Filter systems for removing fine particles from water comprised of a tank with a filter medium made of sand or cloth and a backwash system for the filter medium comprised of pump operated spray nozzles or air-lift pump with separation chamber; sand filter for commercial pool; sand filters, activated carbon filters for filters with any other granular material for iron, manganese and nitrate biological removal from water, namely, filtering units for domestic, municipal and industrial water purification; solid separator device, namely, a separator body, an impeller and motor used to separate sand, silt and other solid particles from the water; heat exchangers not being parts of machines; fibrous filtering media for general industrial use in the purification of air and industrial fluids; fluid filters, namely, water filters; air filters for air conditioning units