In 2013 the HSE removed an artificial 300 litre limit meaning that smaller domestic hot and cold-water systems now come under the scope of the Health and Safety Executives (HSE) Approved Code of Practice (ACOP L8) L8 and technical guidance HSG 274.  The guidance deals with water used for a domestic purpose which is defined as cooking, washing and cleaning.

As domestic water systems generally present a lower risk from Legionella bacteria they do not require the same level of assessment, control and prevention measures as larger types of buildings and systems.  For example, measures such as regular monthly temperature monitoring are seen as impratical for most domestic sites.

The HSE accepts that as domestic systems present a lower risk, measures such as temperature monitoring can be carried during regular inspection and service visits.  Where the property is used for short term lettings such as an Air BnB then it is expected that the property will be inspected more often than properties used for longer term lettings.

For longer term lettings it is generally expected that the tenant will be responsible for cleaning their own shower heads.  In a short term holiday type lettings the cleaning and disinfection of showers would be organised or carried out by the Duty Holder.

By answering the following questions you can produce a Legionella Risk Assessment suitable for a low risk domestic property.

If any deadlegs are found during the assessment they should be immediately removed by cutting the pipework back to where there is regular movement.

The final risk assessment will include control and prevention measures appropriate for a domestic property and gives advice on the water temperatures required to minimise the risk from Legionella bacteria.

Please Note, the risk assessment template is not suitable for increased risk fixtures, fittings or systems such as hot tubs, steam rooms or swimming pools.

Once complete and submitted you can immediately download a copy of the assessment but if not, don't worry because a copy will also be emailed to you.  The assessment should be kept along with other water related records such as boiler servicing and temperature monitoring records.  These records form what is regularly called a "Logbook".

It is recommended that once complete a copy of the risk assessment is given to the tenant, resident, guest or is included in any welcome pack so that you can demonate you have considered/addressed the risk of Legionella bacteria at the site.

Not all tanks with water in them are Cold Water Storage Tanks, some tanks supply outlets, some supply water heaters and some supply heating only systems.  Tanks need to identified correctly as the purpose of tank changes the required measures.  The picture below shows how tanks may be set up.

Cold water storage tanks should be installed in compliance with the Water Supply Regulations and Scottish Water Byelaws. The storage temperature of a cold-water storage tank should not exceed 20c. Where the tank supplies outlets as well as a water heater the temperature should not exceed 25c although this is not ideal. Where the tank is used as a Header Tank or Feed and Expansion Tank the storage temperature is increased to a maximum of 38c.

How a Cold Water Storage Tank should be installed.

Combi Boilers, Electric Showers and Instantaneous Water Heaters of all types should ideally be able to achieve an outlet temperature of at least 50c.

Water heaters that store hot water over 15 litres in capacity (vented and unvented water heaters) should do so at a temperature of not less than 60c, this is a legal requirement of the Water Supply Regulations, Part G3 of the Building Regulations as well as a requirement of the Health and Safety Executives Approved Code of Practice L8.  Hot water should be distributed at a temperature of at least 50.c and when a circulation pump is used the return hot water temperature should be at least 50c.

Expansion vessels have the potential to be a breeding ground for bacteria. Water may remain in an expansion vessel for a period of time and at temperatures that could promote bacterial growth especially where the water heater is infrequently used. Expansion vessels should be fitted upright with short pipe runs to minimise the risk of water being retained in the vessel.

Types of Expansion Vessels

Hot water should be distributed so it reaches outlets (or TMV inlet) at a temperature of not less than 50°C within one minute of fully opening the outlet. Longer time scales and lower temperatures are allowed for low risk instantenaoues hot water systems. For most people, the risk of scalding at this temperature is low. Where there is a risk of scalding Thermostatic Mixing Valves (TMV) should be considered and be fitted in line with current guidance

Cold water should reach outlets at a temperature less than 20c within two minutes of fully opening the outlet.

Thermostatic Mixing Valves (TMV) are valves that use a temperature sensitive element and blend hot and cold water to produce water at a temperature that safeguards against the risk of scalding, typically between 38°C and 46°C depending on outlet use. The blended water downstream of TMVs may provide an environment in which legionella can multiply.

Part G3 of the Building Regulations requires TMV valves are fitted to baths and the Water Regulations require a mixing device is fitted to a shower.

TMV valves require regular monitoring by taking and recording the hot water temperature into the valve. This is to prove the temperature up to and into the valve meets the various temperature and performance requirements and that the valve is in working order.  In the example below the temperature into the valve is 58c. The mixed temperature out of the valve is 41.c. This check needs to be carried out at the "Temperature Monitoring" frequency recommend in the risk assessment.

Where to take water temperatures on a Thermostatic Mixing Valve (TMV).