A Complete Guide to Glow Worm Boiler Pressure: Common Problems and Practical Solutions

Maintaining the correct Glow Worm boiler pressure is essential for keeping your heating system running safely and efficiently. Pressure problems are among the most common issues homeowners face, and they can lead to inconsistent hot water, heating failure, boiler lockouts, or error codes.

The good news is that many of these issues are easy to identify and, in some cases, can be resolved without major repairs. In this guide, OSO Group Engineers explain everything you need to know about Glow Worm boiler pressure, including the recommended pressure range, how to check it, common causes of low or high pressure, and safe solutions.

If you need expert assistance with your boiler, call OSO Group Engineers today at 020 4577 1229.

What Should Glow Worm Boiler Pressure Be?

For most Glow Worm boilers, the recommended operating pressure is:

• 1.0 to 1.5 bar when the system is cold
• Up to 2.0 bar when the heating is running

A slight increase in pressure during operation is normal. However, you should be aware of the warning signs:

• Pressure above 2.5 bar is too high and can damage your system
• Pressure below 1.0 bar indicates low water levels, which can cause the boiler to shut down

Both low and high pressure can affect your heating system’s performance, so it’s important to monitor pressure regularly and address any issues promptly.

How to Check Glow Worm Boiler Pressure

Checking your Glow Worm boiler pressure is simple and should be done routinely. Here’s how:

1. Locate the pressure gauge – typically found on the front control panel or beneath the boiler.
2. Read the gauge – when the boiler is cold, the needle should sit between 1.0 and 1.5 bar.
3. Check during heating operation – pressure may rise slightly but should remain below 2.5 bar.

If the needle moves into the red zone or the display flashes, this indicates a pressure fault that needs attention. Regular checks help prevent serious issues and ensure your boiler operates efficiently.

Common Causes of Low Boiler Pressure

Low boiler pressure usually means there isn’t enough water circulating in the system. This can happen for several reasons:

• Bleeding radiators – releasing trapped air reduces system pressure.
• Small leaks – leaks in pipework or radiators can lower water levels.
• Faulty pressure relief valve – a malfunctioning valve can release too much water.
• Recent maintenance work – topping up or draining the system incorrectly can cause pressure issues.

Signs of low pressure include:

• No heating or hot water
• Boiler shutting down unexpectedly
• Warning lights or error codes on the display

Addressing low pressure promptly prevents further damage and ensures your heating system continues to operate safely.

How to Repressurise a Glow Worm Boiler Safely

If your boiler pressure is too low, repressurising can often restore normal operation. Follow these steps carefully:

1. Turn off the boiler and allow it to cool.
2. Locate the filling loop beneath the boiler.
3. Open both valves slowly to let water enter the system.
4. Watch the pressure gauge carefully.
5. Stop when the pressure reaches 1.2–1.5 bar.
6. Close both valves tightly.
7. Restart the boiler.

 Always increase pressure gradually. Overfilling can lead to high boiler pressure, causing leaks or system damage. If you are unsure or uncomfortable, contact OSO Group Engineers for safe assistance.

Common Causes of High Boiler Pressure

High boiler pressure is often caused by too much water in the system or a faulty internal component. Common reasons include:

• Overfilling during repressurisation
• Faulty expansion vessel
• Malfunctioning pressure relief valve
• Blocked or restricted pipework

Ignoring high pressure can result in leaks, boiler lockouts, or long-term damage to internal components.

How to Reduce High Boiler Pressure

If your boiler pressure is too high, you can reduce it safely by:

1. Bleeding a radiator using a radiator key.
2. Releasing small amounts of water until pressure drops to around 1.5 bar.
3. If pressure rises again shortly after, it may indicate a faulty expansion vessel or valve, requiring professional repair.

Regular monitoring and proper maintenance can help prevent recurring high pressure issues.

Flashing Pressure Warning Indicators

A flashing pressure indicator on your Glow Worm boiler is a warning sign that should never be ignored:

• Flashing low pressure: the system needs repressurising.
• Flashing high pressure: the system may require venting or component inspection.

Continuing to use the boiler without addressing these warnings can lead to breakdowns or safety risks.

Why Does Boiler Pressure Keep Fluctuating?

Some pressure movement is normal, especially when heating cycles on and off. However, constant or sudden changes indicate a problem.

Possible causes include:

• Small, hidden leaks
• Air trapped in radiators
• Faulty pressure relief valve
• Expansion vessel failure

If your boiler repeatedly loses pressure after topping up, professional diagnosis is strongly recommended. OSO Group Engineers can identify and fix the root cause.

When to Call a Boiler Engineer

You should contact a certified boiler engineer if:

• Pressure drops repeatedly after repressurising
• Pressure rises into the red zone frequently
• Leaks are visible around the boiler
• The boiler displays error codes or shuts down
• You hear unusual noises like banging or gurgling

A qualified engineer can safely identify faults, replace components, and ensure your Glow Worm boiler operates reliably and safely.

The Importance of Regular Boiler Servicing

Regular servicing plays a key role in preventing pressure-related problems. Benefits of annual maintenance include:

• Early detection of leaks and worn parts
• Improved energy efficiency
• Reduced risk of breakdowns
• Extended boiler lifespan

An annual service ensures your Glow Worm boiler remains safe, reliable, and compliant with regulations, giving you peace of mind all year round.

Why Choose OSO Group Engineers?

At OSO Group Engineers, we provide expert boiler and heating services, including:

• Glow Worm boiler repairs
• Boiler pressure fault diagnosis
• Annual boiler servicing
• Emergency heating support

Our experienced engineers deliver reliable, safe, and professional solutions, ensuring your system runs efficiently and meets all safety standards.

📞 Call OSO Group Engineers today at 020 4577 1229 for expert assistance.

Conclusion

Maintaining the correct Glow Worm boiler pressure is crucial for comfort, safety, and efficiency. By understanding how to check your pressure, identifying low or high boiler pressure, and taking appropriate action, you can prevent many common heating issues.If you ever notice persistent pressure problems or are unsure about performing maintenance yourself, professional help is the safest option. OSO Group Engineers are ready to help keep your heating system running smoothly and reliably.

FAQ