A constant pressure system uses a motor controller that runs the well pump at varying speeds, depending on water usage demands. A standard system has a 20 psi window for replenishing water used. As water is used, the tank pressure may have to drop to 40 psi before the pump starts; the pump will continue to run at full speed until it builds to 60 psi. (Note, this 20 psi window can be set to start and stop any 20 psi window – e.g., 45 to 65 psi.) A constant pressure system typically has a 2-5 psi window, allowing for appliances – like point-of-use hot water heaters – to retain a constant flow rate. A constant pressure system is most noticeable when doing the laundry and showering at the same time.