A tankless unit that's losing hot water pressure over months rather than overnight in a Port Moody home usually points to scale accumulating inside the heat exchanger.
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Quick answer
Tankless scale buildup is mineral deposit that forms inside the heat exchanger every time the unit fires, gradually narrowing the internal passages and reducing how efficiently heat transfers to the water. It shows up as weaker flow, slower time-to-hot-water, and more frequent flow or temperature-limit shutdowns, and a professional descaling flush typically resolves it if caught before the exchanger is heavily narrowed.
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A tank-style water heater holds and reheats the same water slowly; a tankless unit heats fresh water on demand every single time a tap opens, which means the internal exchanger surfaces are exposed to far more heating cycles over a year. Dissolved minerals in the supply precipitate out onto those hot surfaces bit by bit, similar to the ring that forms in a kettle, except it's happening inside narrow copper or stainless passages rather than an open pot.
The consequence builds gradually. Flow tightens, the burner works harder to hit the target temperature rise, and the unit's internal sensors eventually flag a flow or temperature fault as the exchanger struggles to keep up.
Port Moody draws on the same Metro Vancouver reservoir supply as the rest of the region, which is comparatively soft water, so scale accumulates more slowly here than it would on a groundwater system. CANRO still sees it regularly in hillside homes around Heritage Mountain and older character properties near Moody Centre where the tankless unit has run for years without ever being flushed, particularly units tucked into tight mechanical closets that are easy to forget about.
| What's Found | Typical Path |
|---|---|
| Moderate scale, exchanger still flows reasonably | Standard descaling flush |
| Heavy, long-neglected buildup | Flush now, plan a follow-up flush within a year |
| Exchanger corroded or physically damaged from years of untreated scale | Heat exchanger or full unit replacement, tankless install ballpark $3,500–$7,500, not a quote |
Getting on a regular flush schedule is far less costly over time than letting scale run unchecked for a decade, and it's the single biggest factor in how long a tankless unit lasts.
Safety note
If you ever smell gas, notice soot around the burner compartment, or hear popping or rumbling from inside the unit, shut off the water heater if it's safe to reach and leave the home, then call FortisBC at 1-800-663-9911 from outside. Any work on the burner, gas valve, or venting of a tankless water heater must be done by a Technical Safety BC licensed gas fitter.
Scale-related flow loss tends to develop gradually over months and affects multiple fixtures, whereas a sudden drop at one tap is more likely a clogged aerator or a separate valve issue. A tech can confirm by checking flow directly at the unit.
No, Port Moody is on the same Metro Vancouver reservoir supply as most of the region, which is comparatively soft. Scale still forms over years of use because a tankless unit fires so frequently, just more slowly than it would on hard water.
It varies by unit and how much buildup has accumulated, but it's typically completed in a single visit alongside a general inspection of the unit.
Scale itself is a water-side performance problem, not a direct gas hazard, but a unit straining against restricted flow can behave erratically, so any accompanying gas or venting symptoms should always be checked by a licensed gas fitter.
The exchanger passages narrow further, flow keeps declining, and in more severe cases the metal itself can be damaged by the insulating effect of the scale, pushing the eventual fix from a flush toward a full replacement.
Yes, a clogged or neglected inlet screen filter restricts flow on its own and traps loosened scale during a flush, so cleaning or replacing it is a standard part of the service, not an optional extra.
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