This poll was done about almost 2 yrs ago on here and most said they just use good ole tap water.
I use reptisafe just because i always have from day one. It isn't just for turtles. It is just a water condition that takes out the chemicals in tap water and has some electrolytes in it.
Heck I don't even drink the tap water from Fairfax cty I sure wouldn't want my Ozzy drinking it

Just think of the water sources they drink from in the wild, I am sure tap, well etc won't hurt'em. Long as you keep it fresh it's all good.