Radiator Problems

Radiator problems

When a radiator isn’t working correctly it can turn a room into an ice box in a British winter. Here we look at some of the common problems.

Radiator is cold at the top, but warm at the bottom – The most common reason for this is that there is air in your system and can usually be solved by bleeding the radiator. This can happen after long periods of the heating not being used. You’ll need to buy a radiator key, if you don’t already have one, which can be purchased from most home improvement stores.

You’ll need to turn the key just enough so you start to hear air hiss out. Be ready to turn it back as once the water reaches the top of the radiator the hissing air will be replaced by water. Hold a rag below the bleed valve while you work, to catch any water which gets out before you close the valve again. Remember that the water will be hot!

Note: Bleeding the air out of your system will cause the overall pressure to drop. Check the pressure gauge on your boiler – if the needle is below the green area, then top up the water using the filling loop (instructions for this should be with your boiler)

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One radiator is cold all over – This might simply be because the radiator has been turned off using the valves. The larger one (usually to control the temperature) and the smaller one (an isolation valve).

The smaller valve doesn’t normally need adjusting – that’s set to allow a certain flow of water into that radiator to keep the flow balanced across all the radiators in your house. So try the larger valve first, which you should be able to turn by hand. Turn it anti-clockwise to open up the valve. Wait a few minutes to see if the radiator now gets hot.

If it doesn’t, you can try opening (turning anti-clockwise) the other valve, but bear in mind that you might then find another radiator stops working as too much water is coming in to the radiator you’ve adjusted, leaving another one short of hot water flow. In that situation, you’ll need to balance all the radiators: turn off the valves on every radiator apart from the cold one. The cold one should then warm up. Slowly work your way around every radiator in turn, opening up each valve a tiny bit (an eighth of a turn), and repeat this until every radiator is warm and at roughly the same temperature.

Thermostatic valves and cold radiators – These valves are used to control the temperature of a specific radiator with a valve opening and closing automatically. If the valve head has failed, you can replace it easily enough (it’ll just unscrew off the top of the valve, leaving the valve itself intact). But if the actual valve has failed, you need to drain down the whole system to replace it.

All radiators are cold – the first thing to do is check that your boiler is working and that the gas burner is lit. If it’s a combi boiler you should also check that the pressure is in the correct range shown in your user manual.

Radiator is warm at the top, but cold at the bottom – This is unusual and usually means that you have sludge in your system and you need to have the system flushed out by a heating professional.


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