Older homes built prior to the mid fifties may and probably due have ungrounded electrical circuits. The light located in the basement of a 70 year plus home was grounded to the hot water pipe, this method of grounding is incorrect and an electrical safety hazard. All grounds must be to a cold water pipe so the discharge will go to ground. The grounding wire must be copper and the proper gauge. Any electrical switches or outlets that can not be grounded, for example, a non grounded 3 prong outlet located on the main floor can be grounded to a cold water pipe if accessible. All electrical work performed should be inspected by a licensed electrician.