All such grants shall reserve to the City the right to purchase or lease all the property of the utility used or useful for the operation of the utility at specified intervals of not more than five years to be stated in the ordinance, at a price fixed, either in the ordinance making the grant, or to be fixed in the manner provided by such ordinance, which price shall in no event include any value for the grant. Nothing in said ordinance shall prevent the City from acquiring such property by condemnation proceedings or in any other lawful manner, which right shall be in addition to those reserved in such ordinance. Upon acquisition of such property by purchase, condemnation or otherwise, all grants shall be at once terminate.