5
Tank suitable overflow size
Overflow size is not twice the size of the inlet. May not remove water quick enough should the ball valve fail should the inlet be of an equivalent size or smaller.
Tank air vent with screen
“The insect and vermin screen on the overflow and warning pipes and any vents should be intact and in good condition” – HSG 274 part 2 p.2.57
Tank overflow screen
“The insect and vermin screen on the overflow and warning pipes and any vents should be intact and in good condition”
– HSG 274 part 2 p.2.57
Tank vent pipe less than 25mm air gap
“The open vent pipe from the calorifier should be sufficiently raised above the water level” – HSG 274 part 2 p.2.37
Divert vent pipe to tundish
“The open vent pipe from the calorifier should be sufficiently raised above the water level” – HSG 274 part 2 p.2.37
Support tank struts internally hollow
Hollow struts (roof supports) may provide legionella proliferation conditions and should be replaced with solid struts
Tank capacity not suitable for use
The hot water source is not a suitable capacity for use. Temperatures appear to fluctuate in and out of compliant ranges due to low storage volume.
Expansion Vessels
Expansion vessel – installed on cold flowing pipes
“To minimise the risk of microbial growth, expansion vessels should be installed: in cool areas on cold flowing pipes” – HSG 274 part 2 p2.39
Expansion vessel – mounted closely to incoming water supply
“To minimise the risk of microbial growth, expansion vessels should be installed: mounted as close to the incoming water supply as possible” – HSG 274 part 2 p2.39
Expansion vessel – mounted vertically
“To minimise the risk of microbial growth, expansion vessels should be installed: mounted vertically on pipework to minimise any trapping of debris” – HSG 274 part 2 p2.39
Expansion vessel – installed with isolation and drain valve
“To minimise the risk of microbial growth, expansion vessels should be installed: with an isolation and drain valve to aid flushing and sampling” – HSG 274 part 2 p2.39
Pipework
Dead legs/ends
Cut back redundant pipe work to avoid stagnation.
The Water Regulations Advisory Scheme advises that ‘Minimising this risk can be achieved by completely removing redundant pipe work. Where this is not practicable the pipe should be terminated so that any ‘dead leg’ so created is no longer than twice the diameter of the pipe’. For example:
- 15mm to be no longer than 30mm (just over 1”)
- 22mm to be no longer than 44mm (just under 2”)
- 28mm to be no longer than 56mm (just over 2”)
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
Isolation valves
“Isolation valves should be included in all locations to facilitate maintenance and the implementation of control measures” – HSG 274 part 2 p2.34
Lead pipework
Galvanised/lead pipe work is recommended to be removed as it may lead to legionella proliferation. “Avoid using materials that harbour bacteria and other microorganisms or provide nutrients for microbial growth”. – HSG 274 part 2 p.23
Backflow protection
“Single check valves are commonly used to prevent backflow” – HSG 274 part 2 p.2.32
Signs
Asset labelling
“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. tank, calorifiers, thermostatic mixing valves (TMVs), blending valves, circulation pumps etc.” – HSG 274 part 2 p2.34
Caution hot water, 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.
Monthly temperature point signs
“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. tank, calorifiers, thermostatic mixing valves (TMVs), blending valves, circulation pumps etc.” – HSG 274 part 2 p2.34
Heat Sources
Heater faults
Repair broken water heaters that are intended to be brought back into use.
Heat source timer
“During periods of low usage such as overnight or at weekends, fitting a timer which switches off the immersion heater may prove effective. The timer should be set to switch the immersion heater on again in time to ensure the water is heated sufficiently to achieve microbial control before use” – HSG 274 part 2 p.2.13
Temperature gauge fitted
Fit a hot water cylinder gauge to the flow/ return of the hot water cylinder.
Temperature adjustment
“Hot water should be stored at least at 60°C and distributed so that it reaches a temperature of 50°C (55°C in healthcare premises) within one minute at the outlets” – HSG 274 part 2 p.2.6
Purge any debris in base of HWC
Repair broken water heaters that are intended to be brought back into use.
Drain, isolate, remove hot water heaters
“Consideration should be given to removing infrequently used showers, taps and any associated equipment that users water” – HSG 274 part 2 table 2.1
Pump required (to aid system circulation)
Pump required on the hot water cylinder to aid circulation and improve hot water outlet temperatures.
Destratification pump (for large HWC)
“Stratification, which may occur in large calorifiers, should be avoided and fitting a timer-controlled shunt pump to circulate the water from the top of the calorifier to the base during the period of least demand should be considered” – HSG 274 part 2 p.2.25
Return pipe check valve (back flow protection)
“Single check valves are commonly used to prevent back flow of hot water to the cold feed” – HSG 274 part 2 p.2.32
Thermostatic Mixing Valves (TMVs)
TMV servicing
“To maintain protection again scald risk, TMVs require regular routine maintenance carried out by competent persons in accordance with manufacturer’s instructions”. – HSG 274 part 2 table 2.1
TMV replacement
“Where a scalding risk is assessed as low (e.g. where health users immerse their whole body), type 2 TMVs that can be overridden by the users are required by building regulations. Where a scalding risk is considered significant (e.g. where users are very young, very elderly, infirm or significantly mentally or physically disabled or those with sensory loss) then type 3 TMVs that are pre-set and fail-safe should be provided (but are required at healthcare premises) and should be checked regularly to ensure they are fail-safe if the cold water supply pressure is interrupted”. – HSG 274 part 2 box 2.3
TMV pipework exceeds 2m
“Where a single TMV serves multiple tap outlets, the risk can be increased”. – HSG 274 part 2 p.2.76 This also applied to TMV’s positioning from the outlet.
TMV install
“Where a risk assessment identifies a significant scalding risk is present, e.g., where there are very young, very elderly, infirm or significantly mentally or physically disabled people or those with sensory loss, fitting TMVs at appropriate outlets, such as hand washbasins and sinks is required.” – HSG 274 part 2 p.2.75
HTM 04-01: Supplement – Performance specification D 08: thermostatic mixing valves (healthcare premises) See HTM 04-41 extract.
Page 6 – “it is recognised that users of domestic hot water for ablutionary purposes in health and social care establishments, particularly vulnerable people (see Note below), can be at risk of injury by scalding”. “’Vulnerable people’ are defined in Health and Safety Executive’s Health Services Information Sheet 6 as:
- children
- older people
- people with reduced mental capacity, mobility, or temperature sensitivity
- people who cannot react appropriately, or quickly enough, to prevent injury”
TMV removal
“Where a risk assessment identifies the risk of scalding is insignificant, TMVs are not required” – HSG 274 part 2 p.2.75
Other Areas
New system chlorination required
“Where necessary, hot and cold water services should be cleaned, flushed and disinfected in the following situations, as specified in the NS 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 pressured tested”. – HSG 274 part 2 p.2127. More examples as to when a disinfection is required.
Weekly flushing
“Flush the outlets until the temperature at the outlet stabilises and is comparable to supply water and purge to drain”. – HSG 274 part 2 table 2.1
Descaling
“Dismantle, clean and disinfect removable parts, heads, inserts and hoses where fitted”. – HSG 274 part 2 table 2.1
Why choose uRisk?
Over 25 years of water hygiene and legionella control experience.
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All staff are trained water hygiene consultants and engineers.
With engineers located all across the UK, we’re never too far away.
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Your one stop shop for Legionella control, no need to go elsewhere.
