For our luxury line, we have the 931 series which can provide endless hot water for up to 4+ showers. And with its Quick-Connect system, two units can be linked together to meet the high demand of today’s luxury homes. To accommodate the higher flow rate demand, these units have a dual flame burner, a redesigned heat exchanger and 25% thicker copper piping. No other tankless water heater in its class can beat its performance, dependability, and quality. Built-in features include safety lock-out, freeze protection, and high elevation adjustment.