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Water main renovation

Bristol Water has an extensive, ongoing water mains renovation programme to renew or line water mains to cut water losses, improve water quality and pressure and improve security of supplies for customers. Over the current 5 year regulatory investment period 2010-2015 we will be investing £50m in renovating over 250 km of mains.

Why pipes need renovating

Bristol Water has over 6,600 km of water mains. Most of these are made out of cast iron and are in some cases more than a hundred years old. Our pipes are laid in a wide range of soil conditions, some of which are very aggressive to pipe materials and are often subject to ground movement from extreme weather conditions and heavy traffic. Inevitably, over time, mains will structurally deteriorate to the point where they need to be renovated. We monitor our network carefully, constantly collecting data that allows us to analyse key aspects of its performance, like burst rates, water pressure and water quality. This helps indicate when particular sections are getting towards the end of their useful life. Further onsite testing is then done to determine the mains exact state from which we can make a decision on whether it needs to be planned in for renovation.

How we renovate

We use a range of techniques to renovate pipes.

Sliplining

Here, a new plastic pipe is inserted into an existing main using the old main as a sleeve. This method has the advantage that we do not need to dig up the length of the road to bury a new pipe. A hole is dug either end of the length of pipe we are sliplining and a new pipe is inserted in one end and pulled through to the other.

Pipe bursting

This method involves breaking the existing main with an impact mole machine, which allows the insertion of a new sleeved plastic main along the same route. The new main can be of the same or of slightly larger diameter to the original. This method is only suitable where the existing pipe is made of cast iron.

Open cut

Where the above techniques are not suitable, we will excavate a new trench within which we lay the new main. This method allows us to put a main of much bigger capacity than previously and choose a new line or level. The old pipe is usually disconnected and left in the ground.

Impact on customer

It is unavoidable that there will be some impact on residents and traffic in the area we are working. Prior to a job starting we will write to residents and give details of the overall plan. This letter will also explain about the possibility that during the work the water supply to some residents might be interrupted for short periods - typically early in the morning and again later in the day. For some customers there will be a need to shut off their water supply for longer periods of up to 12 hours. For these longer outages we will give advance warning about what day they will be affected. This will normally be between 8am and 8pm, although we are usually able to complete the work in a period less than this.

In order for our work to be completed with the minimum of inconvenience, where necessary, ‘no waiting’ cones might be placed on the line of our proposed works. To help ensure our work is not delayed we ask residents not to park in these areas. Occasionally we may also need to close a road to through traffic although access to properties will still be maintained. Advance notice of any road closures will be provided.

Service connections

Very often with these schemes we also replace our length of any metallic communication pipes as these are found to be more prone to corrosion and subsequent leakage. The communication pipe is the length of pipe extending from the connection to our water main to a point where the pipe passes beyond the boundary of the street where it is laid. In most cases a customer’s property.

The replacement pipes will use will be a 25mm polyethylene (plastic) pipes, and should not only improve the water quality, but may also improve flow and solve some poor pressure problems.

At the same time we replace our section we also encourage customers to replace their supply pipe (if it is lead or galvanised iron.) which runs from boundary of the street to their internal water fittings. Information on this is given to customers with their initial letter.