A physically compact (saline) solution preparation apparatus includes a solution mixing tank (10) coupled to sources of concentrate and diluent. A concentrate transport path (16) is configured to both homogenize and deliver concentrate to the mixing tank, while the diluent transport path (12) is controllably purged of potential contaminates prior to supplying the diluent to the mixing tank. A mixed solution transport path (16) recirculates and thereby homogenizes the contents of the mixing container, and actively pumps out solution that has been mixed to a prescribed conductivity-based concentration, to one or more solution on demand storage reservoirs (24) for respective instruments. The operation of the apparatus is based upon measured conductivity of the contents of the solution mixing tank, so that there is no need to conduct precursor volumetric measurements of either diluent or concentrate.