Metropolitan Water District of Southern California (MWDSC) provides drinking water to a majority of Southern California residents. MWDSC is currently considering the addition of a reverse osmosis system (RO) to their conventional filtration treatment facilities. Previous research has indicated that residuals from the coagulant they currently use cause degradation in the RO membranes. We have performed work to experimentally determine the optimal conditions to prevent degradation while still properly cleaning the drinking water.