How To Bleed a Radiator

How air can integrate itself in a water central heating system

When water is newly added to a central heating system, a certain degree of air will also find its way inside. Due to the fact air will rise in these systems, it will collect at the highest points in the system, especially if it is part of a long collection of pipework.

Checking the System for Air

This is exactly why trapped air in radiators can become a problem. The added water in the system along with the large circulation of pipes makes it a prime target for rising air. The result is a large loss of heat in your radiators, hence the problem.

To test if you have this problem, first turn on the central heating. You then need to test the radiators in your house for temperature differences in the top of your radiator and the bottom. If the top is cool and the bottom warm, it is highly likely you have significant air in your system.

If the amount of air in your radiator system is severe, then you will not notice any change in temperate as the entire radiator is likely to be cold or at least cool. The next step is to test the radiator and check that air is the problem rather than any underlying problems.

Testing Your Radiator Via Bleeding

Before we start, please do not forget to turn your central heating system off. If you are unsure of what exactly to do then consult a professional plumber as you could potentially make problems worse.

When you bleed the system, this will cause a drop in the pressure as you release the potential in the system of pipes. If you are unsure of how to re-stabilise the pressure in your system then please do not attempt to do this.

1. Once you have warm water in the radiator, turn off the Central Heating system.
2. Depending on the design of your radiator, locate and the fit a key into one of the turn valves. This is usually at either side of your radiator on the bottom..
3. Place an old cloth around the key to absorb any loose water.
4. Turn the key anticlockwise slowly, you should be greeted by the sound of air hissing from the system.
5. As soon as water begins to slowly run down the side of your valve, turn the key back to close it off. Please ensure you do not over tighten the valve as this can cause problems in the future.
6. If the Central Heating system is a sealed system, check the pressure and, if necessary, top up the pressure as required, this is usually by 1 bar but always check your own instruction manual.