What is boiler pressure?
Boiler pressure is basically the pressure of hot water circulating through your central heating system.
It is important to maintain your boiler’s optimum pressure level in order for it to heat up your home and supply hot water efficiently. If the pressure is too high, there is a chance of leaks developing somewhere within your central heating system. If the pressure is too low, your home and hot water might take longer to heat up and your boiler will have to work harder to supply the central heating system with water, resulting in unnecessarily high energy bills!
What should my Baxi boiler pressure be?
Your Baxi boiler pressure will change depending on whether it is in use or not, but the normal operating water pressure for your boiler should be between 1.0 and 2.0 bar. You will be able to see the pressure level by looking at the pressure gauge on the front of your Baxi boiler.
When not in use
When your boiler is not in use, the pressure should be between 1 and 1.5 bar. If the needle on the pressure gauge is below 1 bar (in the red area of the pressure gauge), your boiler may not work and it will display an error code telling you that you need to top up the pressure.
When in use
When your boiler is in use, the pressure should not go higher than 2.5 bar. When your boiler is in use, the water in the system heats up and expands, causing the boiler pressure to increase but the needle on the gauge should still stay within the green area.
Why is my Baxi boiler pressure low?
There are two main reasons why your Baxi boiler pressure may be low:
You have recently bled your radiators
If you have recently bled your radiators, then water and trapped air has been released from the system, resulting in your boiler pressure dropping. The released air will need to be replaced with water in order to get the pressure back up. You can find out how to do this further down in this guide.
Leak in the central heating system
A leak in your central heating system reduces the amount of water flowing through it and results in the pressure dropping. A leak in your central heating system may be difficult to find, but you could conduct a visual inspection of the pipework and the radiators for leaking water or other signs of moisture.
Try not to confuse condensation on pipes or radiators in colder rooms with signs of a leak. If there is a leak in your system, you will need a professional to fix it.
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Other reasons why your Baxi boiler pressure is low
Your boiler may have lost pressure simply because it has been idle for a long time, like during the summer when you haven’t needed to turn on the heating.
Your Baxi boiler pressure may also be low because the expansion vessel inside your boiler needs recharging or replacing, or there could be debris inside the pressure relief valve. These are technical issues that only a Gas Safe registered engineer can solve.
Signs your Baxi boiler pressure is low
- Your radiators are not warming up properly
- There is no heating or hot water
- The needle on the pressure gauge has dropped below 1 bar and into the red area
- Your boiler is showing fault code e118 or e119
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How can I increase my Baxi boiler pressure?
Topping up your Baxi boiler pressure depends on the type of filling loop your Baxi boiler is equipped with. A filling loop is a pipe that connects the central heating system to the mains water supply and is used to fill your heating system with the water it needs to repressurise it.
Baxi have three different types of filling loops:
- Easyfill filling loop - A green lever
- Rigid filling loop - Two blue or black taps
- Flexi filling loop - A silver braided hose
Before taking any of the steps listed below to increase your Baxi boiler pressure, make sure you turn off the boiler from its mains switch, which is normally located on a wall near the boiler. After you have taken the steps, you can turn the boiler back on and continue to use it as normal.
I have a green lever
Have a look underneath your boiler. If you see a green lever on the right hand side, near the front of the boiler, then you have an easyfill filling loop.
To increase your Baxi boiler pressure, follow these three simple steps:
- Pull the green lever down. You should now hear water entering the central heating system.
- Keep an eye on the pressure gauge while holding the lever open to monitor the amount of water you are putting back into the system.
- Once the needle on the pressure gauge has reached 1 bar, let go of the lever.
I have two blue or black taps
If you look underneath your Baxi boiler and see two blue or black taps located on the right hand side, near the front of the boiler, then your Baxi boiler uses a rigid filling loop to repressurise the system.
If you have this type of filling loop, the first thing you need to do is make sure the taps are in the off position. To double check they are off, make sure the blue/black taps are pulled towards you.
Now that you have made sure the taps are off, follow these steps to repressurise your Baxi boiler:
- Unscrew the two brass caps that are screwed on the filling loops. These are the caps that are attached to a black rubber strap. If the screw is too tight, then use a spanner to unscrew it.
- Your Baxi boiler installer should have left with you a small copper bend that's attached to brass wing nuts and two rubber washers. If you can’t find these items, then check if they have been left on the top of the boiler or check if they’re with the boiler’s documentation.
- Attach the copper bend to both sides of the filling loop. With the rubber washers in place, tighten the brass wing nuts and make sure they are properly aligned.
If the rubber washers have been lost, DO NOT attempt to repressurise the boiler, as water will leak when you start repressurising the system. This could cause water damage to your property and could also damage the appliance.
- Now that the copper bend is in place, it is now time to let some water from the mains supply into the central heating system.
The blue/black tap on the left hand side of the filling loop is on the cold mains side. Push this tap away from you, towards the wall the boiler is mounted on. The blue tap should now be horizontally in line with the pipe, allowing the cold mains water to travel past this blue/black tap, arriving at the second blue/black tap.
