Why is my radiator cold at the top?

Bleeding Radiators

This one of the most common issues experienced when it comes to central heating systems.  Radiators are designed to be full of hot water which is pumped around by the boiler system.  If the radiator is anything but completely full of water, it will affect the output and performance of the radiator.  A radiator will feel cool at the top and warmer at the bottom if it needs bleeding of air.  This is actually very simple to do using nothing but a simple bleed key.  

What you need:

A bleed key

A rag to catch escaping water from the bleed vent.


How to bleed a radiator:

Find the bleed vent on your radiator.  This is located at one of the top corners of the radiator.

Place the key on the bleed vent and turn anti clockwise to loosen.  As you do this you will initially hear a rush of air being vented out of the radiator.

Place your rag to catch escaping water when the air has been purged.

Once you see a steady stream of water escaping, tighten the bleed vent using the bleed key.


You should now feel the top of the radiator getting warm- give yourself a pat on the back!

Radiator Bleed key Venting