point of use systems, it is best combined with an educational program about safe storage, filter cleaning, and other recommended practices. The advantages of ceramic filters are their ease of use, long life (if not broken), and fairly low cost. Disadvantages include possible recontamination of stored water since there is no chlorine residual and a relatively low flow rate - typically one to two litres per hour. Sand filtration These filters use sand as the filtering medium. Sand filters look like large balls and they hold hundred of pounds of sterile sand. Water flows into the top of the filter housing and makes its way down through the sand bed where the sharp edges of the sand catch the particulates. On a micron-to-micron comparison, sand filters remove the least amount of dirt – particles as small as 20 to 25 microns. However, sand filters certainly are efficient enough to keep just about any pool clean. To keep a sand filter working, depending on the size of the filter you must clean it as often as once a week. Maintenance means backwashing where the flow of clean water is reversed back into the filter. The problem with this, however, is that backwashed water is simply wasted. A typical backwashing session can waste a few hundred gallons of water – water that must be replaced. Polymer fiber Polymer fiber filters, sometimes arranged into filter balls, are often made of polyethylene terephthalate and are designed to last longer than conventional filters and have a lower environmental impact. See also Hot tub History of water filters References Water filters