Many pressurized sewer systems do not reach their design capacity discharge due to enlarged resistance in the pipe system. An extensive investigation has brought to light that air pockets in pipe systems are an important cause of high resistance in sewer system pipe lines. Air intake by pumps in sumps is one of the main reasons of air pocket formation in sewer systems. But there is still little known about air entrainment due to plunging jets from circular open channels, and air intake by submersible pumps near plunging jets, especially at the scale of real sewer sumps. The research objective is to achieve knowledge and insight into air entrainment from free overfall water jets from horizontal open channels and air bubble intake with submersible sewer pumps. The main questions are: - How does the air entrain into the reservoir? - Where and how many air bubbles can be expected in a certain configuration without any specific measures? - What is the sphere of influence of the submersible sewer pump? - What is a robust measure to prevent air coming into the sewer pump?