plumbing

How to Install an Outdoor Tap: Plumbing, Regulations and DIY Tips

Gabriel

03 Nov 2025 — 3 min read

An outside tap is one of the most useful additions to any home — and one of the more straightforward plumbing jobs that a competent DIYer can tackle. The pipework is simple, the connection point is usually accessible, and the whole job can be completed in an afternoon. There are a few regulatory requirements to be aware of, but they're easy to comply with.

Notifying Your Water Company

In England and Wales, installing an outside tap constitutes a plumbing alteration that must technically be notified to your water company (under the Water Supply (Water Fittings) Regulations 1999). In practice, many homeowners don't notify and there are rarely consequences — but the notification is free (a simple form) and failure to comply can technically result in a fine. More importantly, the regulations require you to install a double check valve to prevent backflow contamination of the mains supply — this is a genuine safety requirement.

Required Fittings and Materials

Outside tap kit (includes tap, wall plate, backplate elbow): around £15–30 from Screwfix or B&Q. Alternatively, buy components separately for better quality.
Double check valve (essential for Water Regs compliance): around £8–15
15mm copper pipe (enough to run from your connection point to the outside wall)
15mm isolation valve (allows you to shut off the garden tap separately)
Push-fit or compression fittings as required
PTFE tape
Silicone sealant
Core drill (for boring through the wall) — hire or borrow

Choosing Your Connection Point

Connect to the cold mains supply, not the hot water pipe or a central heating pipe. The ideal connection point is the cold mains pipe under the kitchen sink — it's usually 15mm copper, accessible, and a short run to the outside wall.

If the kitchen is on the other side of the house from your garden, consider connecting to a pipe in the garage, utility room or wherever the nearest cold mains supply runs close to an external wall. The shorter the pipe run, the fewer fittings and the less heat loss in winter.

Step-by-Step Installation

Turn off the mains water supply at the stopcock (usually under the kitchen sink or near the water meter) and drain the pipe by opening a cold tap elsewhere in the house.
Mark your connection point on the pipe and use a pipe slice (around £8 at Screwfix) to make a clean cut. Insert a push-fit tee fitting or use a compression tee — push-fit is faster but compression is more reliable in accessible locations.
Run pipe from the tee fitting toward the wall. Clip every 1–1.2m with pipe clips. If the pipe runs through any unheated areas (garage, loft space), lag it with foam pipe lagging to prevent freezing.
Fit the isolation valve in the run — this lets you shut off the garden tap in winter without affecting the rest of the house.
Fit the double check valve downstream of the isolation valve, observing the flow direction marked on the body.
Drill through the external wall with a core drill (22mm or 25mm hole for a 15mm pipe with lagging). Angle the hole very slightly downward toward the outside so any water ingress drains outward.
Fit the wall plate elbow on the outside, securing to the wall with frame fixings. Run pipe through the hole and connect to the elbow.
Fit the tap itself to the wall plate. Wrap the thread of the tap tail with PTFE tape (3–4 turns clockwise) before screwing in.
Seal around the hole with exterior silicone or mortar to prevent water and draughts entering.
Turn the mains back on, check all joints for leaks, and test the tap.

Frost Protection

An outside tap left connected over winter will freeze in severe cold, potentially splitting the pipe. Two approaches:

Close the isolation valve inside and open the outside tap slightly to drain the pipe — the easiest method.
Fit a self-draining outside tap (the tap drains automatically when closed) — more expensive but more reliable if you tend to forget to winterise.

Foam lagging on the internal pipe run is not optional in unheated spaces — a burst pipe in a garage or loft is a serious and expensive problem.

What You Can't DIY

This work is considered notifiable plumbing under the Water Regulations. An approved plumber can sign off on their own work; a DIYer should notify the water company before starting. If you're uncertain, the Water Regulations Advisory Scheme (WRAS) publishes a helpline and online guidance.