Two Weeks In: A New Glow-worm Owner’s Reality Check

The engineer has gone, the dust sheets are folded away, and your new Glow-worm is doing its thing. Then the questions start. Why does the radiator in the spare room feel cooler than the others? What’s that faint smell? Is the pressure gauge supposed to move? And is that white plume outside the flue a sign of trouble or just a cold November morning doing its thing?

The first two weeks after an installation are a settling-in period, not a pass-or-fail exam. A new boiler is a mechanical system finding its rhythm in your home, and your house is adjusting to it too. Some of what you notice is completely ordinary. A smaller number of things deserve a call back to the installer. The trick is knowing which is which before guesswork takes over.

The first 48 hours: smells, sounds and a bit of debris

A faint burning or oily smell in the first day or two is common. New components often have protective oils and manufacturing residues burning off, and the heat exchanger and pipework are warming up properly for the first time. Open a window, keep the rooms ventilated, and don’t panic. If the smell is strong, persists beyond a few days, or you smell gas, that’s different — gas smells mean calling the National Gas Emergency Service on 0800 111 999 straight away.

Noises are similar. Ticking as metal expands and contracts is normal. A bit of gurgling can be trapped air working its way through. A low hum from the pump or fan is part of normal operation. What you shouldn’t hear is repeated banging, kettling, or a loud vibration that travels through the house. Those are worth mentioning to your installer rather than living with.

Pressure watch: small movement is fine, constant dropping isn’t

Your Glow-worm’s pressure gauge will move a little. When the heating is off, it might sit around 1 to 1.5 bar. When the system heats up, it can rise. That’s normal expansion, not a fault.

What isn’t normal is pressure dropping below about 1 bar repeatedly, or finding the boiler has locked out because pressure has fallen. A one-off top-up after installation isn’t unusual while residual air works its way out, but if you’re topping up every few days, stop and call the installer. Constantly adding water can mask a leak and dilute the inhibitor that protects the system.

Radiators: uneven warmth is often a balancing act

A new boiler rarely means every radiator heats at exactly the same speed. Upstairs may lag behind downstairs. The radiator furthest from the boiler may take longer. A room with the TRV turned low will feel cooler by design. This is often about balancing rather than a boiler fault.

Give the system a few days, check the TRVs are set sensibly, and see whether the pattern settles. If one radiator stays cold at the bottom, cold at the top, or refuses to heat at all, note it down and call your installer. They can check for air, sludge, a stuck valve, or a balancing issue. Don’t start removing radiators or fiddling with valves yourself in the first fortnight.

The condensate plume: usually normal, sometimes worth a check

Modern condensing boilers, including Glow-worm models, produce a white plume from the flue when they’re working efficiently, especially in cold weather. It can look dramatic on a frosty morning, but it’s usually just water vapour condensing in the air.

The condensate pipe outside may drip too. That’s normal. What matters is that it isn’t blocked or frozen. If you hear gurgling from the boiler, notice water backing up, or the boiler locks out during a cold snap, the condensate pipe may need attention. In winter, a frozen condensate pipe is one of the more common reasons a boiler stops — and it’s usually a quick fix for an installer.

Noise: settling in versus complaining

A new boiler will make some noise. You may hear a whoosh when it fires, a gentle hum from the pump, or ticking as pipes warm up. These are ordinary.

Call your installer if you hear banging, kettling, loud grinding, or a noise that’s getting worse rather than settling. Also call if the boiler repeatedly locks out, shows an error code you don’t understand, or keeps firing and stopping in short bursts. A quick phone call now is better than a cold house in January.

The two-week checklist: when to call the installer back

Use this as a practical filter rather than a diagnosis.

• Call immediately: you smell gas, see water leaking from the boiler or pipework, or notice scorching or burning smells that don’t fade.
• Call within a day or two: pressure keeps dropping below 1 bar, the boiler locks out repeatedly, there’s no heating or hot water, or a radiator stays completely cold.
• Call if it persists: a gurgling or banging noise that doesn’t settle, a condensate pipe that seems blocked or frozen, or an error code that keeps returning.
• Mention it at the next service: a faint smell in the first 48 hours, a little ticking as pipes expand, or one radiator taking longer to warm up.

Don’t undo the good work

In the first fortnight, resist the urge to adjust every setting. Your installer will have commissioned the boiler for your home, and random knob-twiddling rarely improves things. Don’t box the boiler in, don’t block vents, and don’t add inhibitor yourself unless your installer tells you to. Keep the commissioning checklist and benchmark paperwork somewhere safe — it matters for your Glow-worm guarantee.

Most of what you notice in the first two weeks is the sound of a new system settling into a new home. A little smell, a little movement on the gauge, a radiator that needs balancing: these are ordinary. Genuine faults tend to be persistent, repeatable, and worth a phone call. Trust the checklist, keep a note of what you see, and let your installer do the diagnosing. That’s what the guarantee and the call-back are for.