GB576305A - A new or improved back-flow prevention device for plumbing systems - Google Patents

Abstract

576,305. Water-waste-preventing cisterns. LANGDON, J. D. April 6, 1943, No. 5486. [Class 26] [Also in Group XXIX] A flushing or other device for connection to a plumbing system comprises a pressureoperated valve 8 supported in a casing 1 open to the atmosphere at 21, 21a and having a bottom outlet 3 for connection to a plumbing fixture. At the discharge end of the valve is a nozzle 7 having an area substantially less than that of the outlet 3, its discharge capacity under pressure of the supply to the inlet 9 being so proportioned to the flow capacity of the outlet 3 under gravity flow as to permit water to back up into the casing 1 to a level above the lower end of the nozzle. The openings in a supporting bridge 4a should have an area preferably more than eight times that of the nozzle 7, and the area of each opening 21, 21a should be four times that of the outlet 3. When a handle 19 is tilted, thus lifting a relief valve 16 into the dotted line position, the inlet pressure raises a valve piston 14 from its seat and flow commences. Flow ceases subsequent to the release of the handle, when the piston reseats due to the entry of water into the chamber 12a through a passage 15. A packing member 13 forms a guide for the stem of valve 16 whilst allowing some lateral displacement of the latter.