Many tankless warranties are conditional on regular descaling, and without dated service records a manufacturer can deny an otherwise valid claim.
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Quick answer
Most tankless gas water heater warranties include a maintenance clause requiring periodic descaling of the internal heat exchanger, and manufacturers can deny a warranty claim if the homeowner cannot produce records showing this maintenance was performed on the recommended schedule. Because tankless units run water through a compact heat exchanger at high temperatures, mineral scale builds up faster relative to the exchanger's small internal passages than it would in a large storage tank. Keeping dated invoices or service logs from every descaling visit is the single most important piece of paperwork a tankless owner can maintain for warranty purposes.
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A tankless water heater heats water on demand as it passes through a compact heat exchanger, rather than storing a large volume of preheated water the way a conventional tank does. That compactness is part of what makes tankless units space-efficient and able to deliver continuous hot water, but it also means the internal passages the water travels through are narrow and heavily loaded with heat. Mineral scale that would spread out relatively harmlessly across the bottom of a large storage tank instead concentrates inside a tankless unit's exchanger passages, where it insulates the metal from the water and forces the burner to work harder to reach the same output temperature.
Metro Vancouver's municipal water is generally on the softer side because it comes from protected mountain reservoirs rather than groundwater, which is a genuine advantage for tankless equipment compared to many other regions. Homes on well water, more common in parts of the Fraser Valley, tend to see harder water and correspondingly faster scale buildup, which is one reason manufacturers do not set a single descaling interval that fits every property equally.
Because scale buildup is a maintenance issue rather than a manufacturing defect, tankless manufacturers commonly write their warranty terms to require periodic descaling as a condition of coverage remaining valid. If a unit's heat exchanger fails prematurely and an inspection finds heavy, long-term scale buildup with no service history to show it was ever addressed, the manufacturer has grounds to treat the failure as a maintenance neglect issue rather than a covered defect, and deny the claim.
This is different from most storage tank warranties, which rarely specify a maintenance schedule as a strict condition of coverage. Tankless warranty language is more likely to spell out an expected descaling interval and to ask for proof of service at claim time, precisely because the failure mode is so closely tied to water quality and maintenance discipline rather than random component defects.
A proper descaling service circulates a mild acidic cleaning solution through the unit's heat exchanger using isolation valves and a small pump, dissolving mineral deposits from the internal passages without disassembling the unit. Most tankless installations include dedicated service valves specifically for this purpose, installed at the time of the original setup. If your unit does not have these valves, a technician can typically add them, which makes future descaling faster and less invasive.
A thorough visit also includes flushing the inlet water filter (if equipped), inspecting the venting for any signs of deterioration, and checking combustion performance, since a unit fighting scale buildup often shows subtly different burner behaviour even before an outright fault occurs.
Any of these signs are worth a service call sooner rather than later, since catching scale buildup early is both cheaper to address and better for preserving the unit's warranty standing than waiting until a component fails outright.
Safety note
A descaling service involves circulating a cleaning solution through gas-fired equipment and its venting connections, and should only be performed by a Technical Safety BC licensed gas fitter who understands the unit's isolation valves and venting system. If you ever smell gas near the unit, leave the home and call FortisBC at 1-800-663-9911.
This depends on your local water hardness and the manufacturer's specific guidance for your model, so check your unit's documentation rather than assuming a single interval applies everywhere. Homes on harder well water, more common in parts of the Fraser Valley, generally need more frequent descaling than homes on Metro Vancouver's softer municipal supply.
Scale buildup can reduce efficiency, cause error codes, and eventually contribute to a heat exchanger failure, and if that happens the manufacturer may deny a warranty claim citing lack of maintenance. Keeping dated service records is the best protection against this outcome.
Most tankless installations include isolation service valves specifically for descaling, installed at the time of the original setup. If yours does not have them, a licensed technician can typically add them during a service visit.
Generally no — most warranty claim processes ask for dated invoices or service records as proof, not just a verbal confirmation. This is why keeping every descaling receipt from day one matters.
No. Metro Vancouver's municipal water is comparatively soft, which slows scale buildup compared to harder water sources, but it does not eliminate it, and manufacturers still expect some periodic descaling on the schedule specified for your model.
Often yes, if scale buildup is the cause, though a technician should confirm that diagnosis rather than assuming, since flow and temperature symptoms can also point to a failing flow sensor or valve. A proper diagnostic visit rules out other causes before or alongside a descaling service.
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