Cartridge filters are very proficient at polishing water down to 1 micron and less. However, they are a commodity item that must be manually removed, disposed of and replaced when the pressure drop across them becomes unacceptable for the application. Orival filters can often remove more than 90% of the TSS thus allowing the cartridge filters to polish and last many times longer than would otherwise be possible. Orival self-cleaning filters followed by fine cartridge filters are often used for pretreatment before reverse osmosis membranes.