The valve unit, which works pneumatically, consists of the vacuum valve (diaphragm type) and the associated controller. Vacuum valves are all-purpose, easy to maintain valves with a long design life.

There are two types of units:

- the 50mm dia unit is normally installed, but where flow rates are high, e.g. restaurants, hotels and public buildings,
- the 65mm dia unit is recommended. The pinch valve was developed for special applications in non-European countries. Its robust construction and 75mm dia clear flow path makes it particularly suitable for high flow rates and wastewater with high solids content.

Vacuum valves do not require electrical connections. The valves are activated pneumatically by rising water level in the collection sump.

The function of the controller is to open the vacuum valve when the level of wastewater in the sump of the collection chamber is rising, and to close the valve after the batch volume and a preset amount of air has been evacuated from the sump. Valve opening times and air-liquid flow rates can be adjusted optionally by the controller.