BRV 18L (4.75USG) Expansion Tank Kit for use in all solar thermal and hydronic heating applications. Convenient automatic dual check valve assembly makes installation and tank maintenance convenient, and virtually leak free. Automatically disconnects and isolates both system and expansion tank during tank removal so that expansion tank can be discharged and replaced without depressurizing system. Also allows pressurized tanks to be drained in a outside location, reducing opportunities for spills and leaks. Flat face gasket type unions connections for simplified installation. Each package contains (1) Zilmet 18L High Temperature Expansion Tank, (1) Mounting bracket, (1) Auto-Disconnect Valve Assembly, (1) EPDM gasket, and (1) Mounting Screw Package.