Trionic RV Tanks SelectionTRIONIC offers an extensive line of rv water and holding tanks to meet most size and durability requirements. All tanks are rotationally molded of a seamless one piece, non-corrosive linear polyethylene that meets FDA acceptance. Each water tank has one 1/2" supply opening, one 1-1/2" fill opening and one 1/2" vent. Each holding tank has one 1/2" vent and has two 1-1/2" openings. Openings on all tanks are female National Pipe Threads (NPT) and are located on one end of the tank. We offer custom fitting locations and an optional 3" cleanout or inspection port. All of our tanks are guaranteed to be extremely durable and will not collapse when emptied with high capacity pumps. All tanks can be special ordered with 3/8" wall thickness.