Water trap with an emptying device

A breathing gas system and water trap is improved in respect to the reliability of operation and has an emptying device. The water trap has a gas inlet, which meets a first water separating membrane via a connection line. The connection line leads into a water tank located deeper in the incoming flow direction from the first water separating membrane and into a gas measuring device with vacuum on the discharge side from the first water separating membrane from the water trap. The water tank has a rinsing gas flow line, which is arranged above the liquid level, leads upward via a gas-permeable membrane and is likewise connected to the applied vacuum of the gas measuring device. The water tank has a water transport line for emptying the water tank, which water transport line extends into the liquid and is provided with a downstream vacuum via a nonreturn valve and a downstream liquid pump or via a solenoid valve. The water trap is equipped with a filling level detection system, which is connected to a control and analyzing unit. The control and analyzing unit is connected to the liquid pump or to the solenoid valve, so that the water tank can be emptied as a function of the signal of the filling level detection system.