Reverse osmosis (RO) is increasingly used to concentrate dairy fluids and generate water that can be used for different purposes in a dairy plant. However, the composition of the dairy fluid used, namely total solids and protein contents, have a direct impact on the performance of RO membrane and on the permeate composition and quality. The objective of the present study was to compare the performance of RO membranes for reclaiming water from skim milk, cheese whey or ultrafiltration (UF) permeate from milk. A 2-step approach using a regular RO thin-film composite polyamide membrane element for the first water extraction, and a high-density RO membrane element for polishing the RO permeate was used. Filtrations were performed in triplicate at pilot scale (60 L batches) using 2.09-m² membrane elements (Parker-Hanifin Corp., CA, USA), at operating pressures between 1.38 and 3.45 MPa and up to maximal water recovery for both membranes. The energy consumption by the filtration system was monitored during experiments. The quality of reclaimed water was also characterized in terms of mineral content (Ca, Mg, Na, K, P and Cl) and conductivity. Process efficiency was assessed by determining the energy requirement to generate water reclaimed from the 3 dairy fluids (kWh/kg of water), and production costs. In the first stage, water recovery was 47, 55, and 60% for whey, skim milk, and UF permeate, respectively. The energy consumption was also lowest for UF-permeate (99 ± 8.0 kWh/kg water reclaimed). In the second stage, the polishing of water reclaimed from the 3 fluids showed similar results with a recovery of 83–86% and an energy consumption of 74 ± 3 kWh/kg water extracted. The conductivity (<25 mS/cm) and mineral content (<1 ppm) of polished water were also low. Overall, reclaiming water from UF-permeate led to a better process efficiency (higher water recovery and lower energy requirement for the first RO step) resulting directly from its low total solids and protein contents. Our results suggest that an appropriate selection of dairy fluid for reclaiming water can improve process efficiency, lead to savings in water reclaiming costs and reduce the dairy plants overall environmental footprint.