Abstract: A union nut is installed over a valve body between an outwardly flaring flange on a valve port and the valve itself. The union nut is uniquely characterized by installation threads cut into an inwardly flaring shoulder, and installation threads are also provided on the flange of the port. The shoulder can be screwed onto the flange until the union nut freely rotates about the port. A split ring is installed against a neck on the port, the neck being adjacent the flange, such that the union nut cannot threadedly engage the installation threads. The freely rotating union nut can be tightened into a suitable fitting that is part of a fluid system.

Abstract: A service valve assembly for a tankless water heater incorporates one or more features that provide safer operation and easier installation of a valve assembly. Installation of a valve assembly is facilitated by foreshortening all perpendicularly protruding ports, thereby increasing the rotational freedom during installation. A main valve and a drain valve are intentionally distinguished from each other by providing different port sizes, valve handles and valve shapes that change the overall shape and characteristics of the valve assembly in such a way that accidental opening a drain port becomes much less likely. Installation can further be simplified by using a unique union nut that allows a service valve to be easily connected to an existing tankless water heater.