Jobe Topaz Valve 3/4" w/DLT. Topaz trough valves are float operated valves for use in automatic filling of water troughs, tanks, cisterns etc. The valve is configured for above or below water mounting. The float operates a small pilot valve which in turn operates the main diaphragm valve. Topaz trough valves are a good choice where their high flow, compact,robust, non corrosive construction and high level of adaptability are needed.