The owners of all houses, buildings or properties used for human occupancy, employment, recreation or other purposes, situated within the County and abutting on any street, alley or right of way in which there is now located or may in the future be located a public sanitary sewer of the County, is hereby required at his expense to install suitable toilet facilities therein and to connect such facilities directly with the proper public sewer in accordance with the provisions of this chapter within ninety days after the date of official notice to do so, and thereafter to cease using any other method for the disposal of sanitary sewage, industrial wastes or other polluting waters, provided that such public sewer is within 100 feet of the property line and not more than 300 feet from the nearest of such houses, buildings or properties to be served. However, the owner of any such house, building or property that is now served by, or which at the time a public sewer may be made available thereto is served by, a septic tank system or privately owned sewage treatment plant, approved by the County Health Department, as provided in Chapter 1066, and, where required by statute, approved by the State Department of Health and the State Water Control Board, shall not be required to make such connection to the public sewer, provided that such sewage works are operated and maintained at all times in strict accordance with the requirements of such governmental agencies having jurisdiction and are not altered, enlarged or replaced.