A pressure tank in a constant pressure system is typically much smaller than in a conventional system. In a constant pressure system, the tank stores very little water acting primarily as a buffer to prevent pressure fluctuations.
Pumps used in a constant pressure system are basically the same as those used in a conventional submersible system. The difference is the motor attached to the pump runs at variable speeds depending on water demand. The motor speed is controlled by a variable frequency drive controller. Depending on the specific system, the motor could be a single or three phase unit.