A boiler can lose pressure for several reasons, from a faulty internal component to a leak in the system.
Your boiler needs to maintain a stable pressure to function and work as efficiently as possible. But a boiler can lose pressure due to faults or leaks, which affects its performance and leads to no heating or hot water. If your boiler keeps losing pressure, you need to investigate the situation and identify the cause to determine what you need to do next to solve the problem.
Boiler pressure explained
Most modern boilers are sealed systems that don’t require an expansion tank in the loft, so the volume of water remains constant. Maintaining a constant boiler pressure is essential for keeping water flowing through your heating system and around your home. If you have a modern combi boiler, you can maintain the pressure by using a filling loop that connects to your water pipes.
Low boiler pressure will prevent your heating from working and make your system shut down, and high boiler pressure will result in efficiency problems and cause your system to overwork and even fail.
Although the ideal boiler pressure is usually between 1 and 2 bars, some boilers have different pressure requirements. You can check your boiler manual to find out the correct pressure for your boiler, and then look at the pressure gauge on your boiler to see if it’s losing pressure.
Is low boiler pressure dangerous?
The good news is that low boiler pressure is not dangerous. Any boiler, be it an Ideal, Vaillant or Worcester Bosch boiler, can lose pressure. Low boiler pressure is usually nothing to panic about, but it can affect the efficiency of your central heating system and cause boiler problems.
In most cases, the boiler needs to be re-pressurised to put things right, which you can do if you feel comfortable doing so. If you have concerns or don’t want to top up the pressure yourself, it’s best to contact a Gas Safe registered engineer.
How to top up your boiler pressure
You can top up your boiler yourself but always check the instructions in your manual first. If you can’t find the manual that came with your boiler, you might find the information you need by visiting the manufacturer’s website.
Topping up your boiler is a simple process that typically includes the following steps:
Step 1 – Locate the filling loop
When using a filling loop to top up your system, you must turn off your boiler and make sure the system is cold. The filling loop is the flexible silver pipe that’s underneath your boiler and usually has taps at both ends, but sometimes only has one tap.
Step 2 – Add pressure
Make sure you can see the pressure gauge before you increase the pressure. To add pressure, you need to open the taps at either end of the filling loop to let water into your system. Turn the taps, one after the other, and keep an eye on the pressure gauge whilst you turn them. Once the gauge reaches between 1 and 1.5 bar, you can close the taps.
Step 3 – Switch on your boiler
Your boiler has been re-pressurised, so you can now switch on your boiler. If it doesn’t work once you turn it back on, check your manual to see whether you need to press the reset button to resume normal operation.
My boiler is still losing pressure
If your boiler keeps losing pressure after you top up the system, it may be a sign of a serious problem. Below, we explain the most common reasons for a boiler to lose pressure.
1. Boiler leak
A leak is one of the most common causes for a boiler losing pressure. A boiler leak can happen when internal components age or loosen, but it can be hard to spot because the water doesn’t always leak from the bottom of the appliance.
The solution: You shouldn’t ever remove the boiler casing yourself, so you need to call a Gas Safe registered engineer. They can inspect your boiler to see if any parts are faulty and causing a leak, then advise you on what needs repairing or replacing.
2. System leak
Another common culprit for a boiler losing pressure is a leak somewhere in your system. If the system is leaking, you may have trouble finding the leak because some parts of your system are not easily accessible. What you can do is check all the radiators and visible pipes in your home for signs of leaks and inspect your walls and ceilings for damp patches.
The solution: Fixing a system leak is a job for a qualified Gas Safe registered engineer. The engineer will inspect your system and carry out the necessary repairs to prevent further damage and get things back up and running again.
3. Faulty boiler part
Boiler parts can sometimes become faulty, especially for old boilers, and need repairing or replacing. If there is a fault with an internal part of your boiler, an error code may appear on the display panel to warn you that something is wrong and needs attention.
The solution: It’s impossible to know for sure whether a part is faulty without removing the boiler casing and carrying out an internal boiler inspection, which are things only a Gas Safe registered engineer should do.
Should I replace my boiler?
Sometimes getting an engineer to repair your boiler or replace parts can be more expensive than buying a replacement boiler. If your boiler regularly plays up or breaks down, you should consider investing in a new one.
Feel free to browse our website to get a better idea of how much you can expect to pay for a new boiler from your preferred brand. You can also complete our online form to receive free quotes from different trusted companies and compare the price of a new boiler and the installation.
Read on to discover the common causes of a boiler lockout and the steps you need to take to solve it.