6 Things to do if your Boiler Pressure is too Low

If you’ve got a modern boiler, you’ll find that it’s economical to run and you’ll save money on your energy bills compared to a boiler that’s over 10 years old. But from time to time, it might need a bit of care and attention to keep running smoothly.

One of the most common problems in boilers is low pressure, but thankfully it’s usually a simple fix that won’t require a Gas Safe engineer to come out. Read on to find out how to find out if your boiler pressure is low, what to do to solve it, and when to seek help from an engineer.

How to find out if your boiler pressure is too low

1.      Check your pressure gauge

pressure gauge on a boiler showing green level

Most UK households now use a gas combi boiler for heating and hot water. There should be a circular pressure gauge on the front of your boiler, and it may have green and red zones on it.

The green zone is usually between 1-1.5 bar, and is the standard operating pressure. The red zone is the maximum safe operating pressure. If the needle of your pressure gauge has fallen below the green zone, it means your boiler pressure is too low and you should investigate the problem.

2.      Check your radiators are heating up properly

Turn your heating on and see how your radiators heat up. If they don’t heat up as quickly or like they should do, it could be a sign that your boiler pressure’s low. Then take a look at your boiler’s pressure gauge, which should confirm if there’s a problem.

What causes a boiler to lose its pressure?

There are a couple of common reasons why your gas boiler pressure might be too low: either a water leak or a recently bled radiator.

Finding a water leak

It can be difficult to find water leaks, as lots of your pipes in your central heating system will be covered. But if you are experiencing low boiler pressure, it’s worth taking a look at all the pipes you can see.

Check for any water on the pipework or any damp patches or stains. You might also notice swelling in skirting boards. If you’ve got copper pipes, water will cause them to turn green, so that’s a sure sign that you’ve got a leak.

Common places to spot leaks are joints in the pipework and the points where pipes connect to the radiators.

Bleeding radiators

Most people know that if your radiators aren’t heating up fully, it may need bleeding. This lets air that has collected in your central heating system to escape and will allow the radiator to heat up across its entire surface again.

However, if you’ve just bled a radiator, this could cause your boiler pressure to drop. In that case, you should look at our steps on how to fix the low pressure in your boiler.

How to fix your boiler’s low pressure

Luckily, if your boiler pressure is too low, it’s pretty easy to fix. You just need to re-pressurise the system. You can do this by yourself, if you feel confident enough – but make sure you check the user manual of your boiler to check that your model allows you to do so.

Just follow these 6 simple steps:

1.      Find your filling loop

Your filling loop should look something like this:

loop of pipe connected to the boiler

Make sure the handles are at a 90-degree angle to the flow of the pipe.

2.      Make sure you can see your pressure gauge

Make sure you can see your pressure gauge at the same time as your filling loop. Later on, you’ll need to be able to check that the pressure is at the correct level, whether that is by looking for the green area on the gauge or by checking your boiler’s manual.

3.      Turn off your boiler


4.      Turn the filling loop handles

You’ll need to turn your filling loop handles at a right angle so they match the direction of the pipe. If you’ve done it correctly, you’ll hear water flowing.

5.      Watch the pressure gauge

Watch for what the pressure gauge does and when it reaches the right pressure, make sure the handles are closed by putting them back to the 90-degree position.

6.      Turn the boiler on and check

Turn your boiler back on and check to see if the pressure remains steady. If it does, you should have fixed the problem!

When to call an engineer

If your boiler pressure drops again, it could be a sign that something else is going on with your boiler. It’s best to get a Gas Safe registered engineer to come out and take a look at your boiler – you should never try to carry out complex gas work yourself, as this could be dangerous and will also invalidate any warranty you have.

Use our simple form below to get in touch with up to 4 boiler engineers who will be able to help if your boiler pressure is too low. It’s free and you’re under no obligation.

Emily Rivers

Emily Rivers is the Customer Experience Manager at Quotatis. She informs customers of the latest developments in a range of products so they can make the best choice for their homes and ensures they get the best out of our service.

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