Legionella sampling can be used as a great reassurance measure or alternatively to show in an empirical way failings in a buildings or systems control measures.
HSG 274 Para. 2.121
Where monitoring for Legionella is considered appropriate in hot and cold water systems, sampling should be carried out in accordance with BS 7592 Sampling for Legionella organisms in water and related materials.
HSG 274 Para. 2.122
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 (ie 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, crossflow from the water system or other anomaly
Overview
Depending on the water system(s) installed, Legionella sampling may or may not be a requirement. Cooling towers, spa pools and some process systems need routine sampling in order to prove control.
In domestic water systems there are circumstances where sampling is recommended under HSG274 Part 2 (HSE’s published guidance), these include:
- Initially on systems when biocides are used and temperature is reduced (monthly for approx. 12 months)
- Where the efficacy of the control regime is in doubt – eg. failures in temperature or biocide regime (weekly sampling advised)
- High risk areas eg. hospital wards with particularly at risk patients, care homes etc.
- Suspected or confirmed Legionellosis associated with water system
- If the risk assessment says so
In addition sampling as part of a risk assessment can be a good tool for reassurance particularly in water system(s) where the present risk and control is not known.
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Legislative Cascade
The Health and Safety at Work etc. Act 1974
The Management of Health and Safety at Work Regulations 1999 (MHSWR)
The Control of Substance Hazardous to Health Regulations 2002
The Notification of Cooling Towers and Evaporative Condensors Regulations 1992
ACoP and Guidance L8 2013
HSG 274 Technical Guidance
BS 8580-1:2019
HTM 04-01
HTM 01-05
HSG 220 Care Homes
HSG 282 Spa Pools
