water main earth

12 Nov 2005
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United Kingdom
Hallo Sparkies,

I have just replaced my watermain. It is now run in plastic. Previously it was 15mm copper and was earthed to an earth block by the meter. Two adjoining pipes supplying hot and cold water to a downstairs sink were cross bonded to each other and then to the incoming water main.

What should I do now, should I connect these remaining copper pipes back to the old earth lead which is still hanging about so to speak or, should I just leave them as they are. Looking at the rest of the installation overall if I leave it, although there is cross bonding at various points, including on the central heating flow and return there would be no connection back to the incoming supply at the meter which would seem to be pointless.

The gas main has it's own earth connection back to the same earthing block

At the supply head the earth is connected to the neutral
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So you have a plastic incoming water pipe but the rest of the water pipes are still copper? In this case you still need to main bond the pipe at the point where it changes from plastic to metal.
That's way up in the loft. It runs in Plastic for about 99% of the way until it reaches a point about half a meter from my water tank.

To do this I would have to run about 6 meters of earth cable
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IEE: To bond or not to bond

If the incoming pipes are made of plastic, but the pipes within the electrical installation are made of metal, the main bonding must be carried out. The bonding being applied on the customer side of any meter, main stopcock or insulating insert and of course to the metal pipes of the installation.

The connections of the bonding wired to the pipes has to be made with a proper clamp to BS 951 complete with the label “SAFETY ELECTRICAL

If the incoming services are made of plastic and the pipework within the building is of plastic then no main bonding is required. If some of the services are of metal and some are of plastic, then those that are of metal must be main bonded.

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