How to Swap a Socket

rewiring a double plug socket
(Image credit: Jeremy Phillips)

You can double your socket power in a weekend just by swapping your single outlets for doubles. An electrician will charge £30 to do the same job for you. Multiply that by the number of single sockets in your house and you’ll see how much you can save by doing it yourself. If you’ve already got double sockets then this guide will show you how to change the inevitable cracked, burnt or paint-spattered parts for fresh new ones. Also covered in this piece is how to add a new socket into the ring main another job an electrician will be happy to charge up to £80 for.

If you are wondering whether you can swap any single socket for a double, then the answer is yes, providing the existing socket is the only one on that spur (wire feed) from the ring main. To check this out, do the test in Step 6. How many new sockets can you add? In theory you can double the amount of outlets by taking a spur off each of the existing sockets or the junction boxes that feed them. You must check that the socket you intend to spur from is part of the ring main (see the test in Step 6).

  • Insulated screwdriver
  • Mains voltage/continuity tester
  • Drill
  • Hammer
  • Bolster chisel
  • Pad saw or hacksaw blade
  • Wire strippers

Materials needed:

  • 2.5mm twin and earth cable
  • Twin socket
  • Twin socket steel box for flush fit or plastic box for surface mount
  • Ready-mixed plaster


1. If any of your sockets are burnt, then they need to be replaced. Steps 3, 4, 11 and 12 will show you how.

2. Placing too much demand on a single outlet often causes burnt sockets. If this is all too familiar, read on and learn how to swap your singles for doubles.

3. Before you start work, isolate the ring main at the consumer unit or fuse board. Some units feature a circuit breaker that just needs to be switched off. If you have an older-style fuse board, switch off the main power, remove the appropriate fuse (hopefully labelled ring or main ring) before switching the unit back on again. Just isolating the ring main means there’s still power to the lights – handy if you’re working in a dark corner of the house.

4. Many older houses feature more than one fuse board or consumer unit so you can’t always be sure that you’ve isolated the correct part of the circuit. To check, plug an appliance into the socket you intend to work on. If you use a radio for this test, check that any batteries have been removed first, otherwise you could spend a fruitless day searching for a non-existent power supply.

5.With the circuit isolated you can safely undo the screws on the front of the socket. If there’s just one wire per connector (earth, live and neutral) it means that the socket has already been spurred off another; you can change this into a double socket but you can’t spur off it to supply a new outlet. Two wires going into each connector indicates that the socket is either part of the ring main or that it is one of two sockets fed by the same spur. If you plan to swap a single socket for a double or add a new spur, you must make sure that the outlet is part of the ring main. To check, you need to run the continuity test in the next step.

6. Go round the house and switch off and unplug (if possible) any electrical equipment fed from the ring main. At the socket, undo the screw that holds the live (red or brown) wires and touch one of them with a probe from a mains voltage tester set on continuity mode. Touch the other probe of the tester to the neutral terminal (labelled N with black or blue wires). Repeat this with the other red or brown wire. The unit’s buzzer or light should not come on when you are testing the wires this way. Touch one probe on each of the red or brown wires. If the tester buzzes or lights up this means that the socket is part of the ring main. If you are swapping a single socket for a double, remove all the wiring from the old socket. If you plan to spur a new socket from this one, run wire back from the new sockets position under floorboards or through conduit along a wall.

7. If you are swapping a single socket for a double, you can use a surface-mounted plastic box or a steel box that is fitted into the wall giving a flush finish. In this instance were fitting a steel box in place of the old single socket box. Flush-mounted boxes can be fitted in traditional plaster over brick walls like this and in more modern plasterboard, over studwork walls. In both cases it makes sense to use the existing hole as part of the new opening. Place the box in position and draw round it.

8. Use a bolster chisel and hammer to break out the plaster and brick (be very careful not to cut through the cable). Old plaster has a nasty habit of coming away in large chunks so be prepared to do some repair work afterwards. Plasterboard walls are much easier to cut to size with a pad saw or a hacksaw blade.

9. Take a very close look at the cables coming up through the wall. If there are any signs of damage, including burning, cuts or crumbly insulation, they’ll need to be replaced back to where they join the ring main – a laborious but essential job.

10. The metal boxes used for flush-mount fixings have a series of pre-punched holes for the cable to feed through. Select the appropriate one and press it through with your thumb or the end of a screwdriver. Push the box into the wall, pull the wires through the hole (ideally through a grommet), drill the mounting holes and fix in place.

11. Fit the wires into the back of the socket. Live and neutral are marked with an L and N respectively while the earthing point is normally a metal tag signified by an E or three short horizontal lines topped by a vertical line. We’ve used the new colour-coded wires which are: live, brown; neutral, blue; and earth, yellow with a green tracer. There’s a good chance that you’ll have the old colour-coded wires which are: live, red; neutral, black; and earth, green with a yellow tracer. Its perfectly acceptable to use the two types together as long as all the wire is in good condition. If you are fitting an extra socket you’ll only have one set of wires to fit in the back of the unit.

12. Press the socket back into place taking care not to trap any of the wires in the process. Tighten the screws, put the power back on and plug something in to test that everything is working OK.