Gas Boiler Troubleshooting Guide
Common boiler problems in plain English — likely causes, the safe checks you can make yourself, and exactly when to call a licensed BC gas technician.
Safety first. If you smell gas, hear a CO alarm, or feel dizzy or nauseous near the boiler — leave the building immediately and call 911 or FortisBC at 1-800-663-9911 from outside. Then call us at 604-359-1081 once the area is safe. Never attempt gas work yourself — in BC it must be done by a licensed gas fitter.
Some boiler issues have safe checks any homeowner can make. Others need a licensed gas technician on the first call. Use this guide to tell which is which — then choose your brand below for a fault-code-specific walkthrough, or call us with confidence when you need help.
Troubleshoot by your boiler brand
Brand-specific guides map your symptom to that manufacturer's real fault codes and the safe checks that apply.
Common boiler problems & what they mean
No heat at all
medium severity
Common causes
- Thermostat batteries dead or thermostat not calling for heat
- Boiler in lockout (error code on display)
- Power tripped at breaker
- Gas supply off (knock-out, FortisBC outage, propane tank empty)
- Pressure too low (< 12 psi cold)
- Pump seized or air bound
Safe checks you can make
- Set thermostat 5°F above room temp and listen for boiler activation
- Check breaker — flip fully off then on
- Check pressure gauge — should be 12-15 psi cold
- Check display for any error codes (look them up on our error-codes pages)
- Look for gas valve handle in the ON position (handle in line with the pipe)
When to call us
If the thermostat is calling and there's no response, no error code, and power+gas+pressure are all OK — call us. Likely circulator pump, gas valve, or control board.
Boiler ignites but won't stay on (short-cycling)
medium severity
Common causes
- Oversized boiler for the load (chronic issue)
- Dirty flame sensor (very common)
- Low gas pressure
- Stuck or undersized circulator pump
- Dirty heat exchanger
- Failing outdoor reset sensor
Safe checks you can make
- Note how long it runs before shutting off — under 5 minutes is too short
- Check that thermostat differential isn't set too tight (typical: 1-2°F)
When to call us
Short-cycling damages a boiler over time and wastes gas. Most cases need a tech to clean the flame sensor, measure gas pressure, and check the outdoor reset curve.
Water leaking from the boiler
high severity
Common causes
- Pressure relief valve discharging (system overpressure)
- Condensate drain leak (very common on condensing units)
- Heat exchanger leak (serious — usually means replacement)
- Pipe fitting or pump seal leak
- Expansion tank failure causing overpressure
Safe checks you can make
- Identify where the water is coming from — top, bottom, or side of the unit
- Check pressure — if above 30 psi, expansion tank may be bad
- Check the PRV (pressure relief valve) discharge tube
- Place a pan to contain water until a tech arrives
When to call us
Always call. Water leaking onto live electrical components or onto a hot heat exchanger is dangerous. We'll determine if it's a serviceable seal/valve or a more serious issue.
Boiler making strange noises
medium severity
Common causes
- Kettling — limescale buildup or low flow causing localized boiling
- Banging on startup — gas valve issue or air in the system
- Whistling — high flow through restricted passage (scale or trapped air)
- Humming/buzzing — failing circulator pump
- Rumbling — failing combustion fan or air starvation
Safe checks you can make
- Note the type of sound and when it happens (startup, mid-cycle, shutdown)
- Check pressure and bleed radiators if you have them
When to call us
Most boiler noises are early warnings — addressing them early often prevents major repairs later. Call us before the noise gets worse.
Pressure keeps dropping
medium severity
Common causes
- Leak somewhere in the system (often hidden in walls or floors)
- Bad pressure relief valve discharging slowly
- Bleeder valves left slightly open
- Expansion tank waterlogged
- Condensate trap blockage causing pressure swings
Safe checks you can make
- Top up to 12-15 psi cold (most boilers have a feed valve)
- Look for visible water at radiators, baseboards, pipes, valves
- Watch the gauge for the next few hours — fast drop indicates active leak
When to call us
Repeatedly needing to top up means there's a leak. We use moisture detection and pressure isolation testing to locate hidden leaks.
Boiler smells (gas, sulfur, hot electrical)
high severity
Common causes
- Gas leak (mercaptan rotten-egg smell)
- Burning dust on first startup of the season (normal, clears in 15-30 mins)
- Failing electrical component (hot plastic/electrical smell)
- Sulfur water reacting with anode in connected water heater
Safe checks you can make
- Gas smell — LEAVE the building, call 911 or FortisBC 1-800-663-9911 from outside
- Hot electrical smell — turn off power at the breaker if safe to do so
When to call us
Any persistent unusual smell warrants an immediate service call. Don't try to diagnose a gas smell yourself.
Still stuck?
Call our Burnaby office during business hours and describe what's happening. Many issues can be diagnosed over the phone — and most repair appointments are available same-day.
604-359-1081Boiler troubleshooting — FAQ
What should I check before calling about a boiler problem?
A handful of checks are safe for any homeowner: confirm the thermostat is calling for heat (and replace its batteries), check the breaker, read the pressure gauge (12–15 psi cold is normal), look for any error code on the display, and confirm the gas isolation valve is open. Anything beyond that — the gas valve, burner, combustion or safety controls — is licensed gas work in BC and should be left to a TSBC-certified technician.
Is it safe to keep resetting a boiler that keeps shutting down?
Reset once. If the boiler locks out again, stop. Repeated resets on ignition, flame, gas or venting faults can be genuinely dangerous and can damage the heat exchanger. A recurring lockout means a safety circuit is doing its job — switch the boiler off and call GasBoilers.ca at 604-359-1081 for a licensed diagnosis.
Do you troubleshoot every boiler brand in Greater Vancouver?
Yes. Our Red Seal–certified, TSBC gas-licensed technicians service every major brand — Navien, IBC, Viessmann, Rinnai, Bosch, Noritz, Weil-McLain, Lochinvar, Baxi and more — across Vancouver, Burnaby, Surrey, Richmond, the Tri-Cities and the rest of Greater Vancouver, with same-day appointments often available.
Error codes by brand
Skip the guesswork — get a licensed diagnosis.
Red Seal–certified gas technicians across Greater Vancouver. Upfront pricing, same-day service available.