How to Turn Off a Stopcock (Which Way to Turn)

Which way do you turn a stopcock to turn it off?

Clockwise closes it. Stand facing the handle, as if you were reading a clock on the end of the spindle, and turn it the way the hands go. Anticlockwise opens it again. Thames Water gives the same direction for both the inside valve and the outside one, and it holds for every ordinary stopcock in a UK home.

How far you turn depends on the kind of handle your stopcock has. Look at it before you start, because the two main types behave very differently.

• Crutch or wheel handle on a brass body (the traditional stopcock): turn clockwise until it stops. That can take several full turns. The water slows gradually rather than cutting off at once.
• Lever handle (a quarter-turn ball valve): turn the lever through 90 degrees. When the lever runs along the pipe the water is on; when it sits across the pipe the water is off.
• Blue plastic tap on a plastic supply pipe: most of these are quarter-turn too. Some have an arrow or ON and OFF moulded on the top.
• A small box on the wall with a switch, usually labelled Surestop: this is a remote stopcock. Flick the switch to off and the valve on the pipe closes itself using the water pressure.

Hand pressure only. If a handle will not move with a firm grip, stop and read our guide to a stopcock that won’t turn before reaching for a wrench. Forcing an old spindle can snap it, and then you have a leak and no way to shut it off.

Turning the water off at the mains: step by step

If water is coming through a ceiling or out of a split pipe, do these in order and do not stop to mop up first.

• Find the stopcock where the supply pipe comes into the house. In most London homes that means under the kitchen sink, below the stairs, behind a panel near the front door, or in a cellar or cupboard under the floor. Where to find your stopcock has the full list of places to look.
• Clear the cupboard and get a torch. Check that the pipe with the valve on it runs down into the floor or through the front wall: that is the incoming main, not a pipe to the washing machine.
• Turn clockwise by hand until the handle stops. Do not keep leaning on it once it is firm.
• Open the cold tap at the kitchen sink. It should run for a few seconds, then slow to a dribble and stop as the pipe empties.
• Flush a toilet once. If the cistern refills and it is fed from the mains rather than a loft tank, water is still getting through the stopcock.
• If electrics are wet or water is near sockets, switch off at the consumer unit before you touch anything else, unless the unit itself is wet or you would be standing in water to reach it.

You turned it off but water is still running

There are three usual reasons.

First, the water in the pipes has to drain out. On a long pipe run or a tall house, taps can trickle for a minute or two after the valve is shut. Give it time before deciding the stopcock has failed.

Second, some of your house may not be fed directly from the mains at all. Many older London houses have a cold water tank in the loft that feeds the bathroom taps, the toilets and a hot water cylinder in an airing cupboard. Shutting the stopcock stops that tank refilling, but everything already stored upstairs keeps flowing. A burst on a tank-fed pipe will carry on until the tank is empty unless you also close the gate valve on the pipe leaving the tank, or open the bath taps and flush the toilets to drain the tank quickly.

Third, the stopcock itself may be worn. Inside a brass stopcock a small washer on a part called the jumper presses down onto a seat. After years of hard water that washer hardens or the seat pits, and the valve turns fully without shutting completely. The kitchen tap keeps running at a thin, steady stream however long you wait. That valve is passing and needs repair or replacing; see stopcock repair and replacement for what the job involves.

If a leak is serious and the inside stopcock will not stop it, the outside stop valve in the pavement is the next step. Thames Water says it should only be used in an emergency. Our guide to the external stopcock explains how to find and use it.

What to switch off at the same time

A stopcock cuts the cold supply. What else needs attention depends on how your hot water is made.

With a combi boiler, hot water comes straight from the mains, so it stops as soon as the cold does. The boiler will simply not fire for hot water. You can leave the heating running; the heating circuit is sealed and separate from the supply you have just turned off. If the leak is on or near the boiler itself, switch the boiler off at its fused spur if the spur is dry, and do not open the casing.

With a hot water cylinder and a loft tank, leave the immersion heater and the boiler on unless you are going to drain the system. If you do drain down, switch the immersion heater off at its switch first. An immersion element in an empty cylinder can burn out.

With an unvented cylinder (a sealed cylinder fed from the mains, often with a small expansion vessel and a pressure valve nearby), switching the stopcock off is fine for an emergency, but anything more than that is a job for someone qualified to work on unvented systems under Building Regulations Part G.

Turning the water back on without an airlock or a burst

Once the repair is done, open the stopcock slowly, a turn at a time, anticlockwise. Opening it in one go sends a pressure wave down pipework that has been standing empty and can blow a weak joint or knock loose the debris inside old pipes.

Leave the kitchen cold tap open while you do it. It will spit air and may run cloudy or brown for a short while; let it run until it clears. Then open each other tap in turn, lowest first.

When the valve is fully open, turn it back a quarter turn clockwise. This leaves the spindle free to move and makes it far less likely to seize in the open position, which is how most stopcocks end up stuck.

If some taps now run weakly or not at all, there is probably air trapped in the pipework. That is common on tank-fed systems and our guide to clearing an airlock takes you through it.

When it cannot wait for the morning

Call an emergency plumber now if water is coming through a ceiling or light fitting, if the stopcock will not turn or will not stop the flow and the leak is getting worse, or if you have shut everything and still have water running where it should not be. Those are the cases where a few hours cost more than the call-out.

An engineer will isolate the supply properly, at the outside valve if necessary, make the leak safe and then deal with the stopcock itself if it is the weak link. The £60 call-out applies at any hour, day or night, anywhere inside the M25, and the repair price is agreed with you on site before any work starts.