11 April 2019 - 15:52, by , in Boiler Help, No comments

The Ultimate Guide to Boiler Pressure Problems

Having problems with your boiler? Ouch! That’s never nice. But the good news is there’s most likely a reasonable explanation for it, and it should be fairly straightforward to diagnose and fix.

A lot of problems occur when the boiler pressure is either too low or too high.

Here’s our handy Hug guide to common boiler pressure problems, how to diagnose them, and what you need to do to get your boiler back to full fitness.

What is boiler pressure?

Good question! That would be a pretty logical place to start, wouldn’t it?

First thing’s first: let’s not get confused with plain old water pressure.

When we talk about boiler pressure, we’re referring to the water which runs through your enclosed central heating system.

Water pressure refers to your taps and the pressure of the water flow.

So why is boiler pressure important?

Your boiler heats water, which is carried to different parts of your house through a series of pipes and into your radiators. In order for the central heating system to function properly, the water pressure needs to remain stable.

If your boiler pressure drops too low then the system might refuse to do what it’s supposed to.

On the other hand, if the pressure rises above a stable level then your system will find itself under increasing strain, stop working altogether and you’ll finally be able to use those extra thick woolly socks that you get every Christmas.

How do I know what my boiler pressure is?

If you’ve got a gas combi boiler, as most UK households do, you should be able to easily locate the pressure gauge on the control panel of the boiler itself. It’s a little circular thing with green and red arrows. Green means good, red means bad.

The green zone indicates a pressure of between 1 and 2 bar, which means everything should be in good working order. Some older systems might only have a green zone of between 1 and 1.5 bar. Once the needle ticks over into the red zone, that means your boiler is no longer operating safely.

As your central heating system kicks into action, you should be able to see your boiler pressure rise a little bit, and if you find yourself getting really bored you can even watch it drop by around 0.3 bar when you turn the heating off.

Low boiler pressure

How do I know if my boiler pressure is low?

There are a number of things you might notice before you check the pressure gauge and realise that the boiler pressure is too low. Here are a few common low-boiler-pressure symptoms:

There’s a leak

It might be glaringly obvious or hardly noticeable, but even the tiniest of leaks can cause big problems.

Take a look around for any signs of damp or dripping around pipes, radiators and the boiler itself.

NEVER open your boiler up, though. Only a gas safe registered engineer should be gaining access to that inner sanctum.

Boiler noises

The most obvious sign will be an array of strange noises coming from the boiler or the central heating system.

If you start noticing any of these then either your boiler pressure is too low or your house is haunted. Both pretty scary.

You might be able to hear:

  • Banging noises
  • Rumbling noises
  • Vibration
  • A noise like a kettle
  • High pitched noises
  • Whistling noises
  • Grinding noises

Radiators not working

If your boiler pressure drops in the middle of winter, you’ll probably notice this first.

Usually the radiators furthest away from the boiler are the first to cut out, followed by the rest of the upstairs.

You might also notice that some, but not all, heat is getting through despite the thermostats and valves being on full blast.

Keep in mind that radiators that aren’t heating properly may need bleeding, a process which can also lead to a drop in boiler pressure.

Boiler cutting out

A drop in boiler pressure will inevitably lead to system failure. If your boiler refuses to start at all or decides to have a little nap shortly after firing up, that could indicate a drop in boiler pressure.

How to fix low boiler pressure

Can I fix low boiler pressure myself?

The short answer is yes, you can. The slightly longer answer is yes, you can, but you should consult the manufacturer’s manual and be 100% sure that you know what you’re doing.

If there’s anything you’re the tiniest bit unsure about you should contact a qualified engineer.

Fixing low boiler pressure – step-by-step

  • Find your filling loop handles and boiler pressure gauge. You need to make sure you can see the pressure gauge while you access the loop.
  • Turn your boiler off.
  • Gently turn the handles 90 degrees until they match the direction of the pipe, which should start the flow of water.
  • Keep the handles in this position until the gauge shows that the boiler has been re-pressurised. (Remember that green zone we told you about?)
  • Once you’re happy with the pressure, return the handles to their original positions and check that they are properly closed.
  • Switch the boiler back on and pray that the pressure doesn’t drop again.
  • Make a cup of tea and run yourself a nice hot bath with water from your re-pressurised boiler.
  • That hasn’t worked – do I need a new boiler?
  • Maybe, maybe not. It can probably still be fixed for the time being, but there’s no guarantee that it won’t happen again in future.

Get in touch with a registered engineer and see what they think. If your boiler is on the blink, it could be time to think about getting a new one.

High boiler pressure

Less common than low boiler pressure but no less annoying is high boiler pressure. In fact, high boiler pressure can be even more damaging and tends to require more urgent action.

What causes high boiler pressure?

  • Too much water in the system
  • Faulty devices in the system failing to release pressure
  • Faulty filling loop
  • Natural expansion in an old system

How do I know my boiler pressure is high?

The obvious sign will be a boiler pressure gauge reading of 3 bar or higher – the red zone.

Another indicator can be found on the outside wall where your boiler is installed. When the pressure is too high the boiler’s safety pressure valve will start to drain water from the system in an attempt to bring the pressure down.

Pop outside and see if there’s anything leaking or dripping from the valve.

How to correct high boiler pressure

Just like us human beings, boilers also need a bit of a release when they’ve been under excessive stress. But boilers can’t go for a run or watch videos of puppies on YouTube to unwind.

The best way to reduce boiler pressure is to release water from the system. You can do that by finding a drain point – usually found underneath a radiator – and slowly opening it, allowing the water to drain somewhere safely.

As the water drains you can keep an eye on the pressure gauge to make sure you don’t accidentally drop the pressure below the safe zone.

None of this has fixed my boiler – what do I do now?

We’re sorry! If you were unable to correct your boiler pressure issues, then unfortunately your boiler might be on the way out.

Go and get a second opinion from a gas safe engineer, who will be able to tell you for sure whether you need a new boiler or whether your current one can be fixed.

Find me a new boiler!

Gladly. Using our innovative online system we can get a new boiler installed and get you warmed up within 24 hours.

Click that little button below and answer a few questions – we’ll suggest the best boilers and give you a fixed priced based on your circumstances. Choose your favourite and we’ll do the rest.

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