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Is this method of earthing a water pipe permissible?

Arran Cameron

A house has the main earth terminal block located next to the electricity supply cable in a cupboard in the living room. The water supply is a blue MDPE pipe located in the kitchen that transitions to a copper pipe about 2m before the stop tap.

About 1m away from the earth terminal block are a pair of copper central heating flow and return pipes. These same two pipes are located right next to the copper water supply pipe in the kitchen.

The easiest, and most economical on cable, method to earth the pipes is to connect the earth terminal block to the central heating pipes in the living room, then connect the central heating pipes to the water supply pipe in the kitchen.

Is this permissible, or must a long length of earth cable be installed under the floorboards connecting the earth terminal block to the water supply pipe?

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    It is a somewhat muddled situation - 544.1.2 specifies the bond be on the consumer's side of the position of a possible insulating joint (i.e. at the meter) so that the whole purpose of the insulating joint (IJ) isn't defeated and the gas people don't end up with diverted N currents flowing around their pipework when they don't want that. On the other hand basic physics wants all internal pipework bonded where it is (or at risk of being) extraneous - logically including any metallic section between where it comes out of the ground or enters the building, and the meter (where the meter is internal). You won't find PE gas pipes internally as they're not sufficiently fire resistant for the gas regs.

    For me if there's any doubt as to the presence (or future reliability) of an IJ - then bond after the meter and ensure that any metallic pipework before the meter is covered with insulating material so it can't be touched (or can't introduce a potential into the installation, in definition terms).

    We are departing somewhat from the original question however. As has already been said, 543.2.6 lays down the requirements for using an extraneous-conductive-part as a protective conductor. In a domestic situation (iii) (precautions shall be taken against its removal) is likely to be hard to achieve - as even the removal of a small section of pipe - e,g. to insert a plastic fitting - during alterations or repairs would be a problem. In some controlled environments - e.g. where there are permits-to-work and everything is organised though a single authority who oversees all work undertaken, you could have something written into the appropriate procedures and have some confidence in it being taken account of, but in a domestic situation where plumbers are likely to work without any detailed technical control, I would be far more dubious. Even the ordinary "safety electrical connection - do not remove' labels don't seem to be properly understood by a significant number of domestic plumbers, so you'd have a hard job to convince me that any kind of labelling alone would suffice.

       - Andy.

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  • 0

    It is a somewhat muddled situation - 544.1.2 specifies the bond be on the consumer's side of the position of a possible insulating joint (i.e. at the meter) so that the whole purpose of the insulating joint (IJ) isn't defeated and the gas people don't end up with diverted N currents flowing around their pipework when they don't want that. On the other hand basic physics wants all internal pipework bonded where it is (or at risk of being) extraneous - logically including any metallic section between where it comes out of the ground or enters the building, and the meter (where the meter is internal). You won't find PE gas pipes internally as they're not sufficiently fire resistant for the gas regs.

    For me if there's any doubt as to the presence (or future reliability) of an IJ - then bond after the meter and ensure that any metallic pipework before the meter is covered with insulating material so it can't be touched (or can't introduce a potential into the installation, in definition terms).

    We are departing somewhat from the original question however. As has already been said, 543.2.6 lays down the requirements for using an extraneous-conductive-part as a protective conductor. In a domestic situation (iii) (precautions shall be taken against its removal) is likely to be hard to achieve - as even the removal of a small section of pipe - e,g. to insert a plastic fitting - during alterations or repairs would be a problem. In some controlled environments - e.g. where there are permits-to-work and everything is organised though a single authority who oversees all work undertaken, you could have something written into the appropriate procedures and have some confidence in it being taken account of, but in a domestic situation where plumbers are likely to work without any detailed technical control, I would be far more dubious. Even the ordinary "safety electrical connection - do not remove' labels don't seem to be properly understood by a significant number of domestic plumbers, so you'd have a hard job to convince me that any kind of labelling alone would suffice.

       - Andy.

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