- The water is now waiting for you to open the second blue/black tap on the right side of the filling loop, allowing the water to enter the central heating system. Slowly push the right hand tap away from you. You should now hear the water starting to flow.
- While the tap is open, keep an eye on the pressure gauge. Once the needle has reached 1 bar, pull the tap towards you to stop the flow of water into the heating system.
- Pull the tap on the left hand side towards you to stop the flow of water coming from the mains supply.
- Grab an old towel, as when you undo the wing nuts, the little bit of water that is left in the copper bend will trickle out. Now that you have your towel in place, undo the brass wing nuts, remove the copper bend and both washers, and keep them somewhere safe for the next time you need to increase your Baxi boiler pressure.
DO NOT open the tap fully as you are now in control of the amount of water going through your boiler system.
I can't see any levers or taps but I can see a silver hose
If you look underneath your boiler and don't see a green lever or two blue/black taps, then you probably have a flexi filling loop. The flexi filling loop is a silver braided hose and will be located near where your cylinder has been installed. You often find this type of filling loop when a system boiler has been installed and the filling loop is in a different location from the boiler.
To top up your Baxi boiler pressure if you have this type of filling loop, all you need to do is:
- If the flexi filling loop doesn’t have any taps or levers, then you will need a flat-head screwdriver. Now that you have your screwdriver, turn one of the valves (a slot at each end of the filling loop) on the flexi filling loop so that the line runs in line with the pipe.
- Now slowly turn the second valve on the other side of the flexi filling loop until you hear water flowing
- Monitor the pressure gauge and turn the first valve back to its original position once it has reached 1 bar. There should be a pressure gauge located near the cylinder and the flexi filling loop.
- Turn the valve on the other side back to its original position. Your Baxi boiler is now topped up.
Opening this first valve allows water to flow towards the second valve.
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Why is my Baxi boiler pressure high?
There are a number of reasons why your Baxi boiler pressure might be higher than it should be, but we’ll touch on the two main reasons that a homeowner may experience and be able to fix themselves.
The water pressure was topped up too much
Your boiler may have had low pressure and you used the steps highlighted in the previous section to increase the pressure. You may have topped up the pressure a bit too much and ended up tipping it over 2 bar.
As you will have read earlier in this article, when boilers are in use, the water in the central heating system expands, which results in a rise in pressure. So if you topped up the boiler beyond 2 bar, then the increase in pressure when it is in use could tip it over 2.5 bar and into the red area of the pressure gauge.
The filling loop is not completely closed
As you know by now, the filling loop is used to allow water from the mains into your central heating system so that you can top up your Baxi boiler pressure when needed. If the filling loop was not completely turned off, water from the mains will continue to fill up your central heating system. This continued water flowing into the system will raise the pressure in your boiler.
Other reasons why your Baxi boiler pressure is high
Your Baxi boiler’s expansion vessel may be faulty. An expansion vessel is a tank that is in all combi boilers. It contains water and air, and its purpose is to protect against excessive pressure by maintaining the right level of pressure in the boiler system. Too little air in the expansion vessel could result in your Baxi boiler pressure being too high. If there is a fault with your Baxi boiler’s expansion vessel, you will need a Gas Safe engineer to diagnose and fix the issue.
Signs your Baxi boiler pressure is too high
- The needle on the pressure gauge has risen above 2 bar and into the red area
- The boiler is showing fault code e117
How can I decrease my Baxi boiler pressure?
The best thing to do to reduce the pressure in your Baxi boiler is to bleed your radiators. Bleeding your radiator releases excess air that has been trapped inside the heating system.
You can easily bleed your radiators by following these few steps:
- Make sure your central heating system is turned off
- Place a jug underneath the bleed valve on the radiator to catch the water that will be released once you start bleeding the radiator
- Insert the radiator key into the radiator bleed valve and turn it slowly in an anti-clockwise direction
- Allow some water and air to be released from the radiator
- Close the valve by turning the radiator key clockwise
- Check the pressure gauge on your Baxi boiler. If it hasn’t gone down enough then you may need to bleed the radiator a bit more
- Once your Baxi boiler pressure is around 1.5 bar, turn your heating back on and check that the radiators are heating up properly
If you haven’t noticed that your boiler pressure has risen into the red area of the pressure gauge and haven’t taken steps to lower it, your Baxi boiler will discharge some water via its pressure relief valve. A pressure relief valve is a safety valve that opens if the pressure gets too high and closes again when the pressure returns to its normal level, in order to prevent the pressure in your central heating system building up to a dangerous level.
What can I do if I can't resolve my Baxi boiler pressure issue myself?
Although many Baxi boiler pressure issues can be resolved yourself, there are a number of technical boiler problems that could be the cause of high or low boiler pressure issues that can only be diagnosed and fixed by a Gas Safe registered engineer. Failing to get to the bottom of such issues could result in other boiler problems arising or even a boiler breakdown.
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