All central heating systems that are pressurised systems will need to be repressurised at some point so that they continue to work as efficiently as possible. This generally requires manually topping up the amount of water within the system and although this sounds like a daunting task, anyone can do it as long as they have a good set of instructions and the handbook to their boiler.

Why does this have to be done?
Everyone knows that heating water over and over makes some of it evaporate and this is exactly what happens in your central heating system. Every time you turn your boiler on and heat the water in the system, a small amount of it evaporates and eventually the water pressure begins to fall. If left, the pressure can fall so far that your boiler will stop working and so you need to repressurise the system as soon as you notice a fall. There are other reasons for a fall in pressure, such as leaks in the system, but these will require the help of a professional and shouldn’t be tackled alone.

How do you know your system needs repressurising?
All boilers that are part of a pressurised system will have a very obvious and easy to read pressure gauge which monitors the water pressure within the heating system. This gauge needs to be checked on a monthly basis to see that the pressure is within the recommended levels – these will be noted in the boiler’s handbook. If the pressure has dropped then it’s time to repressurise.

How do you repressurise a boiler system?
Firstly you need to locate your filling loop. This will be located close to the boiler and looks like a stop tap with one end attached to the cold water mains pipe and the other end attached to the central heating system pipe work. Occasionally, the filling loop may not be permanently attached to the heating system and so you will need to attach it first before turning the tap! In some cases the filling loop may be integrated within the boiler itself and you will need the boiler handbook for further instructions.

Once the filling loop is attached to the system you can open the tap but it is best to do this slowly as you don’t want to flood the system. When the tap is opened, cold water is injected into the central heating system and the pressure gauge on the boiler should begin to rise. Make sure you or someone else can see the gauge as you don’t want to over pressurise. If you do slightly over pressurise the system the safety valve will kick in an release the excess pressure but this only works to a certain degree so keep a close eye on the gauge.

When this is done you simply disconnect from the system if need be and check the gauge over the next couple of days to see there are no problems. Most systems only need repressurising every three or four months and then it isn’t by much however it might be worth checking a bit more frequently over the winter months when the boiler is on much more often.

Guest Article by Clare Lynock