Glow-worm boiler fault codes can indicate anything from a temporary pressure issue to a fault affecting ignition, circulation or the boiler’s controls. They do not automatically mean you need a new boiler, but repeated codes on an older appliance can be a sensible point to compare replacement options.
Quick answer: check the exact code against the manual for your specific Glow-worm model, and do not keep resetting a boiler that repeatedly locks out. If it is old, unreliable or facing uncertain repair costs, a new boiler quote can give you a clearer long-term decision. Get a fixed boiler quote online.
What Glow-worm boiler fault codes tell you
A fault code is the boiler’s way of stopping operation when it detects a condition that may prevent safe, effective heating or hot water. The letters and numbers shown on the display are useful information, but their exact meaning can vary between Glow-worm ranges and generations. Always use the instructions supplied with your model rather than relying on a code list intended for a different boiler.
Some codes relate to straightforward operating conditions, such as low system pressure. Others can point to an issue with the ignition process, fan, pump, sensors or printed circuit board. A code alone does not confirm which part is at fault or whether a repair is worthwhile.
If you smell gas, suspect a gas leak or feel unwell with symptoms that could be linked to carbon monoxide, leave the property if necessary and call the National Gas Emergency Service on 0800 111 999. Do not operate electrical switches or attempt to investigate the appliance. For any boiler fault, work must be assessed by a suitably qualified Gas Safe registered engineer.
Common Glow-worm boiler fault codes
The following examples are commonly seen across various Glow-worm models, but wording and applicability differ by appliance. They are useful for understanding the type of problem, not for diagnosing or fixing the boiler yourself.
- F.22 is commonly associated with low water pressure or a lack of water in the heating system. A pressure reading that drops repeatedly may indicate a wider issue rather than a one-off top-up requirement.
- F.28 generally relates to an unsuccessful ignition attempt. The boiler has tried to light but has not established a flame.
- F.29 commonly indicates flame loss during operation. This can be intermittent and may leave you without heating or hot water.
- F.75 on certain models can relate to pressure changes not being detected when the pump operates. It may involve the pump, pressure sensor or circulation within the system.
Codes beginning with other letters, including S codes, can sometimes be status messages rather than faults. The key point is whether the boiler continues to work normally, locks out, or needs regular resets. Photograph the display and note when the code appears. This gives an engineer or an installation surveyor more useful context.
When a fault code is a replacement warning
A single fault on a newer boiler with a known cause may not justify replacement. The decision changes where failures recur, parts are costly or difficult to source, or the boiler has become disruptive to live with.
Age matters, but it is not the only factor. A ten-year-old boiler that has been dependable may still have useful life left. Conversely, a younger boiler with repeated lockouts and an unsuitable output for the property can be frustrating and expensive. Landlords may also need to consider the impact of an unreliable boiler on tenants, particularly during colder months.
It is usually worth comparing replacement options when the boiler has recurring ignition or circulation problems, needs repeated visits, has a significant repair estimate, or no longer meets the household’s hot-water demand. A replacement can also make sense if you are planning a kitchen alteration, moving the boiler, replacing a back boiler or changing from a regular boiler to a combi system.
Repair cost versus a new boiler price
There is no universal rule that a repair above a certain amount means replacement is right. The useful comparison is the total likely cost over the next few years against the cost, warranty and reliability of a new installation.
As a broad UK guide, a straightforward like-for-like combi boiler replacement often falls in the region of £2,000 to £4,500, including the boiler and installation. More involved work can cost more. For example, changing boiler type, moving the appliance, updating flue routes, fitting a new cylinder, or replacing unsuitable controls can increase the price.
These are estimates, not fixed prices. A confirmed quote should account for the property, chosen boiler, existing system, access and installation requirements. It should also make clear what is included, such as the boiler, flue components, controls, system cleaning where required, commissioning and removal of the old appliance, as well as any work that may cost extra.
A fixed online quotation is most useful when the property details are accurate. Smart Adapt checks postcode availability, installation requirements and the information provided before a quote or installation is accepted. Boilers are installed by Gas Safe registered engineers, with any manufacturer warranty subject to the selected product, correct installation, registration and the manufacturer’s current terms.
Choose the replacement around your home, not the old boiler
A fault code is often the trigger for a decision, but it should not dictate the replacement boiler. The right choice depends on the number of bathrooms, how many people use hot water at the same time, radiator demand, available space and the existing heating system.
Combi boilers
A combi boiler provides heating and hot water directly from the mains, without a separate hot-water cylinder. It is often a practical option for flats and smaller to medium-sized homes with one bathroom and adequate incoming mains water pressure and flow.
The trade-off is that hot-water performance is limited by the boiler’s flow rate and the mains supply. If two showers are likely to run together, a standard combi may not be the right fit even if the existing boiler is one.
System boilers
A system boiler works with an unvented or vented hot-water cylinder. It can better suit homes with more than one bathroom or a higher demand for simultaneous hot water. It requires space for a cylinder, but can offer a more comfortable solution for busy households.
Regular boilers
Regular, or heat-only, boilers are normally connected to a cylinder and may use tanks in the loft. Keeping this arrangement can be sensible where the existing system is suitable and the home needs stored hot water. Converting to another boiler type is possible in many properties, but the additional pipework, cylinder changes and alterations should be priced properly before you decide.
What can affect the final installation price
A boiler code does not reveal the full installation scope. Before committing to a replacement, check that the quotation reflects the work your home genuinely needs. The main cost variables are the boiler output and model, boiler type, flue position and length, condition of the heating system, controls, access, and whether the boiler stays in the same location.
Extra work is more likely with a back-boiler replacement, a move from a cupboard to another room, a conversion from regular to combi, or where new pipework and a condensate route are required. Older systems may also need cleaning or component changes to protect the new boiler. These are not necessarily problems, but they should be explained before installation rather than appearing as a surprise on the day.
Installation time also depends on the scope. A straightforward replacement can often be completed in a day, while a conversion, relocation or more complex system update may take longer. A professional quote should set realistic expectations for access, disruption and any time without heating or hot water.
Frequently asked questions
Can I reset a Glow-worm boiler after a fault code?
Follow the model-specific instructions once if appropriate, but do not repeatedly reset a boiler that keeps locking out. Frequent resets can mask an underlying issue and do not establish that the appliance is safe to use.
Does F.22 mean I need a new boiler?
Not necessarily. F.22 is commonly linked to low pressure, but recurring pressure loss on an older boiler or system is a reason to assess the overall condition and likely future costs.
Are Glow-worm fault codes the same on every model?
No. Meanings can differ between ranges, so use your boiler’s manual and record the exact code shown. The model name is usually shown on the appliance casing or paperwork.
How do I know whether a combi boiler is suitable?
Consider your mains water supply, bathroom number and whether people need hot water at the same time. A quote should assess hot-water demand rather than simply replacing like for like.
Will a new boiler come with a warranty?
Most new boilers have a manufacturer warranty, but the length and conditions vary by model. Ask for the warranty terms for the exact boiler quoted, including registration and installation requirements.
Can I spread the cost of a replacement boiler?
Finance may be available on selected installations, subject to status, eligibility and lender approval. Check the term, monthly payment, total amount payable and representative information before choosing finance.
Get clarity before the next lockout
A repeated Glow-worm code is inconvenient, especially when heating or hot water is already unreliable. Rather than choosing under pressure after another breakdown, compare a suitably sized combi, system or regular boiler against the realistic cost and uncertainty of keeping the old appliance running.
Get a fixed boiler quote online. A clear quote should help you see the boiler options, included work, possible extras and next steps before you make a decision.