Scale and lime build-up

Heating water drives dissolved calcium and magnesium out of solution, and the crystals deposit on the hottest surfaces: heating elements on electric tanks, the burner-side metal on gas tanks, and the heat exchanger on tankless units. A scaled element or exchanger transfers heat poorly, which costs recovery, raises operating temperature, and eventually triggers overheat protection: Rinnai documents scale build-up as a cause of heat-exchanger overheat codes and a reason flushing is a warranty condition.

On gas tanks, sediment and scale at the bottom insulate the tank steel from the burner flame, which can overheat the bottom and shorten the tank's life; manufacturers' maintenance schedules call for periodic draining for exactly this reason.

Metro Vancouver's treated water is very soft, roughly 2 to 25 mg/L hardness depending on the source, which is far below the levels that produce rapid scale. For most homes supplied by Metro Vancouver water, the descaling interval can follow the manufacturer's minimum rather than the aggressive schedule hard-water regions need, and the anode and corrosion story matters more than scale.

The exceptions are real: homes with water softeners that blend, homes on private wells with hard groundwater, and tankless units that have run years without any flush. Scale already deposited does not dissolve on its own; it needs the manufacturer's flushing procedure or replacement.

Tankless units are flushed through their isolation valves with a manufacturer-approved solution, and electric tanks can have scale treated at the elements. Descaling chemicals and magnetic devices sold for scale removal vary widely in evidence; WaterHeating.ca recommends the manufacturer's documented procedure and does not endorse unverified products. Where supply hardness is the problem, treatment happens at the water, not just at the heater.