A. O. Smith’s Adapt®+ Premium condensing gas tankless water heaters deliver robust, on-demand performance and the flexibility to install in practically any residential setting. Easily add scale prevention protection by replacing the bypass cartridge with an optional X3 cartridge sold separately — which can make the heat exchanger last up to three times longer than a standard tankless water heater while maintaining like-new performance. The Adapt® line features a built-in Control Display for setting and reviewing up to two recirculating schedules, as well as checking heater status and error codes. Manage temperature settings and activate the heater and recirculation remotely with optional kits (sold separately). All models are ENERGY STAR® certified and extremely efficient with a Uniform Energy Factor of 0.95 and also comply with Ultra-Low NOx regulations. All Adapt® models are field convertible from Natural Gas to Liquid Propane, kit included, and can be installed indoors or outdoors (with an Outdoor Vent Cap Kit sold separately). Cascade up to 12 like heaters together for larger applications requiring multiple water heaters to work in conjunction, cable included.