Sand filtration can be used for salt water

Sand filters work on the natural principle of water filtration. The water permeates the deposited layer of sand which traps small impurities. In this way, the sand naturally becomes clogged and has to be washed, which is what the six-way valve is used for. Turning the valve to the sand washing position reverses the direction of the water flow and thus flushes the settled dirt down the drain. This process can be repeated throughout the lifetime of the sand, which is very high compared to other filtration methods.