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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, i.e. 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, e.g. if necessary site storage tank in a cool place and provide insulation.

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 e.g. 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

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.

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, i.e. 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, i.e. hot water pipes

How often?

For infrequently used outlets, instigate a programme of regular flushing, i.e. 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

Updated 2014-08-12