Many old outdoor taps come with a double check valve built into the tap itself. The problem with these is that the check valve could fail in bad weather conditions, so they changed the rules and insisted that all the outside taps should have a separate check valve fitted indoors. However, older taps were allowed to keep their built-in check valve, and if you replace one of these taps you can replace it like for like i.e. with a tap with a built-in valve. However, if you opt to replace such a tap with one that doesn’t have a built-in valve you must fit a double check valve inside the house, as close as possible to the outdoor tap. A Kensington Plumber can do this.

Tools and materials.
New stop tap.
Adjustable spanner.
PTFE tape.

1). Turn off the cold water, the outside tap should have an isolation valve fitted so you ought to be able to turn the water off at that point without affecting the rest of the house. Open the tap to ensure the water is off. If your existing tap doesn’t have an isolation valve, fit one. This valve allows you to turn off the tap in winter and eliminate the risk of flooding due to frost damage. Kensington Plumbers deal with floods.

2). Use an adjustable spanner to undo the old tap. As you do it count the number of full rotations needed to get it out.

3). Take the new tap and wrap PTFE tape around the thread in a clockwise direction use at least four full wraps.

4).Put the new tap on the backplate and tighten it, using the same number of turns as you needed to remove the old one. (PTFE will keep a joint dry even if it isn’t completely tight, but not if you’ve tightened it and then loosened it off, then this is why we’re counting the number of turns).

5) With the tap in the right position, close it and turn the water back on. Check the back of the tap for leaks. If you think there’s a leak repeat the steps but use more tape this time, or maybe even a smear of jointing compound over the thread, remembering that you should use compound suitable for drinking water.
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