Why radiators need bleeding?

All radiators require bleeding to remove air bubbles that form periodically during the life of a system. Air can be introduced into a central heating system in several ways.  It can occur when new water enters the system from the expansion tank or when a routine maintenance is carried out.  It could also be ‘created’ by the movement of the central heating system pump as it turns.  When radiators are not working properly, or when they are not putting out as much heat as they should, some parts of the house will be colder than others. When the house still has cold rooms, people tend to turn the thermostat higher than normally required, adding considerably to their central heating bill.

How can you tell if your radiator needs bleeding?

Signs that your radiator needs bleeding are, if your radiators are taking a long time to heat up and

when the top of a radiator is cooler than the bottom. In severe cases the entire radiator can be cold when the heating system is on. So to check if your radiators need bleeding.

  • Put your central heating fully on.
  • Wait for your radiators to reach their maximum heat.
  • Feel along the top of each radiator for any cold areas, being careful not to burn your hands.
  • If you feel any cold areas, this indicates trapped air and the radiator needs to be bled.

It is recommended that radiators are checked every two to three months.


How to bleed a radiator?

If you decide not to contact your heating engineer to bleed your radiators, here are some useful tips.

1. Turn off the heat

This is very important, boiling water could result in injury and a ruined floor. Also some central heating systems have water pumps that, depending on where in the system they are fitted, will actually suck more air into the radiator, if the central heating system is left on when you open the bleed valve.

2. Bleed radiators in the correct order.

In homes with more than one floor, the lowest floor radiators should be bled first, beginning with the radiator receiving the water flow last i.e. furthest from the boiler. The radiators on each floor above should then be done in turn, again beginning with the radiator furthest from the boiler.

3. Use a radiator key.

You risk damaging radiator valves by using pliers and although a screwdriver can be used to bleed some modern radiators, most radiators require a radiator key. These keys are available in most DIY stores.

4. Always have cloths and towels to protect yourself and prevent damage.

It is advisable to wear tight fitting rubber gloves and holding the key with a cloth, slowly turn the radiator valve anti-clockwise to open your radiator’s valve until you hear a hissing sound of air escaping. Make sure you have a towel or cloth below to catch any water. Be careful not to open the valve too much, if you release the centre pin it could lead to an excessive amount of water loss and damage.

Once the air has all escaped and water starts to leak out, tighten the valve by turning the key clockwise. Be careful not do this too tightly, as you could damage the valve. With many of the modern screwdriver operated valves water escapes as a jet, rather than a dribble.

5. After bleeding radiators always check the boiler pressure.

Once all your radiators have been bled, check the pressure on your boiler gauge. If the pressure is normal you can switch on your heating and check that there are still no cold areas. If your pressure is too low, you should rebalance the pressure.

The advantage of using a qualified Curve Heating engineer to service your boiler is that we can check and bleed all your radiators within the same visit and price.

Please Note:

With modern central heating systems, there is minimal danger, as long as your boiler is regularly serviced. However, the reason Landlords are required by law to provide annual boiler servicing, is that without annual servicing, your boiler can become dangerous.

Safeguard your home and family and have your boiler serviced every year, by one of Curve Heatings qualified engineers.

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