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How to install an outside tap

Difficulty rating: Medium

These tasks may be tricky so will suit you if you're experienced in DIY, or simply love a challenge. Before you get started on any of our 'how to' guides, please take a moment to read through our DIY safety tips.

Installing a tap takes just half a day but you will need basic plumbing skills. Under current regulations you have to fit an isolation valve and a double check valve inside your home when you put in a new outside tap (see below for details). If you need to know more about the regulations talk to your water company or local council.

1. Turning off the water supply

  • Turn the isolation valve off if there is one on your cold water supply pipe where your new garden tap is to be connected (fig. 1a and 1b).
  • If there's no valve, turn off your main stopcock. This is fitted on the pipework and normally found either in the kitchen or where the mains water enters your house (fig. 2).
  • If you can't find the stopcock, turn off the water at the water company's valve under the cover in your street or front garden. You'll need a special long-handled spanner, available from plumbers' merchants (fig. 3).
  • Once the water supply is off, open the cold tap on your sink until the water stops running and the system is drained.
An example of a Push-fit Isolation Valve.
Figure 1a
An example of a Compression Isolation Valve with a tap.
Figure 1b
If there is no Isolator Valve, the main stopcock will have to be turned off.
Figure 2
If you can't find the stopcock, turn off the water authority's valve under the cover in the street or your front garden.
Figure 3

2. Drilling a hole through your external wall

  • If you're installing a new tap you need to bore a hole through your outside wall for the connecting pipework. It's easiest to make the new connection near an exposed cold water supply inside your house - near the kitchen sink, for example (fig 4).
  • Position your outside tap at least 250mm above the damp-proof course. Then mark the screw holes where your tap will be.
  • You'll need 15mm diameter pipe to connect the tap to the cold water supply inside the house. Position the hole for this about 150mm above where you've marked the position of the tap.
  • Before drilling the hole, run the pipe through a piece of 22mm diameter plastic pipe. This acts as a 'sleeve', which will prevent the pipe rubbing and water leaking out of the hole if the pipe bursts.
  • When drilling, make sure the hole is wide enough to take the plastic pipe sleeve's 22mm diameter.
  • Steadily drill through the wall with a heavy-duty power drill and a large masonry bit at least 325mm long.
  • Take out the core bit regularly to clear the loosened masonry and let the bit cool down.
Helpful hint...

Make it easy on yourself!

Buy a Homebase Outside Tap Kit - it's got all the parts you need and complete fitting instructions.

When drilling the hole through the outside wall, make the new connection near to an exposed water supply inside.
Figure 4

3. Pipework for the outside tap

  • With the supply turned off, cut through the cold water pipe directly below the exit hole you've drilled in the wall. Use a hacksaw or pipe slicer to do this and file the ends of the pipes smooth.
  • Remove enough pipe to fit a T-piece connector (fig. 8).
  • Connect one end of a short piece of pipe to the T-piece. Connect the other end to an isolation valve. This allows you to cut off the water supply to the new tap if you need to in the future (fig. 8).

Fitting an isolation valve

  • Isolation valves let you turn off the water to an individual appliance without having to turn off the whole water supply.
  • Fit the valve the right way round or it won't work correctly. There's an arrow on the valve showing the direction of the flow of water.
  • You can get two types of isolation valve: a push-fit valve (fig. 1a), which simply pushes into the ends of the pipes, and a compression valve (fig. 1b). Here we show how to fit a compression isolation valve.
  • When you've turned off the water supply, mark the section of pipe that needs removing to receive the valve (fig. 5).
  • Cut the section from the pipe with a pipe slicer or hacksaw. File the ends of the pipes smooth.
  • Now slide a compression nut onto each piece of pipe followed by the olives (fig. 6).
  • Push each end of the pipe into the fitting and tighten the compression nuts by hand.
  • Use a pair of pliers to hold the body of the valve and tighten the compression nuts about three-quarters of a turn.
  • When you turn on the water supply again, check for leaks. Tighten the compression nuts a little further if you have to.
  • Next you'll need another short piece of pipe to connect the isolation valve to a double check valve. 
Helpful hint...

When you're doing plumbing work, check if there's an isolation valve. If not, it's worth fitting one while you're at it. The valve isolates a particular part of the water system, so you can work on it without turning the water off at the mains.

 Double check valves
  • Water regulations say you must fit a double check valve to your outside tap pipework.
  • Double check valves stop water flowing back up a pipe the wrong way. This prevents contaminated water entering your drinking water supply.
  • For a new outside tap the valve must be fitted in your internal pipework, after the isolation valve (fig. 8).
  • You can replace an existing outside tap with one that already has a double check valve.
  • Double check valves are installed in a similar way to isolation valves. See 'Fitting an isolation valve' above.
  • After fitting the double check valve insert another short piece of pipe and an elbow (fig. 8). Then fit a length of pipe long enough to reach horizontally through the wall to the outside (fig. 8). When it's through the wall, cut the pipe to leave about 25mm protruding.
  • Finally, you'll need to cut a piece of pipe that reaches from the horizontal pipe protruding from your outside wall down to the position of your tap.
  • These pipes are connected using another elbow joint.
  • Connect all the parts together and tighten the joints with two adjustable spanners. You can tighten joints more if they leak when the water supply is turned back. But don't overtighten.
Helpful hint...

Use copper or plastic pipes for your outside tap. Copper looks better and lasts longer but plastic is easier to work with. Only use push-fit or compression connectors. They're much simpler to fit than soldering, and solder doesn't go well with water. 

Use the body of the isolation valve as a guide to mark the exact section of pipe that needs removing.
Figure 5
Slide a compression nut and olive onto each side of the pipe.
Figure 6
Once the tap plate is firmly attached to the wall, screw the tail of the tap into the elbow join.
Figure 7
An isolation valve and a double check valve must be fitted between the T-piece and hole to the outdoor tap.
Figure 8

4. Attaching the new outside tap

  • Drill the fixing holes for the tap's wall plate, insert plugs and screw the tap plate to the wall. Screw the tap tail into the elbow joint (fig. 7).
  • Use plastic retaining clips for the pipes on the inside wall to stop the pipes vibrating and knocking against it.
  • Seal around the pipe hole in the wall with an expanding foam filler or sealant.
  • Finally, turn the water supply back on and check for any leaks.
  • Tighten joints if you need to and then you're ready to go.

Tools for the job

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