How To Re-Pressurise Your Boiler

If one day your central heating suddenly cuts out, loss of water pressure in your boiler may be to blame. Each boiler has a water pressure indicator and should give you a common reading between one and two bars. If this isn’t the case and your indicator shows below one bar, your water pressure is too low. Don’t deem yourself doomed too soon! There’s always a silver lining and in this case, it is relatively easy to diagnose this problem and put it right yourself.

how to repressurize boiler

What is Boiler Pressure?

In a nutshell, your boiler heats cold water in the tank which flows through a series of radiators and pipes throughout your home. Your water pressure needs to be in-check in order for the water to flow through your home efficiently. Visit Radiator Outlet to buy a new radiator. In most modern boilers, the pressure is controlled and maintained by a ‘filling loop’, which connects to your cold water pipe. We’ll look further into this.

Why is my Boiler Pressure Low?

Two of the commonly known reasons why your boiler pressure is low are either because there is a water leak somewhere in the system or reduced system pressure as a result of bleeding a radiator.


It very well may be that you have a leak somewhere in your boiler system. Sometimes leaks can be so minuscule that they tend to go unnoticed, but if this is the case, there could potentially be a gradual drop in pressure.

It is not always easy to come across a water leak in your system due to pipework that is not visible. The places to look for leaks in your system are around your house for signs of damp patches, around visible pipes, radiators, and the boiler itself. Although, do not go and look for leaks inside the boiler, make sure that only a Gas Safe registered engineer opens your boiler. Remember, you’re better safe than sorry!

Bleeding Radiators

If you have been trying to improve the performance of your system or deal with radiators that are not heating properly, you may well have recently bled a radiator. When you bleed your radiator, it allows air that has been collected within a system to escape, resulting in a drop in pressure.

Can I Fix Low Boiler Pressure Myself?

Always be cautious when attempting to fix low boiler pressure yourself. It is always recommended to check your manual whether or not you are able to re-pressurise it yourself.

It is is also worth checking your boiler brand’s website for any informational guides or videos to assist you in the process.

By re-pressurising your boiler, you are essentially allowing more water to enter the system, from the water mains supply, via the filling loop. Follow our step by step tutorial on how to re-pressurise your boiler:

  1. Identify your filling-loop and pressure gauge. The filling loop handles should be at a 90° angle to the flow of the pipe
  2. Make sure the pressure gauge is in sight while accessing the filling loop. For modern heating systems, the pressure level will be shown in green on the gauge, but it is always double-checking in the manual for your specific boiler. It may be beneficial to seek help if you are unsure
  3. Turn the boiler off
  4. Turn both of the filling loop handles towards the direction of the pipe. Once done, you should be able to hear the flow of water.
  5. Once the correct pressure is reached, make sure the handles are fully closed by returning them to the 90° position.
  6. Turn the boiler back on and check to see if the boiler remains steady between one and two bars

If these steps have helped you fix your low boiler pressure, you can sit back and relax!

If this becomes a recurring problem, this is a sign that something is wrong and it is advised to contact a gas safe engineer.

Recommended Reading: How to Find the Right Boiler

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