The type of water used in brewing is of some importance. Rain water is ideal for use except when gathered in smoggy areas. Tap water can be used as a last resort, but consider purchasing the bottled variety in the future.
Distilled water is definitely better than chlorinated, fluoridated, bacteria-filled tap water.
If it's all you have - use it. If old-fashioned, try making the brew in a fireplace or outdoors over a blaze. They're few exceptions in Herbalism. One is Cauldron brewing. Herbal products prepared with double broilers may also require metal pots.