A process for a therapeutic bladder pressure estimator is operative with a pump connected, in sequence, to a first hose, a supply pressure sensor, a second hose, a bladder having an inlet coupled to the second hose, a bladder outlet coupled to a third hose of substantially equal length to the second hose, a return pressure sensor, and a fourth hose coupled to the return pressure sensor and returning fluid from the pump to the reservoir. The process forms an error signal from the difference between a setpoint and the average of the supply and return pressures. A head pressure measurement may be done by turning the pump off after a steady state reading is made.