Swimming Pool Stores carries a wide array of Sand Filters for your pool or spa. The filters consist of layers of sand arranged with coarseness of texture increasing downward. As a sand filter collects dirt, its efficiency increases, trapping more dirt. When your pressure gauge shows a reading 8 - 10 lbs. over the clean, start-up reading, it is time to backwash the captured dirt out of the filter. Sand Filters are low maintenance.