How Automatic Backwash Filters Achieve Backwashing

Automatic backwash filters are intelligent filtration devices capable of self-cleaning without interrupting system operation. Their core innovation lies in using the filtered water itself to flush away accumulated contaminants .

The Filtration Stage

During normal operation, water enters the filter and passes through a stainless steel filter element. Coarse particles are first trapped by a pre-filter screen, while finer impurities accumulate on the inner surface of the fine filter screen . As contaminants build up, a pressure differential develops between the inlet and outlet.

Triggering the Backwash Cycle

The filter continuously monitors this pressure difference through a differential pressure transmitter. When the pressure drop reaches a preset value (typically 0.4-0.5 bar), the control system automatically initiates the cleaning process . Alternatively, cleaning can be triggered by a preset time interval.

The Backwash Process

During backwash, the system opens a drain valve while keeping the main flow operational. Several cleaning mechanisms exist:

Suction Scanner Method: A rotating suction nozzle moves across the filter screen's surface, creating localized negative pressure that draws debris away and flushes it out through the drain port .

Reverse Flow Method: The flow direction is temporarily reversed, causing filtered water to wash back through the screen from the clean side, dislodging trapped particles .

The entire cleaning cycle takes only 10-60 seconds and consumes minimal water (0.08-0.6% of total flow) . After cleaning, the pressure differential returns to normal, and the filter resumes standard operation until the next cycle. This automation makes these filters ideal for unmanned facilities and critical applications requiring continuous water supply.

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