Treating surface waters from reservoirs usually means the removal of manganese and particles as well as the adjustment of pH to reach calcium carbonate equilibrium. A new combination of limestone filtration and ultrafiltration (UF) was investigated in pilot experiments. Results on particle and manganese removal efficiency and specific permeate flux dependence on backwash procedure are discussed and aspects for further research are shown. The full-scale concept of a new water work based on the pilot experiments is presented. Costs are discussed for the comparison of membrane technology to conventional direct filtration.