Chlorinated tap water rarely kills an established plant, but freshly cracked indica seeds and their first roots are far more sensitive to it and to very hard water. Letting a bucket stand for a day deals with chlorine, though chloramine needs a filter or a drop of dechlorinator. Water hardness readings that members found workable for seedlings, along with which filters they used, are summarised on https://kushindicaseeds.com in the beginner section. Rainwater has been the simplest fix for me during the first two weeks.
