6. A FLOATING DIAPHRAGM FOR A FLUID DISTRIBUTION PRESSURE TANK COMPRISING: A FLAT FLEXIBLE HOLLOW DIAPHRAGM, MEANS DEFINING AN ENDLESS ANNULAR AIR AND FLUID TIGHT CHAMBER WITHIN SAID DIAPHRAGM, A FLOAT RING WITHIN SAID CHAMBER COMPRISING TWO LIKE FLEXIBLE HOLLOW TUBULAR MEMBERS, EACH TUBULAR MEMBER BEING SEMICIRCULAR IN SHAPE AND DISPOSED RELATIVE TO THE OTHER TUBULAR MEMBER SO AS TO BE COMPLEMENTARY IN FORMING A COMPLETE RING, RESPECTIVE ENDS OF ONE TUBULAR MEMBER BEING SPACED IN RELATIVELY CLOSE AXIAL ALIGMENT TO RESPECTIVE ENDS OF OTHER TUBULAR MEMBER, AND RESPECTIVE RESILIENT HINGE MEANS FOLDABLE UP TO ONE HUNDRED AND EIGHTY DEGREES AND CONNECTED DIRECTLY TO RESPECTIVE OPPOSED ENDS OF SAID TUBULAR MEMBERS SO AS TO SERVE AS A CLOSURE FOR SAID ENDS AND ALSO AS MEANS FOR NORMALLY MAINTAINING SAID TUBULAR MEMBERS IN A FLAT PLANAR POSITION.