Boiler Pressure Too High: Causes Of High pressure In Boilers & How To Fix

James Elston
Written by James Elston
Updated on 27th February 2024
Posted on 17th January 2024
Boiler Pressure Too High: Causes Of High pressure In Boilers & How To Fix

Is your boiler pressure too high? Here is how to reduce the pressure in your boiler

inside combi boiler to check pressure

High boiler pressure can be worrying to anyone who isn’t a gas engineer, but first things first, it’s highly unlikely to be a risk to your safety.

Need a new boiler? Get a fixed price in 20 seconds here

While it is true that both high and low boiler pressure can cause efficiency or maintenance problems, it’s very unlikely to cause any problems besides maintenance.

So, take a breath and then jump into our guide on what to do when your boiler pressure is too high and we’ll explore the basics, how to read your pressure, what boiler pressure is best, and what could be causing problems.

Get an online fixed price in 20 seconds:

What kind of fuel does your boiler use?

Get an annual service quote here – if you want a Gas Safe boiler service nationwide from Boiler Central

Book my service

What is boiler pressure?

The pressure of the hot water inside your central heating system is known as boiler pressure. While the intensity and speed of water flow from the faucets and shower.

Your boiler warms the cold water before distributing it throughout your home’s network of pipes and radiators. 

The appliance must have sufficient pressure to “push” the water for it to function properly. 

In contemporary combi boilers, a filling loop that is linked to the cold water supply regulates the pressure.

Our Expert Gas Safe Engineer Says:

Boiler pressure is important to make sure your boiler is working as it should be. High boiler pressure can be dangerous and if bleeding your radiators doesn't keep the pressure down, make sure you contact a Gas Safe heating engineer like me ASAP.

James Murfin

Gas Safe Registered Heating Engineer

How to Check Boiler Pressure and What It Should Be?

The boiler pressure is typically between 1.0 and 1.5 bars, as a general rule. If you’re unsure how to check the boiler pressure, just follow these simple steps:

  • To begin with, you must find the boiler’s pressure gauge. Typically, it’s on the appliance’s front.
  • There will be two coloured portions on the pressure gauge: a red area and a green section.
  • The gauge’s needle will typically be below the green part if the pressure is too low, or less than 1.0 bar, and in the red portion if the pressure is too high, or greater than 2.5 bars.

Why is high boiler pressure a problem?

Put simply, boiler pressure is the balance of water and air inside the boiler system.

boiler pressure

This includes the pipes as well. High boiler pressure means that there is an imbalance, and your boiler needs to release some pressure to ensure it is working properly and efficiently

Balanced boiler pressure is necessary if you want to heat the water that travels around your home effectively and efficiently and if your boiler pressure gets too high then your boiler will lock out leaving no hot water from your boiler at all.

Is high boiler pressure dangerous?

Potentially as it can lead to water leaks around your home and electrics. High pressure on your boiler can cause efficiency problems which will cost you money on your gas bill.

A pressure relief valve should kick in if boiler pressure goes high, but if this valve does not kick in, it can become dangerous. Other than a leaking boiler, high boiler pressure can also cause other boiler problems like parts in your boiler breaking such as the heat exchanger or any fixings.

boiler pressure gauge

Boiler pressure too high doesn’t sound good, does it?

You might have seen cartoons or other slightly less realistic TV programs where too much pressure results in the boiler exploding, but it can’t be that serious, can it?

Yes, that is exaggerated, but too much pressure in your boiler is not good and if bleeding your radiators doesn’t work, then you must call a Gas Safe registered engineer.

My Boiler Pressure Is Too High?

What happens if the pressure is too high on your boiler?

You might be thinking “is your boiler pressure too high – how am I supposed to know?”. Boiler pressure should be between 1 bar and 2 bar. This is usually around 10 o’clock on most boiler pressure gauges.

If that was your first thought reading the title don’t worry because reading the pressure is quite easy.

That’s what the boiler pressure gauge is for after all.

This gauge will often have numbers and colours so you can tell at a glance whether the pressure on the boiler is too high or low. It should be around the 1.5 bar mark. More modern boilers have a green part that shows where your pressure gauge needle should be.

Why is my boiler pressure too high? 

If your boiler pressure is too high then there could be multiple different causes.

Sometimes these boiler problems will be easy to fix, and you can even do it yourself without a Gas Safe heating engineer.

It could also be a much more complicated issue so let’s look at some of the common causes of boiler pressure problems.  

