Earthing of water supply - Part P Building Regulations


Postby elsbeth1962 » Fri Aug 27, 2010 12:51 pm

I am advised that I have no earthing to my water supply. I live in a victorian terrace with a kitchen extension added to the back of the house in 1980s/1990s. The stopcock is in the kitchen extension beneath the sink/work units. Mains / consumer unit is based in cellar, single chamber under the front of the house, meaning that to earth the stopcock we would have to run wire from the cellar / consumer unit, through a back room and out into the kitchen. Only way to do this is to have wires above floor, along skirting in trunking which would be very unsightly and not easy to install. Wiring cannot go under concrete floor and am not prepared to take laminate up / have costly disruption to the house as it seems disproportionate. Have had advice from electrician that he can earth the nearest water pipe inside the house as the next best alternative and list this as a deviation on the certificates. Will this be enough to satisfy the regs or am i really expected to tear the house apart to get to the stopcock? Any advice much appreciated!
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Postby stoneyboy » Fri Aug 27, 2010 9:33 pm

elsbeth1962,
The regulations are specific in that all incoming supplies should be bonded together at the points where they enter the house using 10mm earth cable. No alternatives are specified.
How about running the earth cable on the top or bottom of the skirting and painting it the same colour as the skirting.
If you want to go with your electricians solution he will have to ensure continuity of the pipework throughout the house - do make sure he is registered to certify the work especially the deviation.
end
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Postby ericmark » Fri Aug 27, 2010 10:51 pm

To be safe is different than to follow regulations. We are told one meter of plastic pipe will isolate and where plastic piping is used except for where visible there is no need to bond it. And it says in regulations one should bond the main metallic water pipe (extraneous-conductive-part) and "extraneous" means coming from the outside. So where the supply is metal then you would need to bond but where the supply is plastic then there is not really a problem.

To use the pipework to conduct the earth connection was all well and good in years gone by as pipes were steel, copper or lead but today we use a lot of plastic and it is all too easy for a plumber to some time in the future to replace a metal pipe with plastic.

This should have been picked up when the extension was added and on each PIR which was carried out every 10 years or change of occupant so in theory you should have been aware of this for some time. However until 2004 when Part P became law many items were missed like this.

Two methods seem to be open to reduce the risks. All circuit RCD protection and plastic pipes however the plastic at least 1 meter would need to be before the stop cock unless the stop cock is plastic as other wise under fault conditions you could get a belt off the stop cock.

The law is a little odd. BS7671:2008 is not law but may be used in a court of law. Part P is law but does not say BS7671 must be followed it just says that is one way to ensure complies. Regulation 411.3.1 does not make it easy with phrases like "Simultaneously accessible exposed-conductive-parts shall be connected to the same earthing system individually, in groups or collectively." and it is down to interpretation and since it says:-
411.3.1.2 Protective equipotential bonding
In each installation main protective bonding conductors complying with Chapter 54 shall connect to the main
earthing terminal extraneous-conductive-parts including the following:
(i) Water installation pipes
(ii) Gas installation pipes
(iii) Other installation pipework and ducting
(iv) Central heating and air conditioning systems
(v) Exposed metallic structural parts of the building.

Most people will not want to complete a completion notice unless the water is bonded but do note the word "extraneous". At the end of the day your electrician must consider if the system is safe and it's his signature on the certificate and does not really matter what we say it is what he says that goes.

Remember to the phrase "It's been like that for years" one answers you have has loads of time to correct it then.
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