When new developments are opened up, it can be quite expensive to build a sewage network with a suitable downward fall. In such cases, a vacuum sewer network offers an interesting alternative to traditional sewer systems. The wastewater is transported to the pumping station under vacuum, which allows significantly smaller pipes to be used and stretches of upward slope spanned. A central vacuum pumping unit conveys the wastewater from households via a central sewage discharge into the public sewer system. An ultrasonic sensor cannot function in a vacuum.