How to find the septic tank: to start your outside search, locate point at which the main sewer line leaves the building. The main waste line exit point at a building often points to the direction and sometimes right to the septic tank. But there are exceptions, as we explain here. Septic tank location guide: this document provides suggestions and procedures for finding a septic tank.
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When the septic tank needs to be pumped, a regular maintenance task, the cost of that service will be less if the property owner found the septic tank location and perhaps even uncovered the septic tank pumping access cover.
Other reasons to find the septic tank include inspecting and testing septic systems when buying a home or for safety, to assure that the septic tank cover is in good condition.
This article tells us how to locate a septic tank when it's placement is not already known or when the location of the septic tank is not visually obvious.
If there are no obvious clues outside that clearly mark the location of a septic tank, we can find some critical clues about septic tank location by looking inside the building. Here they are:
Find the main waste line exit point
Look in the lowest level of the building such as basement or crawl space to see where the Main waste line exits the building. The line from house to tank begins outside the house wall at this same point.
Main Drain Single Exit Point
Usually, inside the building the waste drain lines run to a single exit point at the building wall or in the building lowest level floor or crawl space. In the photo above you can see the main sewer line leaving the building low on the wall near the basement corner.
In the photo at the top of this page we have located a sewer line where it leaves the basement wall. Just outside we would expect to find this same sewer pipe. From that point the buried main drain line connects the building to its septic tank.
Particularly for sites where there are not obvious outside clues, this is where to begin your search for the septic tank - inside the building, following its drain lines.
Outside Septic Waste Line Vents Can Point to the Septic Tank Location
At some buildings you may see a 4" to 6" diameter vertical pipe rising from the soil near the house wall, often with a mushroom-shaped cap on top, or you may see such a pipe protruding horizontally through the building foundation wall and extending for a few inches, covered by a cap or by a perforated cover. Sewer line vents are often vents installed on the main waste line.
Finding one of these sewer line vents in a building wall or protruding from the soil outside is another way to spot where the main waste line is exiting the building.
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