Easy Fixes for a Cold Radiator

Problems with heating often come to light in the autumn when you turn on your system after a summer break. Many problems with finicky radiators can be addressed in minutes with minimal effort.

Easy Fixes for a Cold Radiator

My radiators are stone cold

Check your central heating boiler and pump

If all of your radiators are cold:

  • First, check that the heating programmer and thermostat are set correctly. Make sure that both Hot Water and Central Heating are enabled on the programmer — you can usually override its timer to activate both instantly; the button that does this is often labeled "Continuous." Set the thermostat to a higher temperature.
  • Confirm that the boiler is working. Does it feel warm? Most boilers have a dial that allows you to control the temperature of the water as it leaves the boiler for the hot-water tank and heating system. Make sure this is turned up. If the boiler won't fire up, call a technician.
  • The problem may lie in the electric pump that circulates hot water through the radiators; this can get clogged with particles, especially if inactive over the summer. Can you hear it working or feel it vibrating? If not, remove the screw on the face of the pump with a large flat-head screwdriver. Beneath, there is a smaller slot that connects directly to the pump's movement; insert a screwdriver into the slot and turn it gently each way — this is often enough to get the pump moving.

The top of the radiator is cold

Bleed air from the radiator

A radiator that is hot at the bottom and cold at the top needs bleeding to remove any trapped air. You'll need a bleed key, which can be bought from any hardware store (though some valves can be opened with a screwdriver).

  • Switch the heating off at the control panel and locate the radiator's bleed valve; it is usually at one end of the top of the radiator.
  • Insert the key and turn the valve counterclockwise until you hear air hissing out; as the air is released, the radiator fills with water.
  • Be ready with an old cloth to soak up any water that spurts out of the valve once the radiator is full. Close the valve the moment this happens; don't overtighten it, or you'll have trouble opening it next time you need to bleed the radiator.
  • If your radiator is cool at the bottom and hot at the top, it is probably clogged up with sludge. It will need to be removed and flushed clean — a job for a plumber.
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