How to bleed a radiator

25 November 2019

a photo of someone adjusting the valve on a white radiator

If things start getting a little chilly in your home and you’re wondering why, look first to your radiators. It can be the case that, even with the central heating turned up high, they are failing to deliver the warmth you would expect.

If your radiators are cool at the top but warm at the bottom, it’s probably because they have air in them and need bleeding.

Bleeding radiators may sound like a messy and complicated affair, but not to worry – it’s actually far simpler than it sounds. As long as you’re ready with the right tools (a simple valve key and a cloth) it shouldn’t take more than a minute for each one. Follow these easy steps and your home will soon be warm and cosy again. If you don’t have a  radiator valve key, these can be purchased at any DIY store.

  1. Keep your heating system on low so it remains pressurised, but be aware that the water in your radiators will be hot, so do take extra care.
  2. Attach a radiator key to the bleed valve, usually located at the top and to one end of the radiator, and slowly begin to turn anti-clockwise.
  3. Keep turning until you hear a slight hiss of air. When water begins to escape instead of air, you know it’s time to close the valve as all of the trapped air has now escaped. Hot water may spurt out quite quickly so do protect yourself and the area around.
  4. Tighten up the valve by turning the key clockwise.
  5. If you have a sealed central heating system you may need to re-pressurise the system. An explanation of how to do this is given in our  How to re-pressurise a sealed central heating system.
  6. Enjoy the results!

Throughout this process you should always place a cloth beneath the valve to catch any water that might leak from it, which could discolour floor coverings due to the additives within the heating system.

Every new-build home in the UK that is sold with an NHBC Buildmark warranty and insurance policy comes with a secure, online Home User Guide (HUG). HUG is a free, personalised portal where you can store all the information you need about your home. It also contains useful advice about moving into a new home, designed to help you settle in as smoothly as possible.

This how-to guide and the accompanying video is just part of the guidance available on HUG. If you’re in the process of buying a new-build home, or have recently bought one, with Buildmark cover make sure you check out HUG. It’s also the place where you can most conveniently accept your Buildmark cover.

Remember, most repair and maintenance ought to be carried out by a professional.

Take a look at our other how-to guides:

How to attach pictures, shelves and curtain poles

How to attach a floor fixing

Decorate your new-build home

How to connect a kitchen appliance

How to re-pressurise a sealed central heating system