Drain valve

Abstract

A drain valve is provided for connection to a water supply line for draining water in a vacuum flush aircraft sanitation system. The valve comprises a housing having a fluid inlet and a fluid outlet. The housing also includes a pressure chamber with a diaphragm that is normally biased to a first position by a spring when the chamber is depressurized. This allows water to flow from the fluid inlet to the drain outlet and ultimately to a drain mast of the aircraft. When the chamber is pressurized, however, the diaphragm moves to a second position which operates a linkage mechanism that moves a plug against a seat in the drain outlet to close the drain outlet so that rinse water does not drain from the valve's fluid inlet. A sanitation system also is disclosed, in which grey water from the aircraft lavatory sink is collected and transferred under pressure through a rinse line to flush a toilet bowl when the drain valve is closed. The pressurized lines of the aircraft's potable water supply are used to actuate the diaphragm in the drain valve. Importantly, the drain valve always keeps the pressurized potable water separate from the grey water to prevent unwanted contamination of the aircraft's potable water supply. Moreover, draining of the grey water is automatic upon depressurization of the potable water supply lines.