How to Repressurise a Glow-Worm Boiler: Easy Step-By-Step Guide
Repressurising your Glow-worm boiler restores proper water levels in the heating system, getting your radiators warm and hot water flowing again without hassle.
Most UK homeowners and landlords handle this quick job themselves when the pressure gauge drops below 1 bar or an error like F22 appears on the display, it’s a common fix that keeps everything running smoothly.
How to Repressurise a Glow-worm Boiler: Step by Step
Repressurising your Glow-worm boiler follows a simple, safe process that takes just a few minutes once you’re set up.
- Turn off your boiler at the control panel and let the system cool completely (at least 30–60 minutes) to get an accurate cold reading.
- Find the filling loop underneath the boiler – it’s usually a silver hose with two valves.
- Slowly open both valves (turn them 90 degrees or to the open position; some need a flathead screwdriver if they’re stiff). You should hear water flowing gently into the system.
- Watch the pressure gauge closely – add water until it reaches 1.2–1.5 bar (never go over 1.5–2 bar to avoid over-pressurising).
- Close both valves tightly in the reverse order (often close the mains side first, then the system side) to stop the flow.
- Reset the boiler if needed (press the reset button or switch it off/on) and check the pressure holds steady over the next day.
If your model has a green locking collar or push-up disconnector (common on Ultracom²), push it up and lock it before opening the taps.
What Pressure Should My Glow Worm Boiler Be At?
Your Glow-worm boiler should sit at 1 to 1.5 bar on the gauge when cold for best performance and efficiency. This range ensures good circulation without straining components. Aim for around 1.2–1.3 bar after repressurising to give a little buffer.
If it climbs above 2 bar, carefully bleed a radiator to release excess water and bring it down.
How Do I Locate the Filling Loop on My Glow Worm Boiler?
The filling loop on your Glow Worm boiler is typically a flexible silver braided hose with two valves underneath the unit, connecting the cold mains water to your heating system. Many modern models like Energy, Ultracom, Flexicom, or Ultimate have a built-in or integral filling loop right there for easy access.
Older models might use a detachable external hose (sometimes stored nearby) or a key system – check your user manual if it’s not obvious. Look for two small blue or black handles/levers; one often connects to the mains inlet and the other to the system return.
What If Pressure Keeps Dropping After Repressurising?
If pressure keeps dropping after repressurising your Glow-worm boiler, there’s likely a small leak somewhere in the system, perhaps at a radiator valve, pipe joint, or even inside the boiler. Never keep topping up repeatedly without finding the cause, as it can lead to bigger issues like corrosion or component damage.
A professional inspection spots hidden leaks early and prevents costly repairs down the line.
If you’re noticing repeated pressure drops or other odd behaviour, a professional boiler service can diagnose and resolve it before it becomes a costly breakdown.
How to Prevent Low Pressure Problems in Your Glow-worm Boiler?
You can prevent low pressure problems in your Glow-worm boiler by checking the gauge monthly, bleeding radiators only when needed, and keeping an eye out for damp patches around pipes or the unit. Annual servicing catches wear on parts like valves or the expansion vessel before they cause drops.
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If you’re due for a routine check-up, tune-up, or want to prevent future issues, start with our boiler service plans.
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Frequently Asked Questions
Is it safe to repressurise my Glow Worm boiler if I hear unusual noises while filling?
Stop immediately if you hear banging or rushing sounds beyond normal water flow – this could indicate air pockets or a fault. Bleed radiators first or call a Gas Safe engineer to check safely.
Do all Glow Worm models use the same repressurising method?
Most combi models like Energy, Flexicom, and Ultracom share similar built-in loops, but older system or regular boilers might need an external hose or key. Always refer to your specific model’s manual for exact details.
What happens if I over-pressurise my Glow Worm boiler above 2 bar?
The pressure relief valve usually opens to release excess water (you might see a small drip outside), but repeated over-filling stresses components. Bleed a radiator to drop it back to 1–1.5 bar quickly.
How often should I check the pressure on my Glow Worm boiler?
Check monthly, especially after bleeding radiators or in cold weather when systems work harder. Regular monitoring catches drops early and avoids lockouts.
Will repressurising fix other Glow Worm boiler faults like no hot water?
It often helps if low pressure is the cause, but if hot water stays cold after reaching correct pressure, another issue like a diverter valve might be at play – best checked during a service visit.
