The mains water stop valve may need replacing if it has completely seized or you may need to move the stopcock as it is commonly called to a more suitable position.
Turning Off the Water
Before carrying out repairs, replacing or moving the mains stop valve in your house you will need to isolate the water supply. This can be done by switching off at the Water Authority’s stop valve out in the street. These can sometimes be difficult to find but are normally in the pavement just outside the boundary of your property. The cover to these is usually marked. If you cannot find it you may need to ask the Water Authority for your area or, have a chat with the neighbours. Note that these valves may also control water to some of your neighbours so you’ll need to let them know before closing it. Depending on the valve, you may need a special key to switch this off
Replacing the Stopcock
Before starting, make a note of the flow direction – this will be marked on the body of the valve. Also make sure your new valve is the same size and that no pipe alterations will be needed. With the water switched off at the Water Authority stop valve in the street and the pipe work drained, you can remove the stop valve by holding the valve body with a wrench, and undoing each of the compression nuts. Slide the nuts back away from the valve and, with a little coaxing, the valve can be removed. Remove the olives from the ends of the pipe on either side. These can be helped with a gentle twisting using a pipe wrench. If they’re stuck fast, cut through them carefully with a small hacksaw. Cut at an angle and make sure you don’t damage the pipe at all. With these out of the way, take the old compression nuts off as well
Put the new compression nuts over the pipe ends and slide them along out of the way. Put a new olive on each pipe end and position the valve. You can use a little PTFE tape around the olives to ensure a good seal – not on the compression thread which is a fairly common mistake.
Tighten the compression fittings holding the body of the valve with a wrench as you do it. These nuts should be tight but not overdone. You can always nip them up a bit but if they’re over tightened, you’re back to the beginning. Close the valve by turning clockwise. Close the kitchen tap, the drain valve and any other open outlets. Switch the water back on and open the valve gradually so that you can inspect for leaks. If all is well, open the kitchen tap and allow to flow for a minute so that any air is released and the pipes fill up.
Moving a Stopcock
It’s perfectly possible to move the mains stop valve on the water supply coming into your house but it’ll need a bit of planning. If you’ve ever fitted a new kitchen or built an extension you’ll know how the stopcock always seems to be in the most inconvenient place for your plans.
Lead Pipe
If the mains up to the stop valve is made from lead you will need to use a special fitting to connect the old lead pipe to a short tail of copper before fitting the new stop valve. Carefully measure the size of the lead pipe and take these details with you to the plumbers merchant so that you can get the correct adaptor. Lead is toxic and relatively easily damaged so take care with it.
Planning the New Stop Valve Position
Before starting work, make sure you have carefully planned where the new stop valve will be located so that it is easily accessible and as near to the point where the mains water enters the house as possible. There also needs to be a drain valve immediately after the stop valve allowing for the internal plumbing to be drained down. All in one stop valves with integrated drain valves are available and make for a quicker job. With the water switched off and the pipe work drained, you can remove the old stop valve by holding the valve body with a wrench, and undoing each of the compression nuts.
Adapting the Pipe Work
More recent installations will have blue plastic pipe supplying the mains water. Cut this back to the required position and using a push fit plastic to copper adaptor, extend with a short copper tail ready to fit the new stop valve. Don’t use a hacksaw or similar to cut the plastic pipe as this will not give a clean cut. The burred end will not make for a good connection. Special plastic pipe cutters have a blade and jaw arrangement allowing the pipe to be cut neatly and cleanly. Make sure the cut is square. Fit the insert into the plastic pipe end and push the connector fitting onto the pipe so that it fully engages and locks. Cut the short length of copper pipe required and insert into the other side of the adaptor again ensuring it engages fully.
Fitting the Stop Valve
Run the internal water pipe back to the position of the new valve so that the gap between the two pipes is suitable for the space required for the new stop valve.
Before starting, make a note of the flow direction – this will be marked on the body of the valve. Put the new compression nuts over the pipe ends and slide them along out of the way. Fit an olive on each pipe end and position the valve. Tighten the compression fittings holding the body of the valve with a wrench as you do it. These nuts should be tight but not overdone. You can always nip them up a bit but if they’re over tightened, otherwise you’re back to the beginning. Close the valve by turning clockwise. Close the kitchen tap, the drain valve and any other open outlets. Switch the water back on and open the valve gradually so that you can inspect for leaks. If all is well, open the kitchen tap and allow to flow for a minute so that any air is released and the pipes fill up.