How to Fix a Cold Radiator
Fixing a Cold Radiator
If one of your radiators feels cooler at the top than at the bottom, it’s likely that a pocket of air has formed in it and is impeding the circulation of the water. Trapped air stops radiators heating up fully, and regular intake of air can cause corrosion. Getting the air out — ‘bleeding the radiator’ — is a simple matter.
- Radiator key
Releasing the air
First switch off the circulation pump — and preferably turn off the boiler too, although that is not vital.
Each radiator has a bleed valve at one of its top corners, identifiable by a square-section shank in the centre of the round blanking plug. You should have been given a key to fit these shanks by the installer; but if not, or if you have inherited an old system, you can buy a key for bleeding radiators at any DIY shop or ironmonger’s.
Use the key to turn the shank of the valve anticlockwise about a quarter of a turn. It shouldn’t be necessary to turn it further — but have a small container handy to catch spurting water, in case you open the valve too far, plus some rags to mop up water dribbling from the valve. Don’t be tempted to speed up the process by opening the valve further than necessary to let the air out — that is likely to produce a deluge of water.
Clearing a blocked valve
If no water or air comes out when you attempt to bleed a radiator, check whether the feed-and-expansion tank in theis empty. If the tank is full of water, then the bleed valve is probably blocked with paint.
Close the inlet and outlet valves, at each end of the radiator, then remove thefrom the centre of the bleed valve. Clear the hole with a piece of wire and reopen one of the slightly to eject some water from the hole. Close the radiator valve again and refit the in the bleed valve. Open both radiator valves and test the bleed valve again.
Dispersing the air pocket in a radiator
You will hear a hissing sound as the air escapes. Keep the key on the shank of the valve — then when the hissing stops and the first dribble of water appears, close the valve tightly.