Cal. Water Code § 31103

Upon providing a sewer system in any area of the district the district may declare the further maintenance or use of cesspools or other local means of sewage disposal in such area to be a public nuisance and may require all buildings used by human beings to be connected with the sewer system within such period not less than ninety days from the completion of the sewer system as may be prescribed by the district; provided, that such buildings to be connected are within one hundred feet of the system.