My mom's vet said distilled for crystals.

Dog food is made to provide needed vitamin/minerals. Spring water is not regulated as far as the amount of various minerals, so it would vary by brand/batch. The minerals like calcium are what forms the crystals, so distilled was what her vet wanted her to use.

 

Distilled water has its benefits, as does Spring water. Yes, Spring water does have minerals--that come naturally in nature. They are often more easily absorbed because of being stratified in liquid. Dog food does have vitamins and minerals which are often fortified for specific needs. They don't, however, replace those provided in natural food and water. Stones are difficult, and I feel for your dog. Unfortunately, your dog, just like humans, needs a certain amount of calcium for their bone health. This is one of those, "damned if you damned if you don't" kind of situations. Eliminating a food or supplement essential can be as harmful in some respects--cause another problem--as giving them too much. I think I would err on the side of overall good health in the hopes of the problem not arising again. The other side of this discussion could be a natural predisposition your particular dog has to getting stones. (I hate it when that happens.) Spring versus distilled isn't an issue for me. Good overall health and nutrition is . . . and I'm not inferring you aren't doing a great job. I assume, unless otherwise proven, that we all do--those of us who really care about our animals. Good luck!