I have a water pump with three wires – green/yellow(ground), the other two are white and green. Which is live and which is neutral?

Ken, I’m guessing that you must be writing from outside the EU – as far as I know, none of the EU member states has used that kind of wiring. In fact, I’m not sure that any of the major international standards uses it!

One of the simplest ways of finding out which wire is live is to obtain a mains testing screwdriver (also known as an electrician’s screwdriver) – it shouldn’t cost more than a couple of pounds. This looks like a normal screwdriver except that there’s a small bulb in the handle (which has a small metal patch at the top), and the shaft is usually insulated, with only the blade exposed. The screwdriver should have some kind of marking to let you know for what voltage range it may safely be used.

WARNING: DO NOT use a mains testing screwdriver for a mains circuit with a voltage higher than the maximum voltage indicated!

To test for a live current:

First of all, make sure that the appliance you’re testing is switched off. (If it’s switched on, then current is likely to be flowing through both wires, so you’ll be none the wiser.)

You’ll also need to have access to the bare wires or – better – to the terminal screws securing them to the appliance.

Then hold the screwdriver so that the handle’s between your thumb and middle finger and your index finger is pressing on the metal patch, and touch it to ONE of the two wires or screws.

WARNING: DO NOT let the blade touch more than one wire or screw at once, or form a bridge between the wire and the earth/ground connection – at the very least, you’ll melt the blade of the screwdriver, and possibly far worse.

When the blade of the screwdriver contacts the live wire or terminal, you should see the bulb inside the handle glow (usually reddish-orange). But DON’T assume that if the first wire glows, the second must be neutral. There may be a fault in your wiring. So always check both wires – or all three, if there’s an earth wire too.

Likewise, if neither wire glows, then there may be a fault with your tester – so ALWAYS test your tester before and after use, for instance on a socket that you know works.

Another way of checking is to trace the wiring back to the consumer unit (“fuse box”) and checking where it’s wired up to at that point. But make sure you do it thoroughly – crossed wires at any point (for example, an incorrectly wired socket or junction box) could mislead you into thinking that a wire is neutral when it is, in fact, live. So keep that mains tester handy!

And to avoid confusion in future (for instance, if you sell the house on) it would be as well to have the wiring replaced, by a competent electrician, with wiring that complies with the local standards – or, if there is no local standard, at least an internationally known one like the EU or US standard.

Whichever way you’re doing it, you’ll need to be aware of the correct colour coding for the cables when connecting up the socket. You can find out about that on our Electricity cable colour coding page.

Running a spur from another socket

This is a handy solution if all you need to do is run a cable along the surface of the wall or worktop, for instance in a shed or garage or anywhere else where you’re not that bothered about appearances.

First, turn off the power to the ring circuit at the consumer unit!

Next, remove the screws securing the faceplate of the socket you’re proposing to run the spur from, and have a look at the back of the socket to see how many cables it’s connected to. If there are two cables running to the socket, then you’re in business. (If there’s only one, then the socket is probably already at the end of a spur; if there are three, then the socket’s already providing a spur connection.) Undo the terminal screws and remove the wires from the socket.

Having fitted your new socket, wire it up in the usual way and run the cable to the existing socket. You may find that you need to make the existing cable entry hole larger to accommodate the spur cable, or else that you need to knock out another hole. Once you’ve done that, feed the cable into the socket box, strip off the ends of the neutral and live conductors, slip a length of green-and-yellow insulation onto the earth wire, and then twist the ends together with the ends of the existing cables. Insert the wires into the appropriate terminals (again, see our Electricity cable colour coding page if you’re in any doubt) and tighten the screws. Then refix the socket to the socket box, turn the power back on at the consumer unit, and test the new socket.

Connecting a socket to the ring circuit via a junction box

This is probably the best option if there are no handy sockets nearby to run a spur from, or if adding a spur would mean disturbing plaster or having an exposed cable run where you’d rather have it concealed.

