Does tap water rinse as well as purified water?
As far as detergency is concerned, tap water will rinse just as well as any purified water. Rinsing is a mass displacement mechanism and in itself does not depend on the purity of the rinse water. The reason to be concerned with the purity of the rinse water is that whatever is in the rinse water can deposit on your instrument when the water evaporates away during drying. In the case of medical instrument cleaning, the primary concern would be anything that would interfere with the following sterilization step. Any reasonably clean tap water will rinse away the detergent/residue mixture left on the instrument from the cleaning process and would be clean enough that it would not leave a pathogen shielding film or residue that would inhibit the sterilization process. In instances where chemical disinfection is being used without a further sterilization step, then it can be critical to use high purity water to rinse with, however when rinsing is intermediate to a final sterilization step, there is greatly reduced risk of cleaning and sterilization failure due to the rinse water. You do run the risk of water spots from calcium and magnesium deposits in the event that the tap water has a high mineral content. This can be minimized by wiping instruments dry or shaking them off to remove water droplets. In either case, even if incidental water spots are formed, water spots would not cause sterilization failure.