The nozzles must be positioned in the upper part of the tank where possible. The following recommendation applies:
You will also need to make sure enough cleaning fluid strikes the tank top. Nozzles are generally placed at the center of the tank if there are no baffles or agitators located inside. Tanks with baffles and agitators may require more than one nozzle because nozzles work under a "line of sight" principle and spray shadowing can occur.
There are several factors to consider when selecting and positioning a tank cleaning nozzle for your application, however, Lechler's Tank Clean Simulation Software can make your job easier.