You’ll need a junction box with at least three cable entry holes (two for the ring circuit cable, one for the spur to the socket); depending on the type of box you have, you can either rotate the cover so that exactly three holes are available, or knock three blanks out of the knock-out holes in the moulding. Lift a floorboard up near where you want the socket to be, and where you can run the ring circuit cable into the box without putting it under strain. Fix the junction box securely, either directly to one of the joists or by adding a fixing platform between two of them. (If you’re using a fixing platform, it’s better to put the cable over the platform beforehand so that you don’t have to cut the conductor wires.)

Turn the power off at the fuse box or consumer unit!

Put the cable across the junction box and mark off how much cable sheath you need to remove (ensuring that you don’t remove so much that the conductor wires are exposed. Then slit it down the middle, taking care not to cut into the insulation for the live and neutral wires, and peel it back. Strip off just enough insulation from the live (red, or brown in modern installations) and neutral (black, or blue in modern installations) wires to fit the exposed wires into their respective terminals. Cut the bare earth wire and put lengths of insulating sleeve (green-and-yellow) onto each end.

Take out the screws from all three terminals and lay the wires across them. The earth wire should go into the middle terminal. Then, having fitted your new socket, wire it up in the usual way and run the cable to the junction box. Feed the cable into the box, strip off the ends of the neutral and live conductors, slip a length of green-and-yellow insulation onto the earth wire, and then insert the ends into the appropriate terminals (again, see our Electricity cable colour coding page if you’re in any doubt). Tighten the screws. Then replace the junction box lid. Clip the cables to joists to reduce strain on the terminals, and replace the floorboards. Turn the power back on at the consumer unit and test the new socket.

Adding a socket directly into an existing ring circuit

This is only really an option if your existing wiring has plenty of slack. Given that it’s undesirable to leave cable under strain – as is likely to be the case if you pull up all the slack – we wouldn’t normally recommend this one.

Turn the power off at the fuse box or consumer unit!

Pull a loop of the ring main cable up to the new socket and feed it into the socket box through an entry hole. Cut it. Strip back the sheathing of both ends and the insulation of the live and neutral wires. Fit insulation sleeves onto the earth wires.

Twist the matching wires together. Fit each of the twisted ends into the appropriate terminals on the socket (again, see our Electricity cable colour coding page if you’re in any doubt). Tighten the terminals.

Replace the socket faceplate and screw it tight. Turn the power back on at the consumer unit and test the new socket.

In the United Kingdom, the regulations that came into force on 1 January 2005 mean that all domestic cabling installed after that date has to conform to the following colour code:

• Live: brown
• Neutral: blue
• Earth: green/yellow
  (In practice, the earth wire is usually bare; the person doing the work has to fit a length of green/yellow sleeving over any exposed parts of the wire)

This corresponds to the colour codes in the flex that’s been used for domestic electrical appliances for the last few decades.

As you’d expect, though, the vast majority of houses built before that date are still wired with cable using older colour coding. The cable will almost always be coded as follows:

• Live: red
• Neutral: black
• Earth: green/yellow (or green, in some very old installations).

So when making your connections, remember to connect only these together:

RED – BROWN – Terminal marked L

BLACK – BLUE – Terminal marked N

GREEN – GREEN/YELLOW – Terminal marked E or

The good news is that in most cases it’s a relatively easy job to do this, and – at the time of writing – you don’t need to notify the job to the council under Building Regulations, as long as you’re adding the sockets to an existing radial circuit, ring circuit or spur and not direct to the consumer unit.

NB – There are important exceptions to this!

• Work carried out in a kitchen, bathroom or outdoors must ALWAYS be notified.
• The only sockets allowed in a bathroom are low-power ones for electric shavers, and there are stringent regulations as to where they may be located.

We strongly advise against undertaking your own electrical work in any of these locations.

In any event, it’s a sensible step to get your work tested and certified for safety afterwards – to ensure that your building and contents insurance is still valid and that the work doesn’t cause a hitch if you come to sell the house.

You can choose two basic ways of mounting your new socket: surface-mounted or flush-mounted.

