Hot and cold water systems - things to consider

Keep the volume of water stored to a minimum (just enough for 1 day's usage).

If using multiple tanks, ensure they are linked together so that water flows through each of them, avoiding stagnation in any one tank.

Record the total consumption of cold water of a typical day.

This check ensures the continuous flow of cold water to help avoid stagnation.

Ensure incoming and stored water remains at a temperature of less than 20°C. For example, store the tank in a cool place and provide insulation.

For more information, you can watch a video on testing a cold water storage tank.

Check the temperature at ball valve outlet every 6 months and record any findings.

The most convenient place to measure is usually at the ball valve outlet to the cold water storage tank. It is useful to consider maximum temperatures recorded by a fixed maximum and minimum thermometer.

Fit the tank with a tight-fitting lid and air vent. Maintain the tank in a clean condition.

Check to ensure the tank remains clean, at least annually.

Visually inspect cold water storage tanks and carry out remedial work where necessary.

Check water temperature at sentinel outlets on a monthly basis.

Check representative outlets for temperature as above on a rotational basis.

After running the sentinel taps for 2 minutes the temperature should be below 20°C. You must record your findings and check annually.

This action helps to ensure 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.

For more information, you can watch a video on testing a sentinel outlet.

Carry out a visual check, when possible, on internal surfaces of cylinders for scale and sludge.

Check to ensure the tank remains clean, at least annually.

It is useful to sample water from hot water cylinders to note the condition.

Check the flow and return temperatures at calorifiers. Outgoing water should be at least 60°C.

Check the water temperature at sentinel outlets on a monthly basis.

Check representative outlets for temperature as above on a rotational basis.

If thermostatic mixer valves (TMVs) are fitted, measure temperature at the hot water inlet to the TMVs.

Monthly checks should be carried out and findings recorded.

The water temperature should be at least 50°C within 1 minute of running the water.

The water supply to the TMV should be at least 50°C within 1 minute of running the water.

Hot water should be stored at 60°C at least 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 the supply and return temperatures on each hot water loop are unchanged (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.

One way of measuring this is to use a surface temperature probe.

For more information about water temperature and testing, you can watch videos on:

• testing outgoing water is at least 60°C
• testing a sentinel outlet
• testing the temperature at the hot water inlet

Avoid long pipe runs between TMV and the outlet.

Pipe runs downstream of TMVs should not exceed 2m.

An assessment should be carried out to determine if residents are immuno-compromised and consequently classified into the ‘at risk’ group.

Sampling for legionella from water system should be carried out.

Samples should be taken from appropriate outlets and storage tanks and cylinders. These should be analysed by an accredited competent company.

Periodically (as identified through risk assessment).

Avoid stagnation, unnecessarily long pipework runs, and transfer of heat from other sources.

Remove dead ends and 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 (hot water pipes).

For infrequently used outlets, instigate a programme of regular flushing (weekly).

Flush through and purge to drain, without release of aerosols.

Avoid build-up of contamination on or in showerheads and associated hoses.

Dismantle, clean and descale showerheads.

This should be carried out quarterly or as determined by risk assessment.