A pool sand filter is a type of filter that is commonly used in swimming pools. It is made up of a tank that is filled with sand, and a pipe that leads to the swimming pool. The pipe has a valve that is used to control the flow of water into the filter. The sand in the filter traps impurities and debris that are in the water. The water then flows through the pipe and into the swimming pool. The sand in the filter needs to be replaced periodically. Pool sand filters are a very effective way to keep swimming pools clean. They are easy to maintain and can be used with saltwater or chlorine.