Flush-mounted sockets

Flush-mounted sockets are a little more tricky than surface-mounted ones because you’ve got to cut away part of the wall to fit the metal mounting box inside. But they’re much tidier.

Plasterboard

If you’re fixing to plasterboard, it’s relatively straightforward. Draw or trace an outline of the box where you’re planning to fit it, and drill a hole in each corner big enough to fit a padsaw blade into. Then cut along the lines of the outline and remove the plasterboard. Remove the cable entry hole you’re using (probably the bottom one, unless you’re running the cable from the ceiling) and fit a rubber grommet, then feed in a 75mm (3″) loop of cable.

Clip dry-wall fixing flanges onto the sides of the box. Put one side of the box into the recess, then (being careful not to drop the box!) ease the box into position so that both flanges are behind the plasterboard and the box fits nicely in the hole. Finally, wire and fit the socket (see below).

Lath-and-plaster

Slightly more complex because of all the wood you’ll need to cut through.

If possible, try to position the socket over a stud or a nogging. You may find you have to chisel a notch into the stud to get the box flush with the surface of the wall; keep trying the box against the stud until you’ve removed enough wood. Fit a grommet over the cable entry hold and feed a 75mm (3″) loop of cable into the box, then screw the box to the stud or nogging and wire the socket.

Otherwise, you’ll have to remove a lot more lath-and-plaster to enable you to fix a nogging between two studs – and you’ll have the problem of making good the plasterwork afterwards.

Masonry

This is a laborious task rather than a genuinely difficult one. You’ll need to chop away the brickwork, not just to make the hole for the socket box, but also to create a “chase”, or channel, for the cable by cutting away the plaster down to the brickwork.

When making the hole for the socket box, the best way is to cut away the plaster where you intend to position the socket, then drill several holes in the brickwork to a depth such that the box will sit flush with the wall. Try the box in the hole. It it’s a good fit, make marks through the fixing holes and remove the box, then drill the wall and fit No.8 plugs. If it’s loose or if the hole’s too deep, remove the box again and put in a little filler, then replace the box so that it fits correctly. After 10 minutes, carefully take the box out again and allow the filler to set, then drill the wall and fit plugs as above.

Choose which cable entry hole you’re going to use and remove the blank, fit a grommet, feed a 75mm (3″) loop of cable into the box, then screw the box to the wall. Plaster around the box and over the cable; once it’s set, you can wire and fit the socket.

Wiring and fitting the socket

This is straightforward. You’ll need to use new-style wiring cable with a brown insulated live wire and a blue insulated neutral wire. The bare wire in the middle of the cable is the earth wire; you should insulate this yourself with the correct green-and-yellow sleeving.

The brown wire goes into the hole marked “L”; the blue wire goes into the one marked “N”, and the earth wire goes into the one marked with the letter “E” and/or the earth symbol. Strip off just enough insulation to ensure that a connection is made; if you strip away too much, then either snip the wire shorter or fold it back on itself. Make sure the terminal screws are tight.

You may have to bend the individual wires (which are quite stiff) to allow the faceplate of the socket to close. When you’ve done that, tighten each fixing screw bit by bit until the faceplate is securely fixed to the wall or the box.

Once you’ve done that, you’ll be ready to connect your socket to the mains.

Surface-mounted sockets

Surface-mounted sockets are much more straightforward to add as all you have to do is drill a couple of holes and fix the box to the wall using screws and wall plugs, though they can look a bit unsightly. We’ve got another article that tells you how to mount sockets on the surface of the wall.

The good news is that in most cases it’s a relatively easy job to do this, and – at the time of writing – you don’t need to notify the job to the council under Building Regulations, as long as you’re adding the sockets to an existing radial circuit, ring circuit or spur and not direct to the consumer unit.

NB – There are important exceptions to this!

• Work carried out in a kitchen, bathroom or outdoors must ALWAYS be notified.
• The only sockets allowed in a bathroom are low-power ones for electric shavers, and there are stringent regulations as to where they may be located.

