Nope. I have never done this.
Yes. Ordinary tap water can be harmful, as Tap water has contaminants which build up in the battery like minerals, which will build up over the battery plates clogging the pores. If tap water is used in the battery, it will cause it to work even harder and become hotter, causing it to wear out faster.
The best way to fill a battery is with de-ionized, de-mineralized or distilled water. Use only distilled water to fill the cells. If the electrolyte levels in the cells are low (plates are exposed), fill each cell to cover the plates. Then use a battery charger to recharge the battery, or just drive the car for a few days in normal service.
(Content taken from different sources on the internet)