Your home’s boiler is arguably its most important appliance, ensuring hot water and heating to keep you comfortable all year round.
Whether it’s powering your shower or ensuring radiators can provide you with warmth during those chilly winter nights, boilers play a crucial role in your everyday life.
However, for a boiler to work efficiently it must always maintain the correct pressure. When boiler pressure drops too low out of the recommended range, it can cause a wide range of issues including poor heating performance and, in severe cases, complete system failure.
If you’ve found yourself having to constantly top up your boiler or are wondering why it keeps losing pressure, you’re not alone. It’s a common issue and in this blog, we’ll explore some of the main reasons why a boiler may lose pressure.
Read on for more information…
What Is Boiler Pressure?
Boiler pressure refers to the pressure of hot water that is circulating in your central heating system. Unlike older heating systems that used to rely on gravity-fed systems, most modern boilers use pressure to circulate the hot water through your radiators and pipes. The pressure is maintained in bars and can be read on a pressure gauge that is usually located at the front of your boiler.
When your boiler is working normally, it will maintain a consistent pressure that allows the system to efficiently heat your home. If the pressure becomes too high or too low, it will begin to operate inefficiently and, if not fixed, can cause damage to the boiler.
It’s also worth noting that prolonged pressure issues can decrease your boiler’s lifespan and lead to costly repairs or even a replacement.
What Should Boiler Pressure Be?
For most boilers, the optimal pressure is between 1.0 and 2.0 bars when the central heating system is on and 1.0 to 1.5 bars when it is off.
However, every boiler is different, so you should check the manufacturer’s guidelines or your boiler’s user manual for the exact pressure required for your specific type. If your boiler is consistently operating outside of this desired range, it can cause a whole host of problems including leaks, damaged components or even a complete boiler breakdown.
Low pressure usually indicates a problem within the system, whereas high pressure can result from overfilling or problems with the faulty expansion vessels. We’ll go into this in further detail later in the article.
What Happens If A Boiler Is Low pressure?
When your boiler’s pressure drops below the recommended level, it can have a range of negative consequences including:
- Inefficient heating: Radiators may take longer to warm up, or they may not heat up at all. This can result in increased energy usage and higher bills as the system needs to work harder to operate.
- No hot water: If your boiler is a combi boiler, you might find that your hot water supply is impacted. This can be frustrating and unpleasant, especially during the colder months when hot water is essential.
- Boiler shutdown: Many modern boilers have built-in safety mechanisms that shut the boiler down if the pressure drops below a certain level. This is to stop the boiler from doing irreparable damage to itself. If your boiler is shutting down on a frequent basis, it is a sign that something is wrong.
While you can manually repressurise a boiler to counteract low pressure, if it is a continuous problem it is a sign there is a more significant issue that needs to be fixed.
What Happens If A Boiler Is High Pressure?
In contrast, high pressure in a boiler is an equally big problem. If your boiler pressure is continuously rising above 2.0 bars (or even 2.5 bars) it can cause issues such as:
- Leaks: Excess pressure can force water to escape from the system. This will happen in weak joints, valves and other areas.
- Damaged components: Continuous high pressure can put a strain on seals, valves and other internal components. This can cause premature wear and tear and long-term damage.
- Boiler shutdown: Just like with low pressure, many boilers will automatically shut down if the pressure becomes too high. This safety feature is designed to prevent damage and stop the boiler from becoming a hazard.
- Boiler explosion: If your boiler does not have a shutdown feature, the continuing high pressure can even cause it to explode in severe cases. This is a major hazard that can cause harm to those in the vicinity.
It’s important to promptly address high pressure issues to avoid costly repairs and serious issues. If you’re unsure of how to rectify a problem, always consult professional support.
Why Does My Boiler Keep Losing Pressure?
If you find yourself frequently needing to top up your boiler’s pressure, you should try and determine the underlying cause. Some of the most common reasons include:
Radiator Bleeds
Bleeding your radiators to release trapped air can occasionally cause a drop in pressure. When the air escapes, it’s replaced by water from the system, reducing the overall pressure. While bleeding radiators are a necessary task, it should usually only be required once a year. If you over bleed them, it can cause the system to underperform and you should always monitor the boiler pressure when you do this job.
Leaks
One of the most common reasons for pressure loss is leaks. Visible leaks can happen around pipe joints, valves or the boiler itself. Check all visible piping and connections for any signs of moisture, rust or corrosion. Even minor leaks can cause significant pressure drops over time.
Hidden Leaks
Not all leaks are obvious. Sometimes, leaks can occur in hidden or inaccessible areas. These hidden leaks can happen due to low pressure, but they can be extremely challenging to detect and often require professional expertise to identify them. Signs of hidden leaks include damp patches, musty odours or mould growth in your home.
Faulty Pressure Relief Valve
If your boiler’s pressure relief valve is malfunctioning, it can cause the pressure to continually drop. This may be due to debris, corrosion or simply wear and tear.
How To Check My Boiler Pressure?
Every boiler will come with a pressure gauge. Located on the front of the boiler, it will allow you to check the pressure of the boiler and take any remedial action that may be needed.
How To Fix Low Boiler Pressure?
If your boiler pressure has dropped, you can manually restore it to a suitable level.
First, locate the filling loop. This is a sliver, flexible pope that features two valves. It can usually be found on the underside of your boiler.
Using a flat-head screwdriver, turn the isolation valve anti-clockwise until the line on the valve aligns with the line on the pipe. Next, turn the handle valve anti-clockwise and this should allow water into the system. As you’re doing this, monitor the pressure gauge. Once the gauge reaches the recommended level, you can switch both valves off.
Sometimes, boilers will come with fault codes that outline a problem has occurred. This may alert you to the fact that the pressure has decreased.
If you’re having to constantly increase the pressure of your boiler, this is a sign that a more serious problem has occurred and you should seek professional support.
Common Boiler FAQs
Here are some of the most frequently asked questions regarding boiler pressure:
How Often Should I Check My Boiler Pressure?
Ideally, you should check your boiler pressure once a month to make sure everything is operating smoothly. In addition to this, if you start noticing issues with heating or hot water, you should also take the time to check the pressure.
Can A Faulty Thermostat Cause Pressure Loss?
While it’s unlikely, a faulty thermostat can occasionally cause a system to overwork. This might indirectly affect the boiler pressure but it is more likely to be another issue.
Is It Safe To Use A Boiler With Low Pressure?
No, operating a boiler with low pressure can damage the system and reduce its efficiency. Furthermore, it can cause issues that may impact the safety of those in the property. Therefore, it’s best to address the issue as swiftly as possible.
Why Does Boiler Pressure Drop Overnight?
Overnight, water can cool and contract within the boiler’s system. This can increase the likelihood of problems and make the pressure drop.
Can I Fix Boiler Pressure Issues Myself?
Sometimes, minor issues can be fixed by simply topping up systems. However, more complex issues should always be handled by professionals.
Understanding why your boiler keeps losing pressure is essential for maintaining a comfortable and safe home environment. While some issues can be resolved with simple DIY methods, recurring problems may indicate deeper issues that need professional attention. By regularly maintaining the system and taking prompt action if you notice an issue, you can ensure your boiler continues to function efficiently and safely for years to come.
If you’re struggling with ongoing low pressure issues, it’s best to consult accredited engineer who can help.
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