Why is my consumer unit earth cable corroded green and breaking apart?

Finding a green, flaky or crumbling cable inside your consumer unit is alarming, and rightly so. That green colour is verdigris, which is the result of copper corroding when it is exposed to moisture over a long period. The earth cable is one of the most important conductors in your home, and if it has deteriorated to the point of breaking apart, your electrical installation may not be able to protect you in a fault situation. What the earth cable does and why it matters The earth conductor connects metal parts of your electrical system back to the main earthing terminal. If a live wire ever touches something metal it should not, like the casing of an appliance, the earth path carries that fault current away safely and causes a fuse or circuit breaker to trip. Without a reliable earth, that fault current has nowhere safe to go, and the risk of electric shock or fire increases significantly. How corrosion happens Copper corrodes green when it reacts with moisture and oxygen over time. Inside a consumer unit this usually happens because of one or more of the following reasons. 1. The consumer unit is positioned on a damp or cold external wall where condensation forms regularly. 2. There is a slow water leak nearby, perhaps from a pipe buried in the wall or a roof void above. 3. The consumer unit enclosure has gaps or poor sealing that allow humid air in. 4. The installation is old and has simply been exposed to ambient moisture over many decades. What you should do right now Do not touch, bend or pull at the corroded cable. Corroded copper becomes brittle and fragile, and disturbing it could cause it to snap or could create an unsafe loose connection. Do not attempt to clean it yourself or wrap it in tape as a temporary fix. If the corrosion is severe and you can see the cable breaking apart, treat this as a safety emergency. Switch off the main switch on your consumer unit if you can do so safely and without touching any wiring. Then call a registered electrician straight away. If the corrosion looks minor and the cable still appears intact, you still need an electrician to inspect it, but it may not require an emergency callout. An electrician will carry out proper tests to confirm whether the earth path is still reliable. Always use an electrician registered with a competent person scheme such as NICEIC, NAPIT or SELECT in Scotland. Ask them to carry out an Electrical Installation Condition Report if one has not been done recently, as corroded earthing is rarely an isolated problem in older installations.