I'm not sure if this has been mentioned just yet, but if you're having problems with hard water you can always use heated up distilled water for your wash or rinses... Like mixing baking soda and distilled water, rinsing with distilled water, and following up with your normal tap water to get the rest of the residues out, maybe even doing one more rinse of distilled water at the end.
Distilled water is technically the softest water out there, so I figure it would be a good idea to try it out and see if it helps rinse out your shampoos/oils.
updated by @calipark: 01/13/15 08:55:58PM