I use tap water, but I let it sit out overnight in the watering can to let some of the dissolved gases (like CO2) evaporate. I don't think it's really necessary, but I got into the habit when I kept fish. I also like it to be room temp when adding it to his enclosure.
I give my adults tap water , but baby's get bottle water . Because we as adults can handle arsnic poison and small amounts are in tap water but I don't know about baby torts .