We strongly advise against undertaking your own electrical work in any of these locations.

In any event, it’s a sensible step to get your work tested and certified for safety afterwards – to ensure that your building and contents insurance is still valid and that the work doesn’t cause a hitch if you come to sell the house.

You can choose two basic ways of mounting your new socket: surface-mounted or flush-mounted.

Flush-mounted sockets

Flush-mounted sockets are a little more tricky than surface-mounted ones because you’ve got to cut away part of the wall to fit the metal mounting box inside. But they look much tidier. You can see how to do it in our article on mounting flush-mounted sockets.

Surface-mounted sockets

Surface-mounted sockets are simple to install; you simply take the plastic box and screw it to the wall using screws and wall plugs. The disadvantage is that they stick out into the room a bit – which can be inconvenient if, say, you’re planning to install them over a worktop where space may be at a premium.

Just knock out the fixing holes in the back of the plastic box, then hold the box up square against the wall and make a mark on the wall through each hole. Drill holes and plug them with No.8 wall plugs. Break away the piece of plastic covering the cable entry hole you’re planning to use (the one in the back if the cable’s buried in the wall, one in the side if it’s surface-run). Push a loop of cable of about 75mm (3″) length into the box, then fix the box to the wall using countersunk woodscrews. Finally, wire the socket (see below).

Wiring and fitting the socket

This is straightforward. You’ll need to use new-style wiring cable with a brown insulated live wire and a blue insulated neutral wire. The bare wire in the middle of the cable is the earth wire; you should insulate this yourself with the correct green-and-yellow sleeving.

The brown wire goes into the hole marked “L”; the blue wire goes into the one marked “N”, and the earth wire goes into the one marked with the letter “E” and/or the earth symbol. Strip off just enough insulation to ensure that a connection is made; if you strip away too much, then either snip the wire shorter or fold it back on itself. Make sure the terminal screws are tight.

You may have to bend the individual wires (which are quite stiff) to allow the faceplate of the socket to close. When you’ve done that, tighten each fixing screw bit by bit until the faceplate is securely fixed to the wall or the box.

Once you’ve done that, you’ll be ready to connect your socket to the mains

If a leasehold flat is not connected to the incoming earth, who is responsible for connecting it, the landlord or leaseholder?

This is not as straightforward a question as it might appear, because it depends to an extent on what sort of earth connection is possible. This in turn depends on where the property is, and how the mains supply reaches it.

Types of earth connection

There are three types of earth connection commonly in use for domestic installations in the UK:

TN-S (earth neutral separate): This is probably the most common installation, where the distributor (the electricity company) provides separate earth and neutral connections back to the substation.

TN-C-S (earth neutral combined/separate): In this variation on TN-S, the electricity supplier provides a combined earth and neutral connection, but separates them at the point where they enter the domestic installation. This type of installation is also known as PME, or Protective Multiple Earthing.

T-T (earth to earth): In this type of installation, the electricity company does not provide an earth connection at all – usually because the distributor cannot guarantee the connection back to the substation, for example where the power cables are run overhead to the property and there’s a risk of the earth becoming disconnected somehow or even getting stolen. Earthing has to be provided locally by connection to the ground, using earth rods, earth plates or perhaps underground structural metalwork where this exists.

So who’s responsible?

In the case of the first two types of installation, responsibility for providing an earth connection to the consumer unit (fusebox) lies with the electricity company, and there should already be an earthing block present.

In the case of the T-T earth connection, responsibility lies with the consumer, not with the electricity supplier. So unless the terms of the lease explicitly state that the landlord is responsible for ensuring the electrical supply, the presumption has to be that the leaseholder (i.e. the person who’s actually consuming the electricity) is responsible for it – and thus for ensuring that the earth connection meets BS 7671, the IEE Wiring Regulations. Having said that, it’s quite common – especially in the case of council housing – for the landlord to be responsible for all communal wiring, but for the leaseholder to be responsible for the wiring which serves only their own part of the building.

