How to find the septic tank or the point at which a building is connected to a public sewer by starting in the building, examining its drain or waste piping.

Whether you're looking for the connection to a public sewer or you're trying to find a septic tank at a property, to start your search it is helpful to first locate point at which the main waste pipe or "sewer line" 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 or public sewer.

But there are exceptions, as we explain here. Septic tank location guide: this document provides suggestions and procedures for finding a septic tank.

Where Does the Main Building Drain Exits the Structure?

In the photo above we could see two interesting facts: first a main drain and cleanout were located in the house rear foundation wall, and second, the toilet drain passed separately through the same rear foundation wall just a few feet away.

But the clothes washing machine was connected to a separate drain that exited behind the washing machine, low in the building wall and nowhere near the main waste line.

While we never bet big on where buried drain lines run, the geometry of the basement of this home made for a small, cramped space.

It seemed likely to us from the angle of the pipes and the ultimate destination of the piping (a septic tank downhill in the rear yard), that the two lines joined outside the home, near the house rear wall, using a wye connector. (That later proved to be the case.)

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.

When a 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.

Videos showing how to find the septic system, septic tank, & septic drainfield are

at SEPTIC VIDEOS.

Also see SEPTIC DRAINFIELD LOCATION - how to find the leach fields. 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.

More tips on finding where a building drain line exits the structure are at

FIND the MAIN BUILDING DRAIN - for clearing a blocked sewer connection or repairing a public sewer connection line

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Continue reading  at POSSIBLE SEPTIC TANK LOCATIONS or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.

Or see these

Recommended Articles

• SEPTIC CLEARANCE DISTANCES
• SEPTIC DRAINFIELD LOCATION
• SEPTIC TANK, HOW TO FIND - home
  • DISTANCE TO SEPTIC TANK
  • FIND MAIN WASTE LINE EXIT
  • POSSIBLE SEPTIC TANK LOCATIONS
  • SEPTIC TANK COVERS
  • SEPTIC TANK DEPTH
  • SEPTIC TANK DESIGN DEPTH
  • SEPTIC TANK LOCATING EQUIPMENT
  • SEPTIC TANK LOCATION SKETCH
  • SEPTIC TANK RISERS
  • SEPTIC TANK GRASS or SNOWMELT
  • SEPTIC TROUBLE SIGNS, OTHER
  • SOAKBED SOIL CONDITIONS
  • SEPTIC LOCATION VIDEO
  • VISUAL CLUES LOCATE the SEPTIC TANK
  • WHO KNOWS SEPTIC LOCATION?
• SEPTIC TANK PUMPING MISTAKES
• SEPTIC TANK RISERS
• SEWER LINE REPLACEMENT - home

Suggested citation for this web page

FIND MAIN WASTE LINE EXIT at InspectApedia.com - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.

Or see this

INDEX to RELATED ARTICLES: ARTICLE INDEX to SEPTIC SYSTEMS

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