As used in this act, the phrase “township board” means the township trustee, township clerk, and township treasurer, acting as a board. As used in this act, the phrase “sewage system” means the main, lateral, outfall and intercepting sewers which may be constructed by any sewage district within or without the corporate limits of any township as herein provided, including all manholes, pumps, lift stations and other appurtenances to such sewers, including sewage-disposal plants, if any be constructed by such sewage district as herein provided, and their appurtenances. As used in this act, the phrase “public water supply” means a supply of water furnished to residences and other customers in any part of the township through water mains, whether such mains are owned and operated by the township, an adjacent city or township, or by a private utility.