Rinnai Corp. has added the Demand Duo 2 to its commercial water heating lineup. The Demand Duo 2 combines the hybrid technology of the Demand Duo product family with the redundancy and performance of its commercial rack systems. The system features a 119-gallon storage tank along with two CU199 Rinnai Tankless Water Heaters that work together to offer the best benefits of both tank and tankless technology. The Demand Duo 2 offers longer life, lower operating costs, easier serviceability and maintenance, a longer warranty and better technology. The system is also lighter and takes up less space than competitive products, requires no ASME certification or inspections and has the most venting options in the industry.