Mains water flushing

To deliver high-quality drinking water to you, 24/7, we have to keep our systems in tip-top condition. To achieve this we carry out a variety of maintenance jobs.

One of these is to periodically flush some of our water mains, particularly if we believe natural iron sediments have built up inside them.

To find out if we’re planning to flush the mains in your street, check out our maintenance and improvements section In Your Area.

What do we do?

We open hydrants on the water mains, across the area we are working in, to flush the water out at high speed. This process stirs up and removes any sediment in the water mains.

A couple of weeks before we’re due to start work you’ll receive a letter with dates and information about the programme in your area.

You may only be directly affected for a few hours as we flush past your property, although we may need to do this on more than one day when working in an area.

Why are we doing this?

Many of our water mains are made of iron and this means that, over time, iron sediments build up in them. If left alone these sediments are harmless and do not cause any problems, however if they’re disturbed, when fire fighting or due to a burst main, they can be displaced, causing the water to discolour. Although discoloured water is harmless, we appreciate this may look unsightly, so want to reduce the risk of this happening. Flushing is an effective way of keeping some older mains in use – helping to keep your bills low.

Do I need to do anything?

To minimise any inconvenience, during the dates on your letter, we recommend the following:

fill your kettle, or a suitable container with drinking water before work starts
don’t use washing machines, dishwashers etc. or leave taps open
don’t use mains fed instantaneous water heaters/showers if the water supply is interrupted (central heating will be fine)
if you have a water softener, isolate it using the bypass pipe work until the flushing is completed
don’t fill or change the water in fishponds or tanks for 48 hours.

If you have lost your letter, you can visit In Your Area in the maintenance and improvements section to find out when we are working in your neighbourhood.

What happens to the water used?

As a rule of thumb – we use twice the volume of any pipe when we flush it.

Because of the large amounts of water used to flush clean a water main, we usually allow the water to soak through verges (boosting ground water levels) or we allow it to run into drains and sewers before flowing back into rivers through our network of Water Recycling Centres.

While flushing is a critical part of maintaining high-quality drinking water, we’re committed to water conservation and work hard to make our programmes as efficient as possible.

How will I be affected?

If we’re planning any flushing in your area, we’ll write to you beforehand. Your water will continue to be safe to drink but on the dates between the start and end of the flushing you may:

notice your water is discoloured or cloudy
experience low pressure
be interrupted for short periods of time.

If you’re a business customer, contact your provider for more information.

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Mains water flushing