What is Pre-filter or Sediment Filter..? A pre-filter or sediment filter in an RO (Reverse Osmosis) water purifier is typically the first stage of filtration in the RO system. Its main function is to remove large particles and sediments from the water before it enters the RO membrane. How Its work in RO Water Purifier..? As the water flows through the sediment filter, larger particles such as dirt, sand, rust, and sediment are trapped by the filter media. These particles are too large to pass through the pores of the filter and become trapped on its surface now filtered water free from larger contaminants, continues to flow through the RO system. By removing these larger particles, the sediment filter helps to protect the delicate RO membrane from damage and clogging. Why Sediment Filters are important..? Sediment filters are essential components of RO water purifiers because they protect the RO membrane, maintain water quality, prevent clogging, and contribute to the efficient and reliable operation of the system.