Hot and cold water - Things to consider
Cold water storage and outlets
Storage tanks
What do I need to consider doing?
Keep volume of water stored to a minimum, ie just enough for one day's usage.
If using multiple tanks, ensure they are linked together so that water flows through each, avoiding stagnation in any one tank.
How often?
Record total consumption of cold water of a typical day.
Notes
This check ensures the continuous flow of cold water to help avoid stagnation.
Water temperature
What do I need to consider doing?
Ensure incoming and stored water remains at a temperature of less than 20 °C, eg if necessary site storage tank in a cool place and provide insulation.
Testing a cold water storage tank
How often?
Check temperature at ball valve outlet every six months and record any findings.
Notes
The most convenient place to measure is usually at the ball valve outlet to the cold water storage tank. Useful to consider maximum temperatures recorded by fixed max/min thermometer.
Avoid external contamination, build up of sludge, scale and rust
What do I need to consider doing?
Fit tank with tight fitting lid and air vent. Maintain tank in a clean condition.
How often?
Check to ensure tank remains clean, at least annually .
Notes
Visually inspect cold water storage tanks and carry out remedial work where necessary.
Water temperature - cold water outlets eg taps, showerheads
What do I need to consider doing?
Check water temperature at sentinel outlets on monthly basis.
Check representative outlets for temperature as above on a rotational basis.
How often?
After running for two minutes at sentinel taps, the temperature should be below 20 °C. Record findings.
Check annually.
Notes
This action helps to ensure that the supply and flow of cold water remains at a temperature that will not encourage the growth of legionella.
Selection of representative outlets should be assessment-driven to ensure the entire system is covered over a period of time.
Hot water systems
Hot water cylinder/calorifier
What do I need to consider doing?
A visual check, where possible on internal surfaces of cylinders for scale and sludge
How often?
Check to ensure tank remains clean, at least annually.
Notes
Useful to sample water from hot water cylinders to note condition
Water temperature
What do I need to consider doing?
Check flow and return temperatures at calorifiers. Outgoing water should be at least 60 °C
Testing outgoing water is at least 60°C
Check water temperature at sentinel outlets on a monthly basis.
Check representative outlets for temperature as above on a rotational basis.
If thermostatic mixer valves (TMV's) are fitted, measure temperature at the hot water inlet to the TMVs.
Testing the temperature at the hot water inlet
How often?
Monthly checks should be carried out and findings recorded
The water temperature should be at least 50 °C within one minute of running the water
The water supply to the TMV should be at least 50 °C within one minute of running the water
Notes
Hot water should be stored at 60 °C at least in order to kill legionella bacteria. The thermometer pocket at the top of the cylinder and on the return leg, if fitted, is a useful point for accurate temperature measurement. If installed, these measurements could be carried out by a building management system .
This check makes sure that the supply and return temperatures on each hot water loop are unchanged, ie the loop is functioning as required.
Selection of representative outlets should be assessment-driven to ensure the entire system is covered over a period of time.
Selection of representative outlets should be assessment-driven to ensure entire system is covered over a period of time.
One way of measuring this is to use a surface temperature probe.
Hot water pipework
What do I need to consider?
Avoid long pipe runs between TMV and outlet.
Notes
Pipe runs downstream of TMVs should not exceed 2 m.
'At risk' population
What do I need to consider?
Assessment should be carried out to determine if residents are immuno-compromised and consequently classified into the "at risk" group.
What do I need to do?
Sampling for legionella from water system should be carried out.
Samples should be taken from appropriate outlets and storage tanks/cylinders. These should be analysed by an accredited competent company.
How often?
Periodically (as identified through risk assessment).
For all hot and cold water systems
Pipework
What do I need to consider?
Avoid stagnation, unnecessarily long pipework runs, and transfer of heat from other sources.
What do I need to do?
Remove dead ends/blind ends from the system and ensure regular flushing of dead legs
Keep pipe runs as short as possible
Insulate water pipes in work areas where heat may be transferred from other sources, ie hot water pipes
How often?
For infrequently used outlets, instigate a programme of regular flushing, ie weekly
Notes
Flush through and purge to drain, without release of aerosols.
Showerheads
What do I need to consider?
Avoid build up contamination on or in showerheads and associated hoses.
What do I need to do?
Dismantle, clean and descale showerheads
How often?
Should be carried out quarterly or as determined by risk assessment