Raw water from the water inlet into the filter and filter from the filter, in the clear water from the connecting pipe into the water storage tank filled, water through the outlet pipe into the clear water tank. Filter layer constantly interception suspended real, caused filter layer resistance of gradually increased, thus prompted siphon within of level constantly increased, dang vacuum degrees reached must value Shi, will occurred siphon role, then pipes in the of water bottom to through filter layer, on filter material for anti-flush, dang flush tank water declined to siphon damage tube Shi, air into siphon, damage siphon role, filter pool anti-flush end, into Xia a cycle work, thus without to other filter device as, not needed equipped with anti-flush pump and anti-flush towers.