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Boiler Pressure Dropping? – Help

Boiler Losing Pressure

People experiencing their boiler pressure dropping is one of the most common issues that people have with their central heating system, but what causes it and might you have a water leak at your property? If so, how might we find the water leak in your central heating.

Boiler Pressure Fault

Clearly, if you think your actual boiler has a fault, we recommend speaking to your approved heating engineer who will be able to check your boiler for you. If you are looking for a boiler engineer – check the Gas Safe Register. There are a few boiler faults which can cause boiler pressure dropping (e.g. problem with pressure relief valve).

Boiler Pressure Dropping? – Pressure Gauge

Why are Boilers Pressurised?

This is a question that is often asked. Clearly there are a variety of boiler types and manufacturers, setup in different ways. However, central heating systems are generally sealed / closed systems circulating water around your property releasing heat to warm your home via radiators or underfloor heating.

Pressure is maintained in the system to help it operate efficiently in circulating the heated water around the property. Many boilers are setup so that when you have boiler pressure dropping below a certain level, they turn themselves off and so stop heating your home.

Why is my Boiler Pressure Dropping?

One of the possible causes of your boiler pressure dropping regularly is that water is escaping from the sealed system via a water leak, especially if it is happening regularly and / or rapidly. In fact, some boilers will give you specific error messages, such as F1 boiler fault or F75 boiler fault code, also an E119 fault code and additionally F22 fault codes to indicate you have a drop in pressure which may be caused by a leak.

As we said before, boilers generally need a specific pressure range to operate and have a safety cut off system which stops it running and circulating heated water around your system into radiators or underfloor heating pipes.

Plus as water leaks out of a system, often air can enter the system which can cause problems with the boiler, air locks and radiators needing bleeding. Clearly, if water is not getting into radiators, they will struggle to radiate heat.

Please note – with all these FAQs, do remember to check with your individual manufacturer guidelines / instructions. If in doubt, do get help when you have boiler pressure dropping.

What Pressure Should my Boiler be?

Always check your individual boiler manual or manufacturer guide online first. However, a lot of boilers recommend a range between 1.0 and 1.5 bar when cold or between 1.0 and 2.0 (sometimes up to 2.5 bars) bars when operating / warmed up. If you want to understand more about water pressure, it is explained in our article about water flow meters.

How Can I check my Boiler Pressure?

Most modern boilers have a visible pressure gauge on the front showing the pressure. Many also have green and red zones to indicate the optimal operating pressure for that particular manufacturers model. This can be verified in your manual or on the manufacturers websites.

Is my Boiler Pressure too Low?

Modern pressurised boilers tend to cut off at around 0.5 bar but this will depend again on the specific model, this then often triggers a warning or error message. As mentioned above, this may actually be shown on the boiler pressure gauge on the front of boiler, this can also allow you to track your boiler pressure dropping over time.

On this topic we have a helpful tool for when you have Boiler Pressure Low

How to Increase Boiler Pressure?

If you are unsure about how to do this or are not confident to follow your boiler’s instructions, then contact a Gas Safe Engineer. Otherwise, this can be a fairly straightforward task to carry out and your individual boiler make will have it’s own instructions or even a video guide on YouTube.

This normally involves the use of a mains water input valve, tap or key adding fresh water to the system to repressurise the boiler after boiler pressure dropping, using the pressure gauge to help. It’s recommended that you do this when the boiler is off and cooled down. Always make sure you do not leave the tap or valve on.

Boiler Pressure too High too Low
Is my boiler pressure too high?

Is my Boiler Pressure too High?

Again, check the acceptable / recommended boiler pressure with your manufacturers guides. In most cases, boilers will also shut-off if the pressure gets too high. Often this is in the range of 2.0 to 2.5 bars. Remember, this may be shown on the pressure gauge. Boilers most often also have pressure relief valves (PRV – also known as a pressure relief valves) on them as a s safety feature – when pressure gets above a pre-defined level.

Why is my Boiler Pressure Increasing?

There are a number of reasons your boiler pressure keeps rising and we recommend you get this checked professionally. However, assuming there isn’t a fault on your boiler (for example with the expansion vessel, filling loops PRV etc) or . It could be things like – too much water is in the system (remember that when they are running, boiler pressures generally rise from the expansion of the water in the system) or the water feed tap / valve has accidentally been left open – especially if you have used it recently.

Boiler Pressure Gauge
Boiler Pressure Gauges – Analogue vs Digital

How to Decrease my Boiler Pressure?

One common way to fairly simply reduce pressure on your boiler / central heating system, if you are confident and able to do so, is to bleed a radiator using a bleed valve (remember to have something to catch the water!). This will lead to boiler pressure dropping after releasing the water pressure until it is within normal operating range for your boiler. If you do accidentally over release the pressure it can be topped up again.

Should my Boiler Pressure Drop?

Clearly, other than when a boiler is cooling down, boiler pressure dropping wouldn’t be a normal everyday occurrence for a boiler to lose pressure. That said, it would not be exceptionally rare for pressure to drop and need a small top up. This is especially the case if, for example, it has not been used for a long time (e.g. over summer months) for central heating. Often people bleed radiators to release trapped air or repressurise their system to optimal levels.

As mentioned previously, pressure dropping repeatedly or rapidly could indicate either a boiler fault or a leak in your central heating system.

Remember the golden rule – if in doubt get help!

Central Heating Boiler Manufacturers

Here are some of the best central heating boiler manufacturers most often seen in the UK. We have included links to their websites so you can get recommendations and instructions for specific models in their range, including if you have boiler pressure dropping.

We hope you found our guide to boiler pressure dropping helpful.

Can boiler pressure drop without a leak?

Although water leaks are a common cause of boilers losing pressure, it can also be a fault with the boiler itself (such as the expansion vessel / valve). We have a guide to boiler leaks which might help. Leaks in your central heating pipes can be tricky to find so get help from a water leak detection expert.

What happens if your boiler has no pressure?

A boiler with no pressure isn’t necessarily something to get overly concerned about, especially with modern pressurised boilers which have safety mechanisms etc. When you have boiler pressure dropping, eventually it will go to zero. However, it will also likely stop your boiler working or make it run less efficiently so get help from a professional to help remedy it for you.