The data and observations presented in this paper open up some interesting thoughts and ideas for the management of finished water aluminum residuals. Certainly the precise mechanisms are beyond the scope of this study and bear careful investigation by interested researchers. Some summary statements can be made that reflect on possibilities rather than proclaim therorems. 1) In nearly all water treatment plants surveyed the implementation of polyaluminum hydroxychloride coagulants produced operational benefits and overall economies in treatment. 2) In comparison to previous alum treatment and neighboring plants on the same watersheds, finished water aluminum residuals were lower in every case using polyaluminum hydroxychlorides (PAC1). 3) The implementation of polyaluminum chlorosulfate (PACs) treatment reduced finished water residuals in many of the waters surveyed versus alum, but averaged higher effluent levels versus PAC1. 4) The precise mechanisms of reduction are not clearly understood but may include increased operator attention, lower applied aluminum levels, improved performance of the coagulant itself, and the nature of the aluminum species or aggregates in PAC1 products which only slowly release hydrolyzable and/or complexable soluble aluminum species.