How do you fix a burst main?

We know how important water is to your daily life. It’s not just for drinking; it’s for cooking, cleaning, washing, flushing the toilet, and having water supplied to your home simply makes life better. Water supply interruptions only affect a small number of our customers every year but we know it is really frustrating if it happens to you, so we invest millions to try and stop this from happening. That being said, burst water mains do happen from time to time and so here we try to explain what goes into fixing a water main, repairing the leak and getting your water back on to your tap. At this point it is important to note that every burst water main or water leak is different and therefore the exact fix will change and the time taken to repair the water main will vary. This just gives you an idea of the general things and obstacles we face every time there’s a burst or water leak.

Types of water mains

Before we get started it is good to know that we have three different types of water main.

Trunk Mains – These are the large diameter water mains that move water around the region. So for example these mains would bring water from Purton in South Gloucestershire to the Bristol Region. The water is then, generally, stored in service reservoirs.

Distribution Mains – These are smaller in size than trunk mains and move water around local areas. So you may see (well they’re buried but you know what I mean) these types of main around housing estates or residential areas.

Communication/ Supply pipes – These are the pipes that supply the water to the individual properties. They can come off either trunk mains or distribution mains.

The amount of people affected by a burst water main or leak, and often the length of time to fix, is determined by the type and size of the water main the burst or leak is on.

How do we know there is a burst water main?

We’ve been supplying water for over 170 years and so parts of our network are old. Not quite 170 years old but some mains have been in the ground for upwards of 60 to 80 years. So they aren't all covered in sensors letting us know what’s going on. Often we know a burst water main has happened due to changes to the water flow or pressure in other parts of our network which is picked up by our 24/7 control room. But we also rely on our customers reporting having no water or spotting water leaks. Our customers really are the eyes on the ground so can give us a lot of information.

What happens once a burst water main has been reported?

First thing we do is send one of our Operations team out to investigate. Our first thought is always “how do we get the water back on for people”. Sometimes this can be done by “rezoning” which is essentially bringing the water to your area via a different set of water pipes. This can be done by turning some valves in the area which changes the route. By doing this most, if not all, people affected by the burst main will see their water supply return. If it is possible we, more often than not, see the water back on within an hour. It means that you don’t have to wait for the water main to be fixed to get your water back. Happy days. If a “rezone” isn’t possible, we will then need to fix the water main before your water supply returns. The length of time taken to repair the water main can vary, and there are so many factors that play apart, but most are fixed within three hours.

Detecting the burst

Might sound simple as often you have water showing, but not always. Sometimes we don’t see any water above ground and often water does show but up to 500 meters down the road. And although there are some fancy things you can do with satellites to detect bursts or leaks the most effective and quickest way is to listen to the water main. Listening to the sound the water main is making and knowing what it is telling you is a real skill. There is a wealth of experience and knowledge in our teams which make it possible to detect water leaks and bursts with some simple equipment. Once we have detected the water leak we need get all the relevant highway notices in place to carry out the work and then make the site safe for our staff and the public so we are ready to dig down on to the water main. And digging down onto the main isn’t always as simple as you might think. Our water mains are in common areas for other utilities as well. So we often find sewers, gas mains, broadband, cable TV, street lighting or electrical cables on top of our water main, and so we need to hand dig safely around them as to not cause more disruption. And if you have water running out of the main too it is not that easy to dig.

Fixing the water main

Once we have exposed the water main and we can see the leak we more often than not need to pump water away safely from the area to be able to access it. Sometimes are team can fix the water main live but you can imagine standing in waist high water in a hole in the middle of winter is not all that much fun. At this point it is important to know the main causes of a burst water main. The two main reasons we see burst a water main is because of deterioration or movement. As said before some of the water mains have been in the ground upwards of 60, 80 years, over that time they wear and therefore occasionally break. We do have a programme to replace all of our network but we can’t do it all at once. Ground or weather conditions can cause movement in the ground surrounding the water main which causes the water main to move. This movement can be sudden or the continued movement over time can cause the water main to bend and eventually break. During cold period or dry periods we often see a lot more movement in the ground so we see higher numbers of burst water mains. There are other reasons for burst water mains including failures at the pipe joints, traffic load at certain areas can cause pressure on the main, and even tree roots can cause issues. Damage to the water main can either be around the circumference of the water main (so around the edge) or they can be along the main. If it’s round the water main then we generally fix it by putting a repair collar around the affected area. This is like a big clamp which fits right round the water main. If the damage is along the water main then we have to cut the piece of affected water main out and fit a new piece of pipe. Fixing the main can be a relatively quick part of the process.

What happens after it is fixed?

The first thing to do is to re-pressurise the main, known as “recharging”. This needs to be done very slowly as to not cause further damage to the main. Depending on the size of the water main it can takes an hour or two to fully recharge, during this time customers may see their water supply return at a lower pressure or flow. During all this sediment is often disturbed within the main and this can cause the water to be slightly discoloured, often an orange or brown, once the supply returns. You can solve this by running the taps for a couple of minutes to clear. Once we have completed the fix we need to start the backfill of the ground and reinstatement of the land, this process may take place over several days dependent on the type of surface we need to re instate. Where the main has been in a road or in a footway we need to return the surface to the high specification as set by the government. And after that we clear up and leave it as if nothing ever happened and we move on to the next.