If you’re in a leasehold flat, then your best bet is probably to check first of all to see what your lease says, if anything; and then to check with other leaseholders to see what their earthing arrangements are. If their earth connections are supplied by the electricity company, then in all likelihood yours should be too and you should take it up with the company. Otherwise, it may be that there’s a communal earth plate or rod (or set of rods) and it may be as simple as getting an electrician to provide a connection to the communal earth wiring.

NB – electrical work of this nature MUST be notified to your local authority’s Building Control Department and the work certified by a Competent Person. In the case of a leasehold flat, with the obvious potential liability towards other leaseholders as well as the freeholder, we STRONGLY recommend that you get a firm that’s a member of a Competent Person scheme to do the work.

I just got an electric shock off the kitchen sink. How did that happen? The sink isn’t an electrical appliance. I don’t understand it.

This is a problem with earthing – the connection with the ground which ensures that any current which doesn’t follow its intended circuit flows harmlessly to the ground, without using other conductors (like your body) as a shortcut.

The problem arises when exposed metal (sinks, pipes, metal casings) is somehow connected to a live electrical source. This can happen more easily than you might think; water is a good conductor of electricity, and so are damp or wet substances like plaster or grouting. The current involved is usually low, but enough to give you an unpleasant tingle in the part of your body that’s in the circuit – and if the current’s high, or you’ve got bare feet, the shock can be far worse or even fatal, especially if you’re standing on a wet floor!

(The current doesn’t even necessarily have to flow to the floor, if you’re touching two different metal objects – say, a kitchen tap and a sink – and one is earthed while the other isn’t.)

Fortunately, the problem’s relatively easy to stop; ensure that there’s a good earth connection between all pipework and other metal objects which runs to the earthing block in your electrical consumer unit. (The technical term for this is electropotential bonding or supplementary bonding.)

Pipes can be fitted with clamps (which look something like jubilee clips). First clean an area of the pipe with steel wool to make sure there’s a good connection, then fix on the clamp. After that, fix the earth wire (which should have a green-and-yellow insulating sleeve to identify it) to the clamp.

Baths and basins should have an earth tag, to which the earth wire can be connected using a nut, bolt and metal washers. Again, make sure the connection is clean and free of paint or enamel.

Fixed electrical appliances will likely have their own earth connection. If they have a metal case, the case should also be connected to the earth.

It may be that the wiring is already there and that one of the connections has either worked loose or corroded. If so, all you’ll need to do is clean it up or replace the corroded parts.

However, because this is a safety issue, we strongly recommend that you have the work tested by a Competent Person firm of electricians or other qualified person – and if you have any doubts at all about your ability to do the work yourself, get a professional electrician to do it. (See our article on domestic electrical repairs for more details.)

Notification

Under the new legal requirements, the local authority’s Building Control Department do not need to be notified if the work is straightforward repair, replacement or maintenance work (generally, anything involving like-for-like replacement is fine). Nor do they need to be notified if the work is an alteration or addition to existing ring-main or lighting circuits unless it’s in a kitchen or bathroom, or outdoors.

For most other things, they will need to be notified that the work is to be done, and the work will need to be inspected and certified after completion.

If in doubt, ask the Building Control Department.

Inspection and certification

If you’re undertaking a notifiable repair yourself, or the person undertaking the repair isn’t a member of one of the Competent Person schemes of self-certification, then you’ll need to arrange for the work to be inspected and certified by the Building Control Department or one of their approved inspectors.

For that reason, it will usually be easier to get a firm that’s a member of a Competent Person scheme to do the work. The five currently operating schemes (as of November 2007) are run by:

• BRE Certification
• BSI (British Standards Institution)
• ELECSA
• NICEIC (NB Zurich Certification are now part of NICEIC)
• NAPIT

Even if the work done is not notifiable, it may be worth getting a Competent Person firm to do the work anyway – by doing so, if you ever come to sell your house you’ll be able to show that the work has been done to the approved standard.