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It’s hardly ideal on cold winter days when your radiators heat up slowly, or develop cold spots. It happens because the hot water flowing into them from your boiler isn’t being distributed evenly.

Balancing your radiators is just a matter of allowing more water to flow to the colder radiators. If some of your radiators also have cold spots, they probably need bleeding too.

Yes, it involves using a few tools and turning the heating off and on, but it’ll be well worth doing if you want to stay warm.

What you’ll need: A radiator bleed key. A lockshield valve key or adjustable spanner. A screwdriver. A digital thermometer/multimeter with thermometer.

Next, get to know your radiator valves.

A manual valve. This is the old-fashioned type that you can use to turn your radiator on and off. It’s also called a wheelhead or control valve. It only has two positions – on or off – so that’s the only control you have over the amount of hot water flowing into your radiator.

A thermostatic Valve (TRV). Most modern radiators have one of these rather than the manual kind. It looks like a dial with numbers on it and has its own thermostat. Once the surrounding temperature reaches your desired level, the valve regulates the hot water flow into the radiator.

A lockshield valve. This will be covered by a small domed plastic cap. You’ll need to use grips of some kind to pull off the plastic cap. Some have a screw through the top of the cap that needs removing to get the plastic cap off. Underneath the cap is what looks like the end of a flat-head screwdriver.

How to bleed radiators that have cold spots.

  • First turn off your central heating and wait for your radiators to cool down.
  • List all the radiators in your home on a piece of paper. (You’ll need this later once you’ve opened all the valves.)
  • Now open BOTH radiator valves on each of your radiators completely by turning them anti-clockwise (to the left). For manual valves and TRVs it’s easy to do by hand. For Lockshield valves, remove the plastic cap (instructions above) and turn the metal valve anti-clockwise with a Lockshield valve adjuster or an adjustable spanner.
  • Identify the fastest heating radiator.
  • Turn the heating back on and walk around your house with your radiator list to find the radiator that heats up first. (Probably the one closest to your boiler.)
    You’ll probably need a bit of help from your partner or kids to do this.
    Give each radiator on your list a number in order of how fast they started to heat up.
  • Turn the heating off, check all your radiators have cooled down completely and then switch your central heating back on again.
  • Using your list, go to the fastest heating radiator in the house and turn the Lockshield valve clockwise until it’s completely closed, then open it by a quarter of a turn.
  • When the radiator has heated up, take a temperature reading at the pipework connected to the Lockshield valve, where it meets the floor or wall.
  • Now take the temperature of the pipework leading to the manual valve/TRV. Slowly open the Lockshield valve until the temperature reading is around a 12-degree Celsius difference from the Lockshield valve reading you took. (This will need to be in accordance with the manufacturer’s instructions.)
  • Do this for the rest of your radiators and balance will be restored.