Under Pressure: Everything You Need to Know About Boiler Pressure

If you have a boiler in your home, it is likely that at some point you have experienced boiler pressure issues. It is important to maintain the correct pressure to ensure that your boiler system works correctly.

What is the Correct Pressure for a Boiler?

Ideally, your boiler’s pressure should be sitting somewhere between 1 and 1.5 when your heating is not in use. When the heating is on, you may see a rise to between 1 and 2 bars.

Anything below 1 will begin to impact your heating and hot water. Oppositely, if you notice a pressure of 2.5 or over, there is a huge risk of damage to your boiler.

Has Your Boiler Lost Pressure?

Here are some key characteristics of your boiler pressure being too low to look out for:

• You don’t have any hot water or heating
• Your radiators are struggling to warm up
• The dial on your boiler has fallen

This could be due to a leak in your radiators or even after bleeding them. Your boiler pressure being too low isn’t dangerous, but it is always best practice to raise the pressure when you notice it’s low.

How to Raise the Pressure

You can increase your boiler pressure yourself, this is known as ‘re-pressuring your boiler.’

1. Always start by turning off your boiler.
2. Look for an external filling loop which you can usually find under your boiler. This will look like a short length of braided hose that links two water pipes together. At the end of this, you should see levers that work valves.
3. If you don’t have a filling loop on your boiler, you may have a model that requires a keyed filling loop or a keyless internal filling loop. Check your instruction manual if unsure.
4. Turn both of the valves so that the levers are aligned with the direction of the braided hose. You will hear water running and the pressure gauge increasing.
5. Once you reach 1.2 bar, turn off both valves.
6. Hopefully, the pressure stays up, with no signs of obvious leaking water. From here it is safe to turn your boiler back on.
7. Once you have run the boiler and it’s cooled down, check the pressure again to see if it hasn’t dropped.

You won’t need to increase your boiler pressure very often, but if it drops more than twice a year, there may be a bigger overall problem. Check all visible pipes for water leaks and look out for green deposits near the joins in copper piping.

Has Your Boiler Increased in Pressure?

Look out for the following signs of pressure increase:

• The pressure dial is sitting within the red zone of the pressure gauge.
• The system has completely shut down.

Your boiler might be rising over 3 bars due to:

• Accidentally putting too much water in when attempting to increase low pressure.
• You may have left the filling valves open or not screwed them closed tight.

How to Reduce the Pressure

Again, this can be done yourself. Always refer to your boiler’s instruction manual.

1. Shut the boiler off.
2. Check that the filling loop valves or the key or keyless filler are closed fully.
3. Allow the system to cool down, then release some pressure by bleeding each of your radiators. Learn how to do this by clicking here.
4. Once the bleeding is done, check your boiler’s pressure gauge. If it’s still too high, you will need to bleed a few more of your radiators.
5. Keep checking your boiler, you want it to read 1.2 bar or at the very least the dial needs to be back in the green.
6. If your pressure becomes too low, repeat the steps from How to Raise Boiler Pressure above.

Looking to Upgrade your Boiler?

Dealing with your boiler pressure may be growing tiresome. If this is the case, you may want to consider upgrading your boiler to a modern energy-efficient model like an air source heat pump. You may even get some help towards one with the Boiler Upgrade Scheme (BUS).

Use the button below to check your eligibility for the government-backed Boiler Upgrade Scheme!