ZPG-type filter backwash principles: 
 1, backwash filters - filters work 
 Normal working hours, turning the water valve is turned on. Filter the water to be disposed of after use by the principle of inertia and the water impurities and small particles suspended solids deposition due to inertia in the vicinity of the sewage outfall. 
 2, filter backwash - rinse sewage 
 Normal washing, the water turned the valve to open. When the filter small particles retain water impurities and suspended solids particles reach a certain number, it will open the valve on the outfall, which will stick out of the role of water in the filter section of the part of the impurities collected until discharge wash water is clear so far. Then turn off the filter on the outfall into the normal working condition. 
 3, filter backwash - backwash discharge 
 Backwash, the water valve is turned off, the drain valve open, then the water was forced through the filter of the inlet tube into mesh with the outer shell laminated filter cartridge, reverse flush from the network adhere to the outer tube impurities on the mesh, to achieve the purpose of cleaning the filters. As the steering valve closed, water flow rate through the recoil valve increases, backwash effect.