The commission may increase the capacity of any waterworks, plant or plants owned by it, either by the construction and erection of new and additional buildings or otherwise, and the purchase of other or larger pumps, machinery and apparatus; extend any system of water distribution either within or without any municipality authorized to be supplied by it, by laying additional mains or lateral connections, or by relaying or enlarging existing mains and pipes, as the commission shall deem necessary; and cause to be constructed additional pipe lines or mains to connect any reservoir or water supply in its control, located outside the limits of the municipalities represented by the commission, with any reservoir or supply pipes or mains within such municipalities.