The WXI Hi-Flo unvented water heater is part of Fabdec’s Excelsior range of water heaters, developed at Fabdec’s UK headquarters in Ellesmere, Shropshire, to cater for higher throughput water volumes, using Fabdec’s unique and patented 3S Technology. Described by the company as “the world’s first true selfsustaining system”, it is based on an internal expansion system and offers major advantages. This 3S Technology was pioneered by Fabdec and is a self-sustaining internal expansion system, adopting the Venturi principle in which atmospheric air is drawn into the system as water is demanded upstream.Because this occurs in accordance with hot water demand, it does not cause any deterioration in performance. This process means the internal air gap is permanently replenished, eradicating the need for recharging or regular servicing. There are no internal, moving parts in the cylinder and, once in place, there are no additional parts required. The absence of an external expansion vessel means the tank can fit into more compact installation spaces. This specific product has been modified to meet the demand for higher flows rates within high-end or multiple occupancy domestic residences. It is also suitable for light commercial applications, for example catering or guest houses. To achieve this, the WXI has a new 28mm Venturi valve on the inlet and 28mm outlet fitting. The absence of an external expansion vessel means the tank can fit into compact installation spaces, and Fabdec also offers a pre-plumb version.