Automatic drain valve

A toilet system comprising:

• a toilet;
• and
• a drain valve assembly for draining waste water from a toilet bowl,
• the drain valve assembly comprising:
• a valve housing having an upper section and a lower section,
• the lower section comprising an inlet port, an outlet port and a water collection chamber between the inlet port and the outlet port,
• the upper section including a pressure diaphragm across the upper section;
• a poppet valve positioned in the housing and extending between the lower section and the upper section,
• the poppet valve arranged to fluidly seal the lower section from the upper section, the poppet valve in the water collection chamber being arranged to be normally sealingly positioned across the outlet port to prevent water exiting the water collection chamber to the outlet port,
• the poppet valve attached to the pressure diaphragm in the upper section, the drain valve assembly further comprising a pressure line for providing a pressure signal to the upper section such that when the pressure from the pressure line in the upper section exceeds a predetermined opening pressure it causes the pressure diaphragm to lift and to thus lift the poppet out of sealing engagement across the outlet port such that water can drain to the outlet port from the water collection chamber;
• wherein the poppet valve has a hollow body defining a channel from a first end of the poppet valve, adjacent the outlet, and a second end of the poppet valve adjacent the pressure diaphragm, and
• wherein the housing defines a vacuum cavity across the second end of the channel, such that a negative pressure acting on one end of the poppet valve is balanced by a negative pressure acting in the opposite direction at the other end;
• wherein the pressure line is an air-filled fluid conduit fluidly connected between a bottom of the toilet bowl and the upper section of the valve housing such that water flows from the toilet bowl into the conduit such that when the level of water in the toilet bowl is at a predetermined flood plane level, the level of water in the conduit is such as to compress the air in the conduit to a pressure sufficient to open the poppet valve.