Hard water is water carrying dissolved minerals, mainly calcium and magnesium, that drop out as scale when the water is heated. In a tank water heater, scale settles on the bottom between burner and water, so the burner runs longer. In a tankless unit, it coats heat exchanger passages and restricts flow, costing efficiency first and lifespan second.
Why it matters to you
Water hardness varies by supply across the Lower Mainland and Fraser Valley, so it is worth checking rather than assuming; in the harder-water pockets of the valley, descaling a tankless unit is not optional maintenance.
Practical guidance
Watch for popping or rumbling from the tank, hot water running out sooner, longer recovery, or tankless error codes. Flush a tank and descale a tankless unit annually, and if you lower the thermostat to slow scaling, keep it at or above 60°C to limit Legionella risk.