Nobody wants their hot water supply or radiators to stop working. Unfortunately, incidents like this do sometimes occur and are often caused by a drop in boiler pressure. Depending on the cause, it is sometimes possible to correct a drop or increase in boiler pressure yourself, while other problems may require additional assistance.

What Should Your Boiler Pressure Be?

There is some variation in the recommended pressure of a boiler system depending on the make and model; however, a pressure reading of between one and one and a half bar generally suggests normal function. A reading below one bar indicates a problem and will normally cause your boiler to stop working. Similarly, a reading of above two and three-quarter bar indicates that the system is over pressurised. In this situation, it can be beneficial to bleed your radiators, as this will help to release some of the pressure and bring the system back down to a more normal level.

How to Resolve Low Pressure?

Should your boiler be suffering from low pressure and you are confident it is not as a result of a leak, then it is safe to repressurise your boiler system. If you are unsure about undertaking this task yourself, we would recommend hiring a Gas Safe Registered engineer to look at the system for you. However, it is also possible to tackle this problem on your own, as long as you stick to the following quick steps: Turn Off Your Boiler First, ensure your boiler is switched off before you begin to repressurise it. If possible, you should try and let the system cool for between four to six hours before starting this process.

Find the Hose

Next, check to see whether your boiler has an external filling loop. If it does, you may need to attach a braided filling hose here. Attaching a filling loop will enable you to add more pressure to the system. Some boilers have an internal filling loop, or a similar device used for the same function. If you are unsure, it is always best to refer to the manufacturer’s handbook for guidance.

Open the Filling Valves

Using either the installed tap handles or a screwdriver, start to open the filling valves on the boiler pipe work. As you turn the valves, you should begin to hear the sound of water running. Whilst doing this, keep an eye on the pressure gauge and ensure that the pressure is rising.

Close the Valves

Once the pressure gauge hits a reading of one bar it is time to close the valves off again. Try to not let the reading creep above one, as the pressure will still continue to increase slightly once the valves have been closed.

Switch the Boiler Back On

Wait for the pressure reading to settle, which can take a couple of minutes. Once it has, ensure that the reading is within a safe level of between one and one and a half bar and proceed to switch the boiler back on.

How to Resolve High Pressure?

Dealing with high pressure can be more tricky, as well as potentially more dangerous. Once again, it is not a job for everybody and might require the assistance of a qualified person to get right. If you are looking to do it yourself, you will need to try and bleed your radiators. We would recommend asking a second person to help you.

Cool Things Down

When bleeding a radiator, this can entail letting some excess water run out of it. Therefore, it is recommended that you let your system cool down before attempting to bleed resolve a high pressure issue so that the water is as cool as possible. You should let the system cool for four to six hours before starting the process.

Find the Key

Once the system has cooled, you will need to locate a bleed key, or radiator key. This is a small device that can be fitted to the top of a radiator and used to drain away pressure. Once you have a key to hand you can begin prepping for the bleeding process.

Protect Your Floor

Depending on how high the pressure is in your system, bleeding a radiator can be a messy process. That is why we would always recommend putting down some towels, or a dust sheet before starting. This way, you will ensure your floor is protected.

Bleed the Radiator

Fit the bleed key to the top of the radiator and slowly turn it until you can hear the sound of air, then water starting to be released. A small plastic tub is handy to catch the water as it comes out. If you have a second person helping you, then it is a good idea for them to stand near the pressure gauge whilst this is happening, to ensure you release the right amount of pressure. If you carrying out this task alone, then it is important to release pressure slowly, tightening the valve at intervals to allow you to check the gauge. You can then repeat this process until the issue is fixed.

Turn the Boiler Back On

Remember to check any valve you have worked with to ensure it has been retightened following the bleeding process. Check the gauge once more to make sure it is between one and one and a half bar. Once you are happy that your system pressure is at the right level then it is safe to turn your boiler back on.

When Should You Call an Installer?

We would always recommend hiring a Gas Safe Registered engineer if you are having any problems with your heating system, and this could include repressurising or bleeding your radiators if you do not feel comfortable attempting these tasks yourself. Similarly, should your boiler unit continue to lose pressure, or if the problem is not remedied by the methods identified in this article then we would recommend you call in a professional. Should you suspect that your boiler pressure has dropped as a result of a water leak then assistance should be sought as quickly as possible. Failing to do so can result in significant system damage, and ultimately affect the structural integrity of your home.


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