Glow-Worm Boiler Error Codes Explained: Causes and Fixes

The most common Glow-Worm boiler error codes include F22 for low water pressure, F28 for ignition failure, F75 for pump or pressure sensor problems, and F29 for flame loss.

These codes help homeowners and landlords understand issues in their central heating setups quickly. 

Glow-Worm Boiler Error Codes: A Quick Overview

Glow-Worm boiler error codes use F numbers to clearly indicate specific faults across popular models like Betacom and Ultracom, helping you manage your home heating system effectively.

This table covers the most reported Glow-Worm boiler error codes. Check your model manual for full details.

Glow-Worm Boiler Error Codes: Causes & How to Fix

Glow-Worm boiler error codes stem from everyday situations like pressure changes, cold weather, and normal wear in UK homes. Here are detailed explanations and safe steps for the most common ones.

F22 Low System Water Pressure

This Glow-Worm boiler error code means the water pressure has dropped too low for safe running. It is one of the most common and usually fixable at home.

Common causes include small leaks from radiator valves or pipe joints that develop over time, air entering the system after bleeding radiators, a faulty expansion vessel that no longer holds pressure properly, or gradual natural loss in older systems, particularly in properties with hard water that can cause slow corrosion.

Step-by-step fixes:

1. Locate the pressure gauge on the front of your boiler, usually a dial or digital display. Note the reading when the heating is off and the system is cold. It should normally sit between 1 and 1.5 bar.
2. Find the filling loop, typically a flexible silver braided hose with two lever valves connected near the bottom of the boiler.
3. Ensure both valves on the filling loop are closed initially. Slowly open one valve then the other while watching the pressure gauge closely. Add water gradually until the gauge reaches about 1.2 to 1.5 bar.
4. Close both valves firmly in the opposite order. Run the hot water tap briefly or bleed a radiator or two to release any excess air that may have entered during filling.
5. Check the pressure again after a few hours of heating use. Walk around and check under radiators and near pipes for any damp patches or leaks. If the pressure keeps dropping, call a Gas Safe engineer to locate and repair the source.

F28 Ignition Failure

This code shows the boiler cannot light or detect a flame. It is frequent, especially in winter.

Causes include frozen or blocked condensate pipes that prevent proper drainage and cause backup, interrupted or low gas supply from meter issues or external pressure drops, dirty or worn ignition electrodes that fail to create a strong spark, problems with the gas valve not opening fully, or blockages in the flue or air intake that affect combustion.

Step-by-step fixes:

1. Test other gas appliances such as the cooker hob to confirm the overall gas supply is active and working normally.
2. Go outside and carefully examine the condensate pipe (the small plastic pipe exiting the boiler). Feel for ice buildup, especially during freezing weather. Thaw it gently by wrapping with old towels soaked in warm water or using a hot water bottle filled with lukewarm water. Avoid boiling water or direct heat sources.
3. Check that the gas isolation valve near the boiler is turned fully open (in line with the pipe).
4. Switch the boiler off at the mains electrical supply, wait a full 30 seconds, turn it back on, and press the reset button.
5. Observe during the next heating cycle. If the same code returns quickly, stop further resets and contact a Gas Safe registered engineer who can safely examine the ignition electrode, clean the burner, and test the gas valve.

F75 Pump or Pressure Sensor Fault

This Glow-Worm boiler error code indicates no pressure change when the pump runs.

Causes include a seized or failing circulating pump that no longer moves water effectively, airlocks or sludge buildup restricting flow in older systems, a faulty pressure sensor giving incorrect readings, or problems with the diverter valve in combi models.

Step-by-step fixes:

1. Check and top up the system pressure using the filling loop method described in the F22 section.
2. Bleed several radiators thoroughly to remove trapped air, starting from the highest points in the house.
3. Listen near the boiler for the pump running when heating is demanded. Note any unusual humming, grinding, or complete silence.
4. Reset the boiler after these actions.
5. If the fault persists, an engineer should test the pump, sensor, and overall circulation thoroughly.

F29 Flame Loss

The boiler lights but then loses the flame with this code.

Causes include unstable gas pressure from supply fluctuations, partial blockages in the flue or condensate system, sensor issues that misread the flame, or problems with the gas valve closing intermittently.

Step-by-step fixes:

1. Confirm the gas supply by checking other appliances work normally.
2. Inspect and thaw the condensate pipe if frozen, following the gentle warming method outlined earlier.
3. Reset the boiler once after basic checks.
4. Run the heating at a moderate setting and listen for normal operation.
5. Recurring F29 needs professional attention from a Gas Safe engineer to investigate combustion settings and components.

For sensor faults, gas valve problems, or overheating, professional service is essential.

Upgrade Your Glow-Worm Boiler for Reliable Heating All Year Round

If your Glow-Worm boiler is repeatedly displaying error codes, it could be a sign that important components are wearing out. While some faults can be repaired, ongoing issues such as low pressure, ignition failures, flame loss, or pump problems often lead to increasing repair costs and the inconvenience of unexpected breakdowns.

At Eazy Heat, we make replacing your boiler simple and stress-free. We install high-efficiency new boilers for homeowners and landlords across the UK, with a straightforward online quotation process and professional installation from experienced engineers. Every installation is backed by a market-leading 12-year parts and labour warranty, giving you long-term peace of mind and dependable performance.

Use our online boiler quotation tool today to receive a clear, fixed-price quote in just a few simple steps. We’ll help you choose the right boiler for your property and arrange a fast, hassle-free installation, so you can enjoy efficient, reliable heating without the worry of recurring boiler error codes.

Frequently Asked Questions

How long do Glow-Worm boilers typically last before error codes become frequent?

Many Glow-Worm boilers provide good service for 10 to 15 years with annual maintenance. After this, components wear and faults increase.

Can frequent resetting damage my Glow-Worm boiler?

Occasional resets for minor issues are usually fine. Repeated resets without fixing the root cause can mask serious problems and should be avoided.

Are Glow-Worm boilers suitable for rental properties?

Yes, they offer decent reliability and parts availability. Regular servicing helps landlords meet safety requirements.

What should I prepare before an engineer visit for a Glow-Worm error code?

Note the exact code, when it appears, recent weather conditions, and any power issues. This helps speed up diagnosis.

Do Glow-Worm error codes relate to carbon monoxide safety?

Certain combustion or flue-related codes can. Always maintain a working carbon monoxide detector and seek professional help for relevant faults.