A septic as-built is the final drawing filed once a system passed its open inspection: it typically shows the tank's location and capacity, the drainfield's layout and size, the system type, the setbacks to wells and property lines, the approval date, and the design flow (usually tied to bedroom count) the system was permitted for. For a buyer, that last item, design flow versus the house's actual bedroom count, is often the single most useful comparison on the page.
• Tank location, capacity and configuration (single or multi-compartment)
• Drainfield or dispersal area layout, size, and type
• System type (conventional gravity, pressure-dosed, aerobic treatment unit, mound, and so on)
• Setbacks to the well, property lines, foundation, and surface water
• The design flow the system was sized for, generally set from bedroom count under most state codes
• Approval date and the office that issued it
• Often the soil evaluation or percolation test results that drove the drainfield sizing
Design flow, and therefore tank and field size, is set from the number of bedrooms the system was permitted to serve, not the square footage of the house and not how many bedrooms exist today. If a house has been expanded since the system was permitted, or a room has been converted into a bedroom without a corresponding permit update, the as-built is often the only place that discrepancy shows up before you own the property.
An as-built is a record of what was approved and, ideally, built at the time; it isn't a current condition report. A system can be built exactly to a correct, matching as-built and still be failing today from age or neglect. That's what the inspection is for. Use the as-built and the inspection together, not one instead of the other.
We hold recorded septic as-built drawings and parcel-level septic-versus-sewer classification for thousands of US counties, with the specific office that holds each county’s records. Generating a code-referenced septic design for a parcel is free.
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Related but not identical. The permit authorizes the work; the as-built is the final drawing filed once the system passed inspection and shows what was actually built, which sometimes differs slightly from the original design.
No. It tells you what the system was approved and built to do at the time. Current condition is what the inspection is for.
It can mean the system predates recorded as-builts in that county, or the file was never digitized. See our guide on unpermitted systems and how to find records before closing.
Reviewed 2026-08-31 against the official sources linked above (where a source is cited) or, where none is cited, left deliberately general. Laws, lender overlays and local ordinances change; confirm current requirements with the county or state agency, your lender, and a licensed inspector before you rely on this for a closing.