BoilerBuddy · symptom hub
Pick what's happening with your boiler.
The boiler is doing something it shouldn't, and you want to know what it means before picking up the phone. The cards below bring together seventeen everyday boiler symptoms and heating guides — each with a one-line plain-English summary, the safe-at-home check, and a clean line for when it's time to call a Gas Safe engineer. Pick the card that matches what your boiler is doing; the per-symptom guide takes it from there.
17 everyday symptoms — pick the one that matches what your boiler is doing.
Start with the common ones
The boiler symptom guides people reach for first.
If you need a quick starting point, these four guides cover the symptoms homeowners ask about most often — with the safe checks and clear next step in one place.
Boiler keeps losing pressure
The visible pressure reading falls again after it has been checked. Record what you see and use your exact model manual before taking any action.
Read the Boiler keeps losing pressure guideNo hot water from the boiler
The boiler runs, but the taps are not giving you hot water. Start with the controls and display, then use the guide to choose a safe next step.
Read the No hot water from the boiler guideRadiators not heating
Radiators that stay cold across the whole system, or a single cold one while the rest heat — usually a TRV stuck, an air-lock, magnetite sludge, or a jammed diverter. Plain-English triage, the bleed vs sludge call, and the line for when to call a Gas Safe engineer.
Read the Radiators not heating guideBoiler banging or kettling
A rumbling or kettle-like sound may have more than one explanation. Note when it happens and follow the guide for safe next steps.
Read the Boiler banging or kettling guideSeventeen everyday guides
Pick the symptom that matches your boiler — we'll keep it calm and honest.
Seventeen symptom guides, each one a quiet, single-page explanation you can read in two minutes.
All seventeen symptom guides
Search symptoms
17 guides shown
Boiler not igniting
The boiler appears to respond to a heat demand but does not start or stay alight. Record any displayed code and leave internal checks to an engineer.
No hot water from the boiler
The boiler runs, but the taps are not giving you hot water. Start with the controls and display, then use the guide to choose a safe next step.
No hot water but heating works
The radiators warm up but the hot tap stays cold. This pattern can have several explanations; note what the boiler and controls show.
Boiler keeps losing pressure
The visible pressure reading falls again after it has been checked. Record what you see and use your exact model manual before taking any action.
Boiler banging or kettling
A rumbling or kettle-like sound may have more than one explanation. Note when it happens and follow the guide for safe next steps.
Boiler leaking water
Water is visible around or beneath the boiler. Keep clear of wet electrical areas, note where the water appears, and arrange professional help.
Boiler won't turn on
There is no visible response when heat or hot water is requested. Check external controls and the display without opening the boiler case.
Boiler keeps cutting out
The boiler starts and then stops, sometimes showing a code. Note the timing and display; normal control cycling and a repeated fault can look different.
Boiler keeps turning off
Boiler fires for a few minutes then stops with a flashing code or a quiet cut-off — usually a low-pressure lockout, thermostat shutdown, overheat trip, frozen condensate, or a flame-loss interlock. Safe-at-home checks and the line for when to call a Gas Safe engineer.
Boiler leaking
Sealed-combii leakage on the most-likely path — pressure-relief discharge, a weeping pump seal, or a corroding heat exchanger. Tell-tale signs and the line for when to call a Gas Safe engineer.
Boiler showing a fault code
The display is showing letters or numbers you do not recognise — record it exactly, search the fault-code directory, and stop before repeated resets or unsafe checks.
Radiators not heating
Radiators that stay cold across the whole system, or a single cold one while the rest heat — usually a TRV stuck, an air-lock, magnetite sludge, or a jammed diverter. Plain-English triage, the bleed vs sludge call, and the line for when to call a Gas Safe engineer.
Cold spots on radiators
Notice whether the cold area is at the top, bottom, or spread across the radiator. The pattern is useful information, but it does not confirm a cause.
No heating from boiler
The boiler is firing but no heat reaches the radiators — usually the thermostat, an air-lock, a faulty diverter, or low system pressure. Plain-English triage and the safe-at-home checks, with the clear line for when to stop and call a Gas Safe engineer.
Boiler making strange noises
Rumbling, banging, gurgling, humming or whistling can have different explanations. Note the sound and when it happens, then follow the safe guide.
Boiler losing pressure
A falling gauge reading can have several explanations. Check it only as described in your exact boiler manual; repeated loss needs a Gas Safe engineer.
Cold radiator at the bottom
One radiator cold at the bottom while the others heat fine — usually trapped air or magnetite sludge. A guided walkthrough on the bleed vs sludge call, with the line for when it's an engineer.
Stuck somewhere else?
Four related hubs you may have landed on instead.
If a code is showing
Boiler error codes
If the display on the front of the boiler is showing a code rather than a behaviour — typed-codes lookup for Worcester Bosch, Vaillant, Baxi, Ideal, Viessmann and Glow-worm.
Open guide →If you can smell gas
Gas-leak safety
Stop, open doors and windows, dial 0800 111 999 from outside. The single-page, no-panic guide for the moment a smell of gas hits you.
Open guide →If a CO alarm is sounding
Carbon monoxide safety
Yellow-flame guidance, CO poisoning symptoms, and the exact NHS-aligned line for when to call 111 or 999. The single-page, stop-and-think guide for the CO-alarm moment.
Open guide →If you can smell gas right now
Smell of gas — what to do
STOP. Open doors and windows. Leave the property. Call 0800 111 999 from outside. The single-page, no-panic guide for the moment a gas smell hits you.
Open guide →When the right next step is a registered engineer
Find a Gas Safe engineer
The public HSE register, postcode search and the per-symptom handover PDF — the calm hand-off when triage has flagged territory a registered engineer should handle.
Open guide →Guidance only — when in doubt, a registered Gas Safe engineer makes the final call. BoilerBuddy is not affiliated with any boiler manufacturer.