How to replace an outside tap

Video by Plumberparts. This walk-through is based on the video "HOW TO CHANGE A FAULTY OUTSIDE TAP - Plumbing Tips" from Plumberparts, who covers the basic procedure clearly and talks through what to do when the tap body is seized or won’t close properly. Worth a watch before you start — the section on holding the backplate steady while you unscrew is easy to miss but saves a lot of bother.

1. Buy the right replacement tap before you start

Most UK outside taps are a standard hose union bib tap — a brass threaded body that screws directly into a wall-mounted backplate. Measure the thread on your current tap or take it to a builder’s merchant to match it. The vast majority are half-inch BSP, which is the UK standard, so you will almost certainly be fine with a like-for-like replacement.

It is worth buying a decent brass tap rather than the cheapest chrome thing on the shelf. Chrome-plated taps look smart for about a year in East Kent’s damp winters, then the plating bubbles off and the body corrodes underneath. A plain brass bib tap costs a few pounds more and lasts considerably longer. Pick up a roll of PTFE tape while you’re at it if you don’t already have one.

2. Turn off the water supply to the outside tap

This sounds obvious, but it catches people out. There should be an isolation valve on the pipe feeding the outside tap — usually under the kitchen sink or in a cupboard nearby. It is a small inline valve that you turn a quarter-turn with a flathead screwdriver. Once it is closed, open the outside tap to drain the last of the water from the pipe. If there is no isolation valve, you will need to turn off the main stopcock instead.

That said, if your property does not have an isolation valve on the outside tap supply, it is worth fitting one at the same time as you change the tap. It makes future maintenance much simpler and it is good practice to have one there anyway — especially if you want to isolate and drain the pipe before a hard frost.

3. Remove the old tap from the backplate

You will need two adjustable spanners for this. One grips the hexagonal body of the tap, the other holds the backplate still so it does not twist on the wall. This is the step most people skip, and it is the one that matters. If you just reef on the tap body without holding the backplate, you risk cracking the pipework or pulling the whole fitting off the wall.

Turn the tap body anticlockwise to unscrew it. It may be stiff, particularly if it has been in place for years. If it will not budge, a little penetrating oil around the thread and ten minutes’ patience can work wonders. Once it comes free, have a rag ready — there will be a small amount of residual water in the pipe even after draining.

4. Inspect the backplate and pipework

While the tap is off, have a proper look at the backplate. Check that the wall fixing screws are still tight, the thread in the body of the backplate is clean and undamaged, and that the pipe going through the wall is not corroded or kinked. If the backplate itself is damaged, replace it before fitting the new tap — it is a cheap part and not worth risking a leak for.

Give the thread a quick clean with a stiff brush or a bit of wire wool to clear any old PTFE residue or mineral deposits. A clean thread makes a better seal and means less effort winding the new tap in. Take a moment to check the wall around the backplate for any signs of damp, too. It is not uncommon to find a slow drip has been running silently behind the backplate for a while on older properties in Sandwich and the surrounding villages.

5. Wrap the new tap thread with PTFE tape and fit it

Wrap the threaded section of the new tap with PTFE tape — three or four turns is usually enough. Always wrap it in the direction of the thread, which is the same direction you will be tightening it. If you wrap it the wrong way, the tape just unravels as you screw it in and does nothing useful.

Screw the new tap into the backplate by hand first, then tighten with a spanner. Hold the backplate steady with your second spanner, the same as when you removed the old one. You want it firm but not over-tightened — brass threads are not especially hard, and if you gorilla it on, you risk cracking the backplate. The tap should end up pointing straight down or at a slight downward angle so water drains clear of the wall.

6. Turn the water back on and check for leaks

Open the isolation valve slowly, keeping an eye on the thread joint at the backplate as the pressure comes up. Give it a minute before declaring success. If you spot any seepage at the thread, close the isolation valve again, drain the pipe, and add another couple of turns of PTFE. A small drip at this stage almost always means not quite enough tape rather than a damaged thread.

Test the tap itself — open it fully, check the flow is strong, then close it and confirm it shuts off cleanly with no drip from the spout. If you fitted a new isolation valve at the same time, check that joint too. Once everything looks good, reattach your hose connector if you use one. And before the first cold snap of the year, remember to shut the isolation valve and open the outside tap to drain the pipe — it only takes a moment and it saves a burst pipe in January.

When to call a handyman

Call Richard if there is no isolation valve on the outside tap supply and you are not comfortable working from the main stopcock, if the backplate is cracked or the pipework behind the wall looks corroded, or if water has been seeping around the backplate and you suspect some damage to the wall or internal pipework. It is also worth getting someone in if the existing tap is soldered directly into copper pipe rather than screwed into a backplate — that is a different job altogether and calls for a bit more plumbing experience. Get in touch via the contact page and Richard can take a look.