Crystal Pool (PVT) Ltd. Sangabo Mawatha, Anuradhapura 0716552500 crystalpool.lk Sand filters are cleaned by backwashing, which entails reversing the water flow in the filter, and flushing the dirty water right into a squander line. We design architectural plans for swimming pools, planning of costing Monthly bill of Quantities (B.O.Q.) https://www.google.com/maps?cid=3232803549851328223