Why do water mains burst more during winter months?

During winter months we see a lot more burst mains and leaks on our network. In the last five years we have spent £220 million renovating and replacing mains to reduce interruptions to supply. But we can’t replace the whole network at once, so it is likely that during the colder months we will see more burst mains.

Why does this happen?
At peak times, such as early mornings, when more people are using their taps or showers in the their homes the pressure inside a water main drops, when they stop using the water the pressure increases, this can cause slight movements in the water main. During the winter and really cold weather the ground temperature drops causing the ground to freeze and contract, this contraction combined with the pressure in the water main can lead to movement of ground around the main causing stress fractures, or small cracks, to occur allowing the water to escape. We also see an increase of bursts and leaks when there are large temperature changes.  During this thawing period, the ground temperature warms up swelling the ground; this can also cause additional stresses on the main, especially if the thawing period is rapid. Again causing damage which may lead to a burst or fracture. Many older pipes are made from cast iron which is more brittle and ridged than the more modern ductile iron or plastic water mains. Therefore, we tend to see more bursts or leaks on older mains. Our programme of works will eventually see all mains replaced or renovated to more modern materials which will see a reduction in bursts, but generally it is out of our control to stop all burst mains during cold weather. Did you know, that 25% of all leaks are on the customer’s side of the pipe? You can take some easy steps to prepare your home for winter. Click here to find out more.