Hard water and homemade foaming hand soap?

I recently switched to making my own foaming handsoap using Dr. Bronner's unscented soap and water.  I basically fill up the majority of an old foaming handsoap dispenser with water and then top it off with the Dr. Bronner's.  I've noticed two extremes and I'm wondering if it has to do with having hard water at my place.  At first, my hands felt very greasy after washing, so I diluted the dispenser with even more water.  I cannot seem to find a good balance!  When I add more water, I'm left with no foam and it's very hard to dispense the soap.  Is there anything I can add to the dispenser to keep the soap foamy but not greasy?