Glow Worm Boiler Pressure Guide: Correct Levels, Common Faults & Solutions

1. Check if the Issue is Minor or System-Wide

Before assuming a serious fault, assess whether the problem is localized or affects your entire system:

• Are radiators heating evenly?
• Is hot water available at all taps?
• Is the boiler displaying a warning or fault code?

If only part of the system is affected and the pressure is slightly low, it could be a minor issue. However, if the boiler shuts down completely or pressure continues dropping, the problem is likely system-wide and requires professional attention.

This initial check helps prevent unnecessary stress and guides whether a quick fixis possible or expert diagnosis is required.

2. Correct Glow Worm Boiler Pressure Levels

For most Glow Worm boilers, the recommended pressure is:

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

A small rise during operation is normal.

Warnings:

• Pressure below 1.0 bar is too low
• Pressure above 2.5 bar is too high

Both conditions can trigger a Glow Worm boiler pressure fault, which may cause the boiler to shut down to prevent damage or safety risks.

3. How to Check Glow Worm Boiler Pressure

Checking pressure regularly helps prevent unexpected breakdowns.

Steps:

1. Locate the pressure gauge on the boiler front or underside
2. Read the needle or digital display
3. Ensure the reading is within the safe range
4. Check again when the heating is running

If the gauge enters the red zone or displays a warning, action is required immediately.

4. Common Glow Worm Boiler Pressure Problems

Pressure issues are usually categorized as:

• Low boiler pressure Glow Worm
• High boiler pressure Glow Worm

Both can stop heating and hot water from functioning properly. Recognizing the type of pressure problem early can save time, prevent further damage, and reduce emergency repair costs.

5. Causes of Low Boiler Pressure in Glow Worm Systems

Low pressure means insufficient water circulation in your heating system. Common causes include:

• Bleeding radiators recently
• Small leaks in pipes or radiators
• Faulty pressure relief valve
• Recently serviced or drained system
• Worn seals or pipe joints

Signs of low pressure:

• Boiler shuts down unexpectedly
• No heating or hot water
• Pressure gauge reading below 1 bar
• Warning lights or fault codes

Ignoring low pressure can leave your Glow Worm boiler not working when you need it most.

6. Causes of High Glow Worm Boiler Pressure

High pressure usually occurs when there’s too much water in the system or a failure of internal safety components.

Common causes:

• Overfilling during repressurisation
• Faulty expansion vessel
• Malfunctioning pressure relief valve
• Blocked heating pipes

High pressure can lead to leaks, water discharge outside the property, and long-term boiler damage.

7. How to Repressurise a Glow Worm Boiler Safely

If your pressure is too low, repressurising the system can restore normal operation.

Safe steps:

1. Turn off the boiler and allow it to cool
2. Locate the filling loop beneath the boiler
3. Slowly open the valves
4. Watch the pressure gauge carefully
5. Stop at 1.2–1.5 bar
6. Close the valves securely
7. Restart the boiler

 Never overfill. If the pressure rises too quickly or drops again, professional inspection is required.

8. How to Reduce High Boiler Pressure

If your pressure is too high:

• Bleed a radiator using a radiator key
• Release small amounts of water until safe level is reached
• Monitor the gauge closely

Persistent high pressure may indicate a faulty expansion vessel, which requires a qualified Gas Safe engineer.

9. Why Glow Worm Boiler Pressure Keeps Dropping

If topping up pressure doesn’t solve the issue, there’s likely an underlying fault:

• Hidden pipe leaks
• Faulty pressure relief valve
• Failed expansion vessel
• Internal boiler component wear

Continuous pressure loss should never be ignored, as it can cause system failure and expensive repairs.

10. When to Call a Gas Safe Engineer

Contact OSO Group Engineers if:

• Pressure drops frequently
• Boiler pressure keeps rising
• Visible leaks from the boiler
• Fault codes appear repeatedly
• Heating or hot water stops completely

Note: Gas and internal boiler repairs should only be done by Gas Safe registered engineers to ensure safety and compliance.

11. DIY Checks vs Professional Repairs

Safe DIY Checks:

• Check boiler pressure gauge
• Top up pressure once if low
• Bleed radiators carefully
• Reset the boiler once (manufacturer advice)

Professional Repairs Required:

• Gas-related faults
• Internal boiler components
• Expansion vessel replacement
• Repeated pressure loss
• Electrical or control faults
  Attempting complex repairs yourself can be dangerous and costly.

12. Preventing Glow Worm Boiler Pressure Problems

Routine maintenance significantly reduces breakdowns.

Recommended steps:

• Annual Glow Worm boiler servicing
• Regular pressure checks
• Replace worn components early
• Keep heating system clean
• Address minor issues before they escalate

Routine care improves efficiency, safety, and boiler lifespan.

14. Final Thoughts

Maintaining correct Glow Worm boiler pressure is essential for safe and efficient heating. Low, high, or constantly dropping pressure can cause inconvenient breakdowns and costly repairs.

If your Glow Worm boiler is not working or pressure issues persist, professional help is the safest option. OSO Group Engineers provide expert, reliable solutions to keep your heating system running smoothly year-round.

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