Start with the free county records. Hamilton and Clermont counties post septic inspection results online, while Warren, Butler, and the Northern Kentucky Health Department release files on request. When no record exists, the tank is traced from the sewer line, probed, or located electronically, then fitted with risers.
More detail
Where the records live depends on the health district, and all of them are free or nearly free to search. In Hamilton County outside the cities of Cincinnati, Norwood, and Springdale, Hamilton County Public Health publishes an online map of septic inspection results that you can search by address; it is updated weekly and shows each system's inspection history, and older permit files come through the county's public records request form. Inside Cincinnati city limits, the Cincinnati Health Department licenses and inspects the city's roughly 500 unsewered homes each year, so its Technical Environmental Services office holds those files; Norwood and Springdale have their own health departments. Clermont County Public Health has an online septic search in two parts, a database for inspections through December 31, 2018 and its customer self-service portal for 2019 onward. Warren County Health District handles requests by phone at (513) 695-1220 and cautions that some older systems have no record at all. Butler County General Health makes inspections completed before March 2020, septic included, available on request through its Environmental Health division. In Boone, Kenton, and Campbell counties, the Northern Kentucky Health Department has no online search: you file its Open Records Request Form along with its Onsite Sewage Request for Public Records attachment. A county file rarely includes a surveyed drawing for an older system, but inspection reports usually describe where the inspector found the tank, and that is often enough. When the file is empty, check the seller's disclosure (Ohio's form asks who last inspected the system and when; Kentucky's asks for the servicer's name and the date the tank was last cleaned), call the last company that pumped it, then follow the main drain where it leaves the foundation and probe outward along that line. An electronic transmitter pushed through the cleanout or a sewer camera finishes the job when probing fails. Once the lids are found, add risers to grade so no one has to search again; Ohio now requires them on new tanks with at least a 12-inch opening and a secured or 50-pound lid. Our permits by county guide lists each district's contact, and Clermont owners can start with the Clermont County septic guide. Locating is part of a standard septic pumping visit when the lids are buried.