The rule that matters: backflow protection
Water regulations require outside taps to be protected against backflow — dirty water being sucked back into the drinking supply, for example from a hose in a pond. Most kits include a double check valve, or the tap has one built in. Never fit an outside tap without one.
Plan the route
- Find a cold mains pipe close to the outside wall — often under the kitchen sink.
- Check there are no cables or pipes where you will drill.
- Place the tap at a handy height above the ground, away from doors.
Step by step
- Turn off the stopcock and drain the cold.
- Cut in a tee on the cold mains pipe.
- Fit an isolation valve (with drain-off if possible) and the double check valve.
- Drill through the wall, sloping slightly down to the outside, and sleeve the hole.
- Run the pipe through and connect to the wall plate elbow.
- Screw the tap into the wall plate with PTFE on the tapered thread, facing down.
- Seal around the pipe outside with silicone.
- Turn on and test all joints inside and out.
Pro tip: The tap thread into the wall plate is a tapered thread that seals on the thread — that is where PTFE goes. The compression joints inside seal with olives — no tape on their threads.
Winter care
Before frosts, turn off the inside isolation valve, open the outside tap to drain it, and leave it open. Fit an insulated cover. This prevents burst pipes.
