Automatic toilet flush valves are sized to fit tankless toilets. These sensor-operated valves have a spud coupling for attaching to a toilet spud. They typically require a high-pressure water supply to operate.,Automatic flush valves are sensor-operated valves for flushing tankless toilets and urinals. Also known as automatic flushometers, these flow-control devices don't require user contact to activate, so they help decrease the spread of germs. Their sensor automatically triggers flushing after a set time period or once a user has moved out of sensing range. They're ideal for ensuring flushing in public restrooms and high-use areas.