Even on White Rock's relatively soft municipal water, mineral scale accumulates inside a tankless heat exchanger year after year, and it's one of the most preventable causes of reduced performance.
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Quick answer
Scale buildup inside a natural-gas tankless water heater's heat exchanger narrows internal passages over time, showing up as reduced hot water flow, longer wait times for hot water, popping or ticking sounds during operation, and occasional temperature swings. Even on relatively soft municipal water, scale accumulates gradually, and the standard fix is a descaling flush performed with a pump and a mild descaling solution rather than replacement.
Need a licensed gas fitter for your tankless water heater? Call CANRO at (604) 359-1081 — residential natural-gas heating and hot water across Metro Vancouver since 1999.
White Rock draws its municipal water through the regional system, which is comparatively soft next to groundwater or well sources found further out in the Fraser Valley, but soft is not the same as mineral-free. Every time water is heated, dissolved minerals in it, mostly calcium and magnesium, become less soluble and some precipitate out onto the hottest surfaces inside the unit, which is the heat exchanger. Over years of regular use, that mineral layer thickens and begins to insulate the heat exchanger from the water flowing past it, forcing the burner to work harder to reach the same output temperature.
Homes with a tankless unit installed for more than three or four years without any descaling maintenance are the ones CANRO most often finds with measurable scale, regardless of which part of Metro Vancouver they're in.
A technician isolates the unit using its service valves, connects a pump that circulates a mild descaling solution through the heat exchanger in a closed loop for a set period, then flushes it thoroughly with clean water before returning the unit to normal operation. It's a routine, non-invasive process that doesn't require draining your home's plumbing or disconnecting the unit from the gas or vent lines.
| Maintenance history | Recommended action |
|---|---|
| Never descaled, unit over 2 years old | Descaling flush recommended at next service |
| Descaled within the last 12-18 months | Continue on annual schedule |
| Symptoms present (noise, reduced flow) | Descale promptly, then reassess schedule |
Left long enough, heavy scale buildup forces the unit to run hotter and longer to compensate, which accelerates wear on the heat exchanger and other components, and in more advanced cases can contribute to premature heat exchanger failure. It rarely causes a sudden breakdown on its own, but it steadily shortens the unit's comfortable service life.
Scale buildup, even when significant, is addressed with descaling rather than replacement in the large majority of cases. Replacement becomes the more sensible option only when scale has been left unaddressed for many years alongside other age-related wear on an older unit.
Safety note
If at any point you smell gas, hear hissing near a gas line or fitting, or a carbon monoxide alarm sounds, leave the home immediately and call FortisBC's emergency line at 1-800-663-9911 from outside. Do not attempt to relight, reset, or investigate the appliance yourself.
Roughly annually is a common recommendation for Metro Vancouver homes on municipal water, though your technician can tailor a schedule to your household's actual hot water usage.
Some homeowners with the right pump kit do attempt it, but CANRO recommends a licensed technician handle it, since it's also an opportunity to inspect the venting, gas connections, and other components at the same time.
Manufacturer warranty terms vary, and some require documented maintenance including descaling; verify your certificate for your specific model's requirements.
Most homeowners notice improved flow and quieter operation right after a flush, though very advanced buildup may only partially reverse.
It's the most common cause, but a technician will confirm during inspection rather than assuming, since other issues can occasionally produce similar sounds.
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