How to Fix a Radiator Not Heating Up

A cold radiator is one of the most common home maintenance issues in the UK, and in most cases it is something you can fix yourself in minutes.

Likely causes

• Trapped air in the radiator (cold at the top)
• Sludge build-up in the radiator (cold at the bottom)
• Thermostatic valve not open
• Radiator valves turned off
• Boiler pressure too low

Step-by-step fix

1. 1
   Bleed the radiator if cold at the top

   Turn the heating on and feel the radiator. Cold at the top but warm at the bottom = trapped air. Turn heating OFF. Use a radiator key to open the bleed valve (small square at the top corner). Hold a cloth underneath. When water (not air) comes out, close the valve.

2. 2
   Check the thermostatic valve

   The TRV (thermostatic radiator valve) is the plastic-headed valve on one side. Make sure it is turned up (not set to 0 or * position).

3. 3
   Check the lockshield valve

   The lockshield is the valve on the other side with a plastic cap. It should be open — turn it anti-clockwise to open.

4. 4
   Power-flush if cold at the bottom

   Cold patches at the bottom of a warm radiator indicate sludge. Try adding central heating inhibitor/cleaner (available from B&Q) to the system, or call a plumber for a power flush.

5. 5
   Check boiler pressure

   Most combi boilers should be at 1-1.5 bar when cold. If the pressure gauge shows below 1 bar, repressurise the system using the filling loop beneath the boiler.

6. 6
   Bleed all radiators after repressurising

   After adding pressure, bleed each radiator starting from the ground floor.

Frequently asked questions

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