Gas tankless installation sized for Metro Vancouver's winter, not the brochure

A tankless unit's capacity is a flow rate at a temperature rise, and in January the incoming water here can be below 8 °C, so the unit must lift it by about 40 °C to reach a 49 °C shower. That is why sizing starts with the fixtures that run at once and the manufacturer's flow-at-rise table, not the maximum GPM on the box. CANRO's assessment confirms whether one unit covers your peak, or whether two units or a buffer tank are the honest answer.

Installation is more involved than a tank swap: 2" PVC, CPVC or polypropylene venting to an exterior wall within the manufacturer's equivalent-length limit, a gas supply able to carry up to 199,000 BTU/h, a condensate drain with a neutralizer where required, a 120 V receptacle, and isolation valves for the annual flush. CANRO states on its own site that tankless installations usually take one to three business days.