1. Boiler Age

If your boiler is over 10 years old and you are experiencing pressure problems, then there is likely a connection.

Boilers do naturally experience wear and tear and performance issues as they get older (don’t laugh) and will usually suffer from pressure problems.

So, in these cases, upgrading to a new boiler is recommended. Repairs might patch the problem for a while, but they aren’t going to be a long-term solution. Eventually, it could end up costing you more money.

If you need a new boiler, take a look at our guide to the best combi boilers, best system boilers or regular boilers.

Get an online fixed price in 20 seconds:

What kind of fuel does your boiler use?

We have great boiler deals, and offer finance on a range of boilers, all from £9.50 to £17 per month on a replacement boiler.

If you have a back boiler, then we will struggle to help you, but you may find our back boiler replacement guide helpful.

2. Faults and Malfunctions 

There are numerous components in a boiler-related to measuring/ dealing with pressure. If these get damaged in some way or malfunction, then your boiler’s pressure could easily rise or have no boiler pressure.

gas safe installer

The pressure release valve and filling loop are the two most common culprits for boiler pressure.

You can inspect these yourself but in the majority of cases calling in a professional Gas Safe heating engineer is advised unless you know what you are doing.

The good news is if the issue is quick and simple, it might not cost much to fix although if you need replacement parts, it will be more expensive.

Always remember you may have a warranty to cover the issue. Whether your Worcester Bosch boiler pressure gauge is not working, Vaillant boiler pressure is too low, or Baxi combi boiler pressure is too high, it is always worth checking the warranty.

3. Too Much Water

Can a boiler have too much water?

boiler leaking water

That might sound like a riddle, but the answer is yes, your boiler can have too much water. If it does, it can cause problems, especially where pressure is concerned.

But going from too little water to too much water is still a problem, isn’t it?

Is your boiler leaking water?

To diagnose this problem, you simply shut the boiler off and see what the pressure gauge says. If the boiler pressure gauge reads 1.5 or more, then you likely have too much water in the system.

But how do you release too much water from the system?

Thankfully realising boiler water pressure from the system is quite simple and in most cases simply bleeding your radiators will get rid of the excess water and return the normal boiler pressure.

It might sound painful but all you have to do is turn the safety valve a little on your radiators and let some excess water drip out.

Monitor the gauge while doing this and stop when it reaches back into the safe green zone.

Error Codes for High Boiler Pressure

ideal boiler error code

Before you go and inspect your boiler pressure gauge because this blog has probably made you a little anxious.

You should know that many modern boilers will also run error codes on their control panels. Error codes run if they are detecting problems with the boiler pressure.

Keep your boiler instruction manual handy or be prepared to search online for it. If both of the above fails, you can call the manufacturer if you spot some error codes and think they relate to your boiler’s pressure.

Error codes are a great way of catching a problem early that might not show up on the pressure gauge right away.

Your boiler pressure may be high but this could be a simple fix rather than a new boiler installation

Get an online fixed price in 20 seconds:

What kind of fuel does your boiler use?

We have great boiler deals, and offer finance on a range of boilers, all from £9.50 to £17 per month on a replacement boiler.

If you have a back boiler, then we will struggle to help you, but you may find our back boiler replacement guide helpful.

How risky is high boiler pressure?

boiler overflow pipe leaking

Exploding boilers like I said earlier are pretty much the work of cartoons and dramatic movies.

High pressure doesn’t equal instant boiler explosion.

Most boilers that have too high pressure will shut down due to the pressure release valve or just break down because they can’t handle the stress (yeah we can all relate to that can’t we).

They will likely spring leaks and might soak your carpet or kitchen, but usually, there will not be a huge explosion.

What to do if your boiler pressure is too high and can’t be fixed?

boiler cover (service)

If your boiler is on the blink and you think that you need it fixed, contact a Gas Safe heating engineer or firstly check your manufacturer’s warranty to see if you are covered.

Alternatively, you may need a new boiler.

We can offer boilers on finance or cash outright with a fixed online boiler quote within minutes.

We can, however, help you if you require a combi boiler conversion or a system boiler swap. 

How to keep your boiler from breaking down in the future:

An annual boiler service is the best way to avoid costly, inconvenient, and even dangerous boiler faults. In fact, you should have all gas appliances in your home safely checked and serviced on an annual basis by a Gas Safe registered engineer.

boilers on finance

Expect the cost of a boiler service to be around £100 but this will save you money on your gas bills as it keeps your boiler energy efficient.

