How to Fit an Outside Tap — UK Regs and DIY Method
An outside tap is one of the most valuable UK DIY plumbing jobs — £80 in parts vs £250+ fitted. WRAS requires a double check valve on any external outlet. Here is the compliant method.
Step-by-step method
1. Choose the wall exit point
Drill through the wall from inside to outside, level with the internal pipe you'll tap into. 15mm copper is standard.
2. Fit the isolator + drain
Inside, fit a 15mm tee with an isolator valve AND a drain-off. In winter you'll close the isolator, open the outside tap, open the drain — empties the exposed pipe.
3. Fit the double check valve
Between isolator and outside tap — mandatory under WRAS regs. Screwfix code 91411 (£8).
4. Pipe to outside and fit the tap
Push copper through the wall, seal externally with expanding foam or silicone. Screw the wall-mount tap onto a 1/2" BSP wall plate elbow.
5. Insulate
Fit an insulated tap cover for winter. Or use a self-draining garden tap that empties automatically.
Frequently asked questions
Do I need building regs for an outside tap?+
No — but WRAS requires the double check valve to prevent back-siphonage of contaminated garden water into the mains.
How do I stop an outside tap freezing?+
Close internal isolator, open outside tap and drain-off in November. Refit insulated cover. Reopen in April.