How do I drain an outside tap for winter?

Water expands as it freezes, and copper does not stretch. A frozen outside tap supply usually splits inside the wall or in the pipe run behind it, and the leak only shows when it thaws — often into a kitchen unit or a cavity.

What you'll need

• Access to the internal isolating valve
• Pipe lagging for exposed sections
• A tap cover if the tap is very exposed

Step by step

1. Find the isolating valve.It should be on the internal pipe feeding the tap, usually within reach of where the pipe passes through the wall. If there is none, that is the first thing to put right.
2. Do it before the first frost.Late October or early November in most of the UK. A single unexpected cold night is all it takes.
3. Disconnect any hose.A hose left connected holds water against the tap and prevents it draining. It will also split itself.
4. Close the isolating valve.Quarter turn so the slot is across the pipe. Confirm by opening the tap — the flow should stop after the residual water has run out.
5. Leave the tap open all winter.This is the step people skip. An open tap lets the exposed section drain fully and gives any remaining water room to expand rather than splitting the pipe.
6. Open a drain-off if there is one.Some installations have a small drain point between the valve and the wall. Open it into a container to clear the last of the water.
7. Lag the pipe in unheated spaces.Any run in a garage, an outbuilding or an unheated utility area needs foam lagging. So does the section inside the wall if it is accessible.
8. Fit an insulated tap cover if it is very exposed.A moulded cover over the tap head adds useful protection on a north-facing or wind-exposed wall, though it is no substitute for draining.
9. Reverse it in spring.Close the tap, then open the isolating valve slowly, and check for leaks. A tap that has been frozen may only reveal its split when the pressure returns.
10. Check for damage in spring.Look and listen at the internal pipework as the water comes back on, and check inside the cupboard and the wall for damp.

Tips

• Leaving the tap open is what does the work. Closing the valve alone leaves a sealed section of water in the wall.
• Put it in the autumn checklist alongside gutters and heating. It takes five minutes and prevents a genuinely expensive repair.
• If there is no isolating valve, fitting one is a small job and it makes this possible every year afterwards.

Common mistakes

• Closing the isolating valve but leaving the tap shut — The water between the valve and the tap is trapped in a closed section. When it freezes it has nowhere to expand and it splits the pipe or the tap body.
• Leaving a hose connected over winter — It holds water in the tap and in the hose, and the hose itself will split. Disconnect and drain hoses, and store them somewhere frost free.

If it doesn't work

Questions people ask