Four things: where the tank and field are, the tank size, when it was last pumped, and what not to put down the drain. Pull the permit record from the county health district, then plan on pumping every three to five years.
More detail
Start with the paperwork, because it answers most of the rest. Septic permits and as-built drawings are held by the county health district, and Septic permits, as-built drawings, and any point-of-sale requirement are held by the county health district covering the property, and they differ between districts across Franklin, Delaware, Licking, and Fairfield counties. A permit record typically gives you the tank size, the system type, the installation date, and a site drawing showing where everything is buried. That single document saves a locating fee later and tells you whether you have a conventional tank and leach field or something that needs more attention. If no record exists, which happens with systems installed before local permitting tightened, the tank can be located by probing or by tracing the main line out of the house. The lid is usually 10 to 25 feet from the foundation on the side the plumbing exits. Pumping cadence for a conventional system in Greater Columbus and Central Ohio runs every three to five years. Household size and habits move that: a family of four in a 1,000-gallon tank sits near the three-year end, a couple in a 1,500-gallon tank stretches toward five, and a garbage disposal adds roughly 50 percent more solids and pulls the interval in to every two to three years. One worthwhile upgrade in the first year is a riser, which brings the access lid to grade so future pumping does not require digging. It runs $200 to $400 once and saves the excavation charge on every visit afterward. The expensive mistake to avoid is treating a septic system like a sewer connection. A drain field replacement runs $8,000 to $15,000 and the pumping that prevents it runs a few hundred.