How to Find Your Septic Tank (and the Lid)
Updated · By the Roof to Footing editors
The fastest way to find a septic tank is to check your county or local health department's records for a site plan, then confirm it in the yard by following the sewer line out from the house and probing the soil. Most tanks sit 10 to 25 feet from the foundation, in line with where the main drain leaves the house, with lids buried anywhere from a few inches to a few feet deep.
1. Check the records first
Septic systems need permits, and many health departments keep the permit file, often with an "as-built" drawing showing the tank's location and distances from the house. Try:
- Your county or city environmental health department
- The home inspection report and seller disclosures from when you bought the house
- Past pumping receipts; septic companies often note where the lid is
- Neighbors with similar houses from the same builder
2. Find where the sewer line leaves the house
In the basement or crawlspace, find the main drain pipe (usually 3 or 4 inches) that all the plumbing feeds into, and note where it goes through the wall. On a slab house, look for a cleanout pipe outside near the foundation. The tank is usually straight out from that point, though the line can turn.
3. Look for clues in the yard
- A rectangular patch where grass grows greener, or browns first in dry weather
- A low spot or a slight mound
- Risers or round plastic lids at ground level (newer systems)
- An area kept clear of trees and paths for no obvious reason
- Snow that melts first over the tank in winter
4. Probe the soil
With a thin steel soil probe (or a long piece of rebar), start about 10 feet out from where the sewer line leaves the house, in line with it. Push the probe straight down every 2 feet or so, working outward and side to side. A tank feels like a large, flat, solid surface at a consistent depth; a rock feels small and irregular. Once you find it, probe around to outline the edges.
Before you push anything into the ground, call 811 to have utilities marked. Gas, electric and water lines can be shallow.
5. Dig to the lid
Most residential tanks are rectangular, roughly 5 by 8 feet or so for a 1,000-gallon tank, with one or two lids (inlet and outlet) along the centerline. Older tanks may have a single lid in the middle. Dig carefully with a shovel at the ends of the outline you found.
Never go into a septic tank or lean in over an open one. The gases inside can kill quickly. Keep kids and pets away from open lids, and replace lids securely.
6. Hire a locator if needed
A septic company can run a small transmitter through the line from a cleanout and track it with a receiver, or use a camera. The fee is often credited if they pump the tank on the same visit.
Make it easier next time
Once you've found it, measure the distance to two fixed points (like house corners) and keep the sketch. Consider installing risers that bring the lids to ground level. The EPA recommends having a septic system inspected at least every three years and pumped every three to five years for a typical household, so you'll be back.
If the yard is soggy over the drain field or drains back up after pumping, the problem may be in the field rather than the tank; see drain field replacement cost.