The open filters are Disk Stacks with attachable tube at its downstream side. This simple and inexpensive product can be used for river and reservoir pumping by dipping it below the water level and pumping by suction from the inner chamber.
For agricultural applications such as for low pressure Micro-Drip irrigation, or in the absence of pumps, the SDF™ Open Filters are used as "Open Gravity Filters". In this mode the water is not forced through the filter. It infiltrates through the passageways. The head-loss is minimal and cleaning is easier since dirt particles are not stuck in the passageways