With ultra-high performance and unprecedented space-saving installation flexibility, the S20W offers heating contractors multiple benefits for a variety of new installations as well as for retrofit projects, NTI Boilers states. Featuring an industrial size stainless-steel coil, and with its capability of 445 GPH first-hour recovery rate, the 20-gal. S20W exceeds most industry standard 50- and 65-gal. indirect tanks, the company notes.