Abstract:
A tankless water heater (TWH) isolation valve includes a valve body having a plug valve port, a TWH port, a water distribution system port and a drain port. A plug valve includes at least one plug seal. The plug valve is controlled by a rotatable plug valve handle. The plug valve is disposed through the plug valve port and within the valve body. The rotatable plug valve handle includes a first plug valve handle position and a different rotated second plug valve handle position. In a normal operating mode in the first plug valve handle position, the TWH port is fluidly coupled to both of the drain port and the water system distribution port. In a drain mode, the TWH port is fluidly coupled to the drain port, and the water system distribution port is closed to the TWH port as blocked by the plug seal.