What to do if your boiler loses pressure

Stay calm under pressure with our handy guide to the most common boiler pressure problems and how to fix them.

What is boiler water pressure?

Boiler problems are the last thing you want. Especially when it stops you from getting any hot water. When this happens, it is often because boiler pressure is too high (or low) but thankfully it’s relatively easy to diagnose and fix, in some cases.

Your boiler heats cold water that flows around a circuit of pipes and radiators through your home. For it to work as efficiently as possible, your water pressure needs to be stable. Pressure in most combination boilers is maintained by a ‘filling loop’, which connects to your cold water pipe. More on this later!

How can I check my boiler pressure?

On the front of your boiler, you should find a water pressure gauge. If you’ve got a hydraulic pressure gauge, you’ll see low and high pressure indicated by red sections on the dial. The position set when the boiler was installed is sometimes shown by a red indicator needle. On most digital gauges, you’ll see a flashing pressure reading if the boiler pressure is too high or low.

If your boiler pressure reads less than 1 bar, you might have lost water from the system. This will need to be replaced and is where that filling loop comes in again.

If the pressure gauge is above 2.75 bar then that’s a sign of a high pressure boiler. You’ll need to bleed a radiator to bring the level down to 1.5 bar. More on this…right now.

What to do if your boiler pressure is too high

This is a hot topic, quite literally, so let’s look into making sure your boiler pressure isn’t too high when your heating’s on. First of all, you need to identify why you have a high-pressure boiler. The common culprits:

Pressure valves

Check underneath your boiler. Make sure the valves are closed tightly as they may have come loose accidentally and caused your boiler pressure to become too high.


Bleeding your radiators can help to reduce the pressure load and it’s fairly easy to do. However, if you have noticed the boiler pressure is too high when the heating’s on, it does mean you need to be careful of the hot water inside the system. If you’re unsure, we recommend you get an engineer to take a look as it could always be a fault inside the boiler. Plus, our engineers are amazing at bleeding radiators, minimizing spills and making sure nobody gets scalded by excess hot water!

How to reduce boiler pressure

To get your boiler back fighting fit, you’ll need to know how to reduce boiler pressure. Obviously, each boiler has a different system so it’s always good to check your manual, if you still have it. You should be able to find these online and some boilers have instructions on the rear of the control panel. If you decide this isn’t a job for you, then maybe it’s one for us – get in touch and let us help. Otherwise, try these basic steps:

  • Switch off your boiler and allow it to cool
  • Double check that both ends of the filling loop are securely attached
  • Open both valves to allow cold mains water into the system. Listen out, you should hear it
  • Wait for the pressure gauge to read 1.5 bar
  • Close both valves, one after the other
  • Switch the boiler back on. If needed, press the reset button
  • Undo both ends of the filling loop and remove. Be careful to catch any water spillage and keep the filling loop in a safe place

Want an expert to help?

If you’re unsure on how to release pressure from your boiler or you’ve tried it and it’s still not working, we’re here to help. Our expert engineers will diagnose and fix the problem for you.

If you’re already a HomeCare customer, we’ve got you covered. Book an engineer anytime from your online account.

And if you aren’t a British Gas customer, you can always book a one-off repair at a competitive fixed price.

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