High pressure can damage your boiler in a variety of ways, including leaks in the system and a build-up that can eventually cause permanent damage.

Why wait and watch your boiler break down? We provide boiler cover with free annual boiler servicing, so you can rely on us to assist and check your boiler on a regular basis instead of making a yearly appointment.

Do you have Low boiler pressure?

If the boiler pressure is too low this will also cause issues like your boiler shutting down or not passing hot water around your central heating system. be possible and can cause several other problems.

In fact, boiler pressure that’s too low or high is one of the most common reasons people replace and upgrade to a new boiler. But it’s not always necessary.

First, take a look at the questions that are relevant to your situation below.

Get an online fixed price in 20 seconds:

What kind of fuel does your boiler use?

What is the ideal boiler pressure?

The green 1 – 1.5 bar is the safe spot where you want to be.

boiler pressure
  • If you are hitting over 2.5, then you have too much pressure in your boiler.
  • If you are below 1 you have low boiler pressure.

read more on what your boiler pressure should be and why here.

While gauges will go higher in most cases, a boiler will shut off or break down if the boiler pressure is rising to 3 bar or 4.

However, if for some reason it hasn’t, and it doesn’t lower after a while, then you should shut the boiler off for your own safety.

If you do see the boiler pressure is too high when you have heating on don’t worry straight away.

If your boiler is busy heating up and someone is cleaning the dishes, someone’s taking a hot bath, and you have your radiators on then the pressure will naturally be higher. Sometimes it might even hit the 3 – 4 zone on the pressure gauge.

Don’t worry, though because this just means the boiler is currently experiencing a high water demand.

Once people turn off the hot water and radiators cool down the gauge will return to the more comfortable levels.

However, if you are constantly seeing boiler pressure rising to 3 bar which is classed as high-readings and you aren’t placing a higher demand on your water, then what could the problem be?

Well let’s go back to the first question I asked “Is your boiler pressure too high?”

If your boiler pressure is too high and there is no way it could be because of normal usage then it will likely be because of a fault.

Let’s look at some of the common causes in more detail.  

How to release pressure from a boiler

Often a pressure release valve can fix your problems, but if not, releasing pressure from your boiler can be done simply by bleeding your radiators.

If you have ever bled your radiators before then you will know you usually have to top up your water pressure on the boiler afterward at some point.

This is basically the same. This may solve your problem, but if your pressure becomes high again quickly, you will need a heating engineer to check your system.

Boiler Pressure – Summary

  • You may always attempt to re-pressurise your boiler by adhering to the directions we offered you if you can’t find a leak or there aren’t any indications that a boiler component is broken.
  • It’s always advisable to have a professional check out your appliance to see why it’s losing pressure because it may be quite dangerous to try to repair or replace a boiler part on your own.
  • If your boiler is causing you persistent problems, think about obtaining a new boiler because getting a part changed might occasionally be more expensive.
  • Although it is not always a serious problem, high pressure in your boiler can be. Because of this, you should monitor the pressure and take immediate action to fix the issue if it does start to rise.
  • Check the pressure gauge on your boiler frequently to look out for low and excessive pressure.
  • To top off for low pressure, use the filling loop.
  • Before making a potentially expensive repair, bleed the radiators if there is a minor increase in pressure when your boiler is off.
  • Never perform any further maintenance on a boiler and contact an engineer if you have any doubts.
  • To remove sludge from your boiler, a possible source of blockages and corrosion, consider doing a deep clean, or power flush.

Get an online fixed price in 20 seconds:

What kind of fuel does your boiler use?
Written by
James Elston
James Elston Director Of Boiler Central
Posted on: 17th January 2024

James Elston is our resident boiler replacement and heating expert here at Boiler Central. With over 20 years experience in the boiler installation industry, James ensures that he knows everything there is about our Gas Safe boiler installations, energy saving and home heating solutions. This can be from simply procuring the latest best combi boilers, to reviewing and ensuring that Boiler Central maintains the highest standards across our boiler installation company.

Buy a new boiler in minutes

Instant online quotes. Nationwide next-day fitting

Get my fixed price
Get a great price on a Which? Best Buy boiler online in 20 seconds
  • Over 15,000 boilers installed
  • Rated Excellent on Trustpilot
  • Fair, fixed and final prices
  • No pushy salespeople
  • Next-day installation
  • 0% deposit interest-free finance
Next-day fitting available until 2pmGet a quote now >