What is earth bonding?
By Azzeddine Kebbi, NAPIT-registered electrician and director of Kebbi Electrical Services · Updated 10 November 2026
Earth bonding is the green-and-yellow cable that connects metal gas, water and oil pipes to your home’s main earth. If a fault ever made those pipes live, bonding helps stop a dangerous voltage building up and lets the protective devices switch off.
Where you will find it
- Gas: a clamp on the pipe on the house side of the gas meter, normally within 600 mm of the meter.
- Water: a clamp on the incoming metal water pipe, near where it enters the building, after the stopcock.
- Oil and other metal services: where they come into the building.
Each cable runs back to the main earthing terminal near your consumer unit, and each clamp should carry a label: “Safety electrical connection – do not remove”.
Main bonding vs supplementary bonding
Main protective bonding
Connects incoming metal services to the main earth. Most homes need it.
Supplementary bonding
Extra bonding in bathrooms, linking pipes and metal parts. In modern installations it can often be left out when every circuit has 30 mA RCD protection and other conditions are met.
Common problems
- No bonding at all, which is common in older homes.
- Bonding removed when a plumber replaced pipework, or a clamp left loose.
- Cable that is too small for today’s rules.
Missing or inadequate main bonding is usually recorded as a fault on an EICR and needs putting right.
Common questions
Is earth bonding a legal requirement?
Wiring Regulations (BS 7671) require main protective bonding to incoming metal services. Electricians install it to that standard, and an EICR checks it.
What size is earth bonding cable?
In most homes main bonding is 10 mm² green-and-yellow cable, but the right size depends on the supply. An electrician will confirm it.
My water pipe is plastic. Do I still need bonding?
If the incoming water pipe is plastic all the way into the building, water bonding may not be needed. An electrician should check, because a metal section can still need bonding.
Can I fit earth bonding myself?
It needs testing to prove it works, so use a registered electrician. They will check the connection to the main earth and record it.
Not sure your bonding is right?
We check, install and test earth bonding as part of electrical inspections and repairs. See our EICR in Bristol and electrical installations.