There are a few reasons why a radiator leaks water. The first thing to do is to identify the source of the leak and then take steps to fix it.

The following tips should help identify the cause of the leak and the best way to go about repairing it quickly as a water leak can damage the rest of your property, stain your carpets and damage your electrical system.

You will need to prepare for the worst case should water start to pour out of your radiator when you start repairing it so you will need to put a lot of absorbent cloth on the floor around the radiator and use a large bucket to catch as much water in as you can.

How to find the source of a Radiator Leak
Completely drying the radiator with a towel will give you a chance to find the water leak - it is very hard to find the source of a water leak on a radiator when it is wet.

Leaking Radiator Valves
This is one of the easiest radiator leaks to remedy. A leaking radiator valve occurs when the spindle packing within the valve wears out or is damaged. Usually, these leaks occur when the valve is in a 'mid-open' position, so the leak will usually stop when the valve is fully closed.

Note: Thermostatic valves require the thermostatic head to be removed and a cap screwing on to give 100% shut off as most valves pass a certain amount of water to give frost protection to the radiator system.

If you need to replace the valve you must drain all the water from the central heating system and ideally purchase a replacement valve of the same type as your existing valve. Unscrew the nuts connecting the water pipe to the valve and then unscrew the valve to replace it. You will then need to refill the system with water and bleed the radiators to remove air.

Leaking Radiator Valve Spindles
Remove the valve cover and tighten the gland nut within the spindle. If this does not work, you might have to replace the complete valve after draining the system or call in a plumber.

Leaking Radiator Valve/Pipe Coupling
A leak at the radiator valve coupling nut can often be fixed by simply retightening the coupling. If this does not work, you will need to replace the olive inside the coupling.

You must drain the central heating system of water and then loosen the nut between the leaking water pipe and the radiator. Take the olive off the pipe after removing the nut and fitting, replace the olive and reconnect the nut and fitting.
If this does not work then replace the hole radiator valve.

Radiator Leaks Caused by Corrosion
Unfortunately, if your radiator is corroding from the inside out you will likely need to replace the radiator. Add an inhibitor to the water after you have fitted the new radiator to ensure the problem does not repeat itself.