Earth Bonding Explained: Gas, Water and Why an EICR Checks It

Earth bonding is one of the things an electrician checks on every EICR, and missing bonding is one of the most common faults we find in older London homes. It is easy to miss, because the cables are small and often hidden under the sink or behind the gas meter. This guide explains what it is, why it matters and what to do if your report flags it.

What main bonding is

Main protective bonding is a green and yellow cable that connects incoming metal pipes, usually the gas and water services, to the main earthing terminal near your consumer unit. It is normally clamped to the pipe close to where it enters the building, with a small label that says "Safety electrical connection, do not remove".

Why it matters

If a fault makes metal pipework live, the bonding keeps the pipes and other earthed metal at the same voltage, so you cannot get a dangerous shock by touching a tap and an appliance at the same time. Without it, the protective devices in the consumer unit may not keep you safe in every fault.

What an EICR usually finds

• Bonding missing altogether, often after a plumber has replaced a pipe in plastic and removed the clamp.
• Bonding cable too small for the supply, common in older homes.
• Clamps loose, painted over or fitted to the wrong side of the meter.
• Bonding to the gas pipe fitted too far from the meter.

Missing or inadequate main bonding is usually coded C2, meaning it is potentially dangerous and must be fixed. Our guide to what a C2 means on an EICR explains the codes.

What about bathrooms?

Older homes often have extra bonding cables in the bathroom, known as supplementary bonding. Under current rules this can usually be left out where all bathroom circuits have RCD protection and the main bonding is right. Our guide to bathroom electrics and zones covers the details.

Fixing it

Adding or upgrading main bonding is normally a small job, often done in a couple of hours, though it can take longer where pipes are hard to reach or cables need to run through finished rooms. After the work you should receive a certificate, and if it was raised on an EICR, confirmation that the fault has been put right.

Book a check

Energy North Ltd covers North, East and West London with City & Guilds certified electricians, and can usually attend within 48 hours. See our EICR service to have your bonding and earthing checked.