Fluid is filtered across slotted filter elements from inside to outside. When pressure drop reaches the set point, detected by a differential pressure switch or transmitter, the back washing is automatically initiated starting the geared motor and opening the actuated discharge valve for two minutes approximately. During back-wash, only one, two or three (depending on the filter model) filter elements at time, through the cleaning arm, are in communication with the drain at atmospheric pressure. Due to the differential pressure between the filter and atmosphere, part of the already filtered water flushes these elements in the reverse way (outside to inside). This action provide to remove the dirty particles from the elements and discharge them through the drain connection. Internal cleaning arms provide to back-wash only a small portion of the total filtering area at time. This design minimize the water discharge and maintain the filter in operation when the back-wash is in progress.

SFH and SPT filtration systems, are designed for industrial water, well water or surface water filtration. Designed for continuous operation, these equipments can be cleaned without any additional external water supply. According to the flow-rate, the inlet water should be handled by one or more filters installed in parallel, connected with common headers.