What to do when mains water gets warm

mains water

During the recent hot weather we have noticed an increase in the temperature of mains water, to as much as 23°C or 24°C. While there is nothing which can be done about this until it naturally cools as the heatwave subsides, it does present a further challenge for Legionella control and makes monitoring and management of the risk even more important. Given that Legionella occurs naturally in a wide variety of water sources, and proliferates at temperatures between 20°C and 50°C, remaining vigilant about the storage and movement of water in a manmade plumbing system will help to mitigate the inherent risk presented by warm mains water.

Know your temperatures

Information is power, as they say, so make sure that you are on top of temperature checking of the incoming mains water. Take regular readings (daily, if there are concerns about water warmth) and record the results. Start with the sentinel tap furthest from the cold water storage tank. Let it run for two minutes, with your thermometer in the flowing water. Work your way through other cold water outlets on the premises and make a note of all your findings. You should also check the temperature of the water in the cold water storage tank, particularly as stored water is at higher risk if it isn’t kept moving regularly.

You can find more information about temperature monitoring here.

Flushing matters

The requirement to keep water flowing through the plumbing system is also vitally important for reducing Legionella risk. Stagnant or non-moving water can be a breeding ground for bacteria, whether in tanks or pipework (particularly in long runs of pipe, dead legs and blind ends), so weekly flushing of little-used outlets is very important.

Again, keeping a record of your flushing regime (which outlets have been flushed, by whom, for how long and when) is also recommended, to ensure that there is a paper trail to demonstrate your compliance.

Flushing needs to be kept up once started, as studies show that starting and then stopping actually increases the risk of Legionella growth. There is also a recommended method for flushing water outlets, as follows:

For a shower, first turn it onto its hottest setting and ideally remove the showerhead. If this isn’t possible, cover it with a towel or plastic bag to minimise the creation of airborne water droplets. If the showerhead has different flow settings, you should run the water through each setting for several minutes at a time.  If the shower has a flexible hose, move it around vigorously during flushing to remove any biofilm or bacteria which may be in the tubing.

When flushing taps, run each one for at least five minutes. Turn the water on slowly so you don’t splash it, to avoid releasing potentially contaminated water droplets into the air.

More guidance on flushing can be found here.

Keep it clean

Cleanliness of the plumbing system is another important factor in controlling Legionella risk, and never more so than when incoming mains water is on the warm side. Sludge, limescale, sediment and debris in the tanks or pipework can all provide a source of food for bacteria, so now is a very good time to give your system a thorough inspection and clean any areas of concern.

If you find evidence of unwanted dirt, in many cases a good scrub will do the job. In others, rusty components or otherwise old or decrepit system parts may need replacing. Sometimes a chemical flush will be required to eliminate contaminants.

Don’t be afraid to seek professional advice or commission a specialist firm to carry out remedial work if necessary (details of our services can be found here).

Seek help if required

When mains water is in the temperature ‘danger zone’ there is no need to panic, but there is a requirement to ensure that proper water hygiene management practices are in place. If you need advice or practical help with reducing the risk of Legionella, please get in touch.

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