Sufficient chlorine should be fed to produce the desired residual in the filter effluent. Enough KMnO4 should be fed to produce a “just pink” color in the filter inlet. (Fe) and/or manganese. Step 3: OPEN the out-flowing valve as well as the faucet nearest the system for 5-10 minutes, or until the water runs clear, to flush any fines from the filters.
eBay