They work by centrifuging the water so that the heavier particles descend, separating, normally used to remove the sand that comes along with the water coming from holes. They can be automated through a solenoid valve mounted on the bottom of the filter connected to a programmer by time. Most used filter in groundwaters.
They work with the water passing slowly by a determined volume of sand, being itself the filtering element retaining the particles mainly the clays and algae. For washing, simply reverse the direction of the water and at the same time open an escape. It can be automated with solenoid valves and with a programmer that can operate by time and/or by pressure difference between the inlet and outlet of the filter. This system is usually used as a prefilter in surface waters (dams, rivers or canals).
They work with the water passing through a network cartridge / stainless steel mesh where particles larger than mesh size are retained. To wash when they are manual they have to be disassembled and the accumulated particles removed, when they are automatic they have a scanner that sucks the mesh. When they are automatic they can be hydraulic, needing two and a half pounds of minimal pressure to clean, or electrics that work without great requirement of minimum pressure. This type of filters is used for water with less dirt, or often used as fuse of the installation getting assembled following the sand filters.
They work with the water passing through a set of rings tightened between them so that the larger particles cannot pass between the grooves of the ring. For washing when they are manual, they must be loosened so that the rings are loosely engaged with each other in order to remove the particles which are retained in the groove and in the part outside the cylinder which comprises a group of rings; when automatically connected to a programmer the system reverses the direction of the water and at the same time creates space of gap between rings. This system is usually used for water with less dirt or often used as fuses of the installation getting fitted following the sand filters.
Depending on the water flow you need to filter, one or more filters (sand, rings or mesh) can be associated. Filter batteries can be manual or automatic.