Error codes
Modern tankless units show fault codes for ignition, flow, flame, exhaust or venting issues. We translate them and diagnose the underlying cause.
Water Heaters / Tankless Water Heater Repair
Tankless Water Heater RepairCareful diagnostics and dependable repairs for tankless water heaters — from ignition faults to scale buildup and flow issues.
— Common Tankless Problems
Symptoms we diagnose across GTA homes.
Tankless water heaters are excellent when they're set up and maintained properly — but they don't tolerate skipped maintenance well. These are the issues we're most often called out to.
No hot water
Unit powers up but never fires, or fires briefly and shuts down. Often ignition, gas supply, exhaust or safety-related.
Scale buildup
Minerals in Toronto water quietly coat the heat exchanger over time, hurting output and eventually triggering error codes.
Flow issues
Weak flow, cold-water sandwich or unit not activating at low flow rates — often a flow sensor, filter screen or plumbing-side issue.
Ignition
Failed ignitor, weak gas supply, flame-sensor or venting-related lockouts that need proper diagnostics rather than a reset.
Venting & exhaust
Exhaust or intake blockages, condensate drain issues or venting problems that trigger safety shutdowns.
Temperature fluctuation
Hot then cold then hot again — often minimum-flow, mixing-valve or recirculation-related, sometimes a scale problem.
Unusual noises
Rattles, buzzing or vibration that appears after years of use — worth inspecting rather than ignoring.
Missed maintenance
Many tankless problems trace back to skipped descaling. We can resolve the immediate issue and reset a proper maintenance cadence.
— Our Diagnostic Process
Diagnosed properly, before it's repaired.
Tankless units are more complex than tank heaters. Every service call follows a consistent process so nothing is missed.
- 01
Inspection
Careful visual review of the unit, gas supply, venting, condensate drain and plumbing connections.
- 02
Error-code review
Fault history read from the control board and interpreted — not just cleared.
- 03
Testing
Gas pressure, flow rates, exhaust behaviour and flame signal measured under real running conditions.
- 04
Diagnosis & options
Plain-language explanation of what's happening, with honest repair options and their trade-offs.
- 05
Transparent pricing
Written pricing before any work begins — including descaling if it's part of the fix.
- 06
Verification after repair
Hot-water delivery, temperature and error-code status confirmed before we leave.
— Why Homeowners Choose Proper HVAC
Water heater work done properly.
Water-heater-literate technicians
Comfortable with tank and tankless systems — gas, electric and power-vent — from major manufacturers.
Clear communication
Plain-language explanations of what's happening and what to do next.
Careful workmanship
Clean installs, tidy work and a proper check before we leave.
Respect for your home
Boot covers, drop cloths and thoughtful protection of your finishes.
Repair-first philosophy
We fix what can be fixed and only recommend replacement when it's genuinely the better choice.
Honest recommendations
The work your water heater actually needs — nothing added, nothing exaggerated.
— FAQ
Frequently asked questions.
What Toronto homeowners ask us most often about tankless water heater repairs.
Still not sure? Contact us and we'll help you decide the right next step.
Codes vary by manufacturer, but they generally point to ignition, flame, flow, exhaust, temperature or venting issues. We interpret the code, identify the root cause and correct it — not just clear the fault.
Common causes include gas supply issues, ignition faults, flow-sensor problems, blocked exhaust or intake, or scale buildup restricting the heat exchanger. A proper diagnostic tells us which.
Minerals in the water gradually coat the inside of the heat exchanger. That reduces heat transfer, causes error codes and eventually damages the exchanger. Regular descaling is the single most important thing you can do for a tankless unit.
Common causes include running below the unit's minimum flow rate, mixing valves needing adjustment, recirculation issues or scale buildup. Fluctuation isn't always a fault — sometimes it's a setup issue.
Some homeowners do. Proper descaling requires isolation valves, a pump, the right descaling solution and enough time to circulate. We handle it as part of maintenance so it's done right.
Annually is a good baseline in most of the GTA, more often in harder-water areas. Skipping descaling is the most common reason tankless units start throwing codes.
Usually yes — tankless units are engineered to be serviced. A failing tankless in the first 10–15 years is almost always worth repairing rather than replacing.
Yes. We service tankless water heaters from major manufacturers, natural-gas and propane, condensing and non-condensing.
Proper HVAC provides tankless water heater repair for homeowners throughout Toronto and the Greater Toronto Area, including Etobicoke, North York, Scarborough, York, Vaughan, Richmond Hill, Markham, Mississauga, Oakville and Brampton.
— Get Started
Tankless Not Working?
Book a service visit, ask about descaling as part of ongoing maintenance, or join ProperCare for peace of mind.
Or call 416-580-HEAT (4328)