Cationic polymer doses were reduced at two East Bay Municipal Utility District (EBMUD) treatment plants based on prior work conducted at the District indicating that the diallyldimethylammonium chloride (DADMAC) cationic polymer was a significant source of N-nitrosodimethylamine (NDMA) precursors. Recycled filter backwash supernatant was a significant source of NDMA precursors, possibly due to residual cationic polymer. When filtered water was chloraminated with chlorine and ammonia added simultaneously (in batch samples), elevated NDMA concentrations were formed during recycle. When filtered water was free chlorinated first (in batch samples) this recycle stream did not form increased NDMA concentrations. Distribution system monitoring trends were consistent with expectations based on prior experimental results. NDMA concentrations in the chloraminated distribution system decreased when the cationic polymer doses at two treatment plants were decreased. Out of five distinct treatment and distribution service areas operated by the District, the lowest concentrations of NDMA were observed in the service areas that receive water coagulated at low polymer doses, without the input of filter backwash recycle. Ammonia, nitrite and nitrate did not form NDMA with DADMAC; a chloramine residual was necessary for significant levels of NDMA to be formed. This would indicate that nitrification in the distribution system is not likely to contribute to NDMA formation for the current precursor material. Includes 6 references, tables, figures.