No. Strictly forbidden by Ohio code and disastrous for the system. Stormwater and groundwater overwhelm the drain field. Route sump and downspouts to dry wells or daylight, never the septic.
More detail
Ohio HSTS rules explicitly prohibit clear-water connection (sump pumps, downspouts, foundation drains, AC condensate) to septic systems. The reason is engineering: a septic drain field is sized for typical residential wastewater volume (200-400 gallons per day for a household of 4). A typical sump pump can discharge 1,500-3,000 gallons per hour during heavy rain, instantly overwhelming the drain field and surfacing effluent across the yard. Downspouts add roof runoff at similar rates. The typical violation pattern in older Cincinnati homes: a sump pump discharge line was tied into the septic line during a basement-finishing remodel decades ago. Inspecting the basement plumbing for unauthorized connections is part of a real-estate septic inspection. Correction: redirect the discharge line to a dry well (gravel-filled excavation in the yard), to daylight (visible discharge to grade away from the foundation), or to a storm sewer if available. Cincinnati basement-finish project watch: many pre-2000 basement-finish projects tied sump pumps into the septic line during installation, before code enforcement caught up. When buying a Cincinnati home with a finished basement and a septic system, walk the basement plumbing to confirm the sump discharge runs separately. Inspectors should catch these but sometimes miss them. If the basement also has rim-joist closed-cell foam or full encapsulation already in place, photograph the area before any new septic work so the foam can be patched cleanly if a plumbing trench has to cross it. Correction is straightforward: redirect the discharge line to a dry well or daylight, $300-$700 typical.