The flexibility and capability of our Rinnai tankless rack system (TRS) allows it to replace just about any existing water heating product, from domestic boilers to traditional tank-style water heaters, as long as the necessary gas, venting and installation requirements are present. In fact, our modular design can handle up to 4.9M BTU. Even in cases where the hot water demands are smaller, Rinnai tankless water heaters can provide significantly more energy efficiency and reliability than tank-style water heaters.