How to Repressurize Your Central Heating System

What You'll Need
Radiator key
Bucket or jar

Finding that your central heating system isn't working properly can mean that you might need to repressurize the system. Following a few steps to undertake the task will help to rectify the problem and ensure the system works as it should.

Step 1 – Assess System

You must first need to know whether your central heating system requires the work necessary to repressurize it. Undertake an inspection of the system by turning it on and checking whether the heat is evenly distributed. Where certain sections of the radiators remain cool, you can accept this as an indication air in the system and that the pressure needs to be adjusting. You should also take note of any unusual noises that are produced by the radiators, pipes and/or boiler while the central heating system is in operation.

If there is a change to the length of time it takes for the system to come on, this may also be an indication of a failure to the pressure. Check the pressure gauge attached to the boiler, it should be at a reading between 0.8 and 1.5 and anything outside this will confirm that you need to adjust the pressure.   

Step 2 – Repair

A central heating system can lose pressure due to a boiler that is suffering a leak. Even a small leak that would otherwise not be noticed can result in a significant loss of pressure as it gives water access to enter. Examine the boiler to check for any sign of leaks, which may only be marks left after water has evaporated. Use a wrench to tighten any nuts that require it.      

Step 3 – Bleed Radiators

Once the repair has been completed, you can undertake the work necessary to remove the air from the system. After making sure the central heating system is turned off, slot a radiator key into the corresponding hole at the side of the radiator. Hold an empty container beneath the nozzle to catch any liquid and turn the key to release the air until a trickle of water flows from the nozzle. Take care with this step as the water may be hot. After a small amount of water has been discharged, turn the key back the other way to close the cavity. You will then be in a position to switch on the heating system to check whether the heat is evenly distributed.       

Step 4 – Fill Boiler

In the event that the pressure gauge attached to your boiler is displaying a number that is not sufficient to maintain the pressure, work needs to be undertaken to the boiler to rectify this. If you have retained the instruction manual, use this to help you find the location of the filling loop. This component is likely to be close to the boiler and look like the head of an outdoor faucet. Turning this will enable water to flow into the system which you will probably be able to hear. Keep an eye on the pressure gauge so that you are aware when it the pressure is at an optimum level. Check the pressure gauge on a regular basis.