How do sand filters work?
Water is pushed into sand as it passes through the sand dirt is trapped between the granuals of sand at the top of the filter. at the bottom of the filter in the sand there are spokes with holes in them big enough to let water through but not big enough to let sand through (unless they are worn) known as laterals. these allow the water to return to the pool. As the dirt at the top of the sand builds up the the pressure of the water being pumped to the filter builds up slowing down the turnover of water being filtered. When the pressure becomes too high the laterals at the bottom of the filter are shut of and the water at the top of the filter is allowed to run directly to waste as it does this it takes along dirt that has accumulated. when the water runs clear again( there is usually a little indicator that sows the water running through it at the top of the sand filter while it is backwashing)You set the filter back to rinse for about 30 seconds then back to filter filter from back wa
