Electrical safety

Q: Our old iron main water pipe was leaking, so a plumber replaced it with a new plastic pipe. However, the original pipe was also acting as the ground wire for the electrical system in the house, so we had to make another ground wire. Should the plumber be aware of this situation, as I'm concerned it could be a safety issue in other old houses like mine?

A: In modern houses, the electrical system must be earthed independently of any metal water or gas pipes. However, in older houses, use of the plumbing system as an electrical earth is a common occurrence. A competent tradesperson should be aware of the electrical issues regarding any galvanised or copper pipes they are renewing or disconnecting, whether for water or gas, either in the building or connecting to it.

Most plumbers work with, or know, an electrician who can advise on the requirement of correct earthing for a building.

The hazard does not stop at the pipe being used as an earth. It is also very possible that a steel or copper pipe is subjected to stray currents from the house, or even from neighbouring houses or other sources. This could be a serious hazard for those cutting or disconnecting the metal pipe without using a bonding strap to prevent the stray current going to earth through the tradesperson working on the pipe.

You will often see permanent bonding straps across parallel pipes on a building. It is important not to interrupt these, and a reputable plumber should advise the customer to call their electrician in this instance.