Sample of a property tax billWhat to do if No One Knows if a Building is Connected to a Septic Tank or to a Sewer System

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This article explains what to do if you are buying a home or other building and no one seems to know if it is connected to a private septic tank and drainfield (or similar onsite waste disposal system) or connected to a public sewer line. A reader asked, "How do I know if the house I am purchasing has a septic tank?" Often the answer to this question is well known, documented, and everyone is confident of the facts. But in older communities, especially if the age of a building is greater than the age of the community sewer system, even if a sewer is installed right in the street in front of a building, that building may never have been connected to the sewer line.

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What To Do If No One Knows Whether a Building Is Connected to the Public Sewer Line or Not

If an owner or realtor tells you that a sewer system is installed but the house is older than the sewer and no one knows for sure if the house was ever connected to the sewer, some investigation is needed.

Even if we see that there is a sewer line in the street on which the house is located, how do we know if the home is connected to it? 

We can do several things to find out whether a home or other building is connected to a public sewer system or to a private septic tank system:

  1. Find out if a public sewer line is even available for the property or building in which you're interested. there are lots of ways to find out if a sewer main is present. We outline them in the next chapter of this article at Clues Indicating a Sewer System is Present. Obviously if no public sewer is available you'll need to begin a septic tank and drainfield investigation. But it's also worth asking local building authorities if there is a plan to add a public sewer in the neighborhood. Knowing that a public sewer line is coming, and when, can inform your plans for septic system maintenance, repair, and replacement options.

  2. If a local sewer main is right at the property you'll still need to find out if the building is connected to it. See Clues Indicating a Building is Connected to Sewer and don't assume that just because a sewer main is nearby that your building has been connected to it.

  3. Ask local plumbers or septic contractors if they’ve done work on the house or on a septic system there, or if they have worked on sewer main or septic tank connections for other nearby buildings

  4. Ask the town building department if a sewer main is present, and if so, ask if they have records of the property being connected to the sewer;

  5. Look for visual evidence that a septic tank was or remains at the property such as depressions in the ground, stones marking tank or cleanout locations, even wet areas and odors (unfortunately indicating a problem) can indicate that a septic tank or cesspool is present. For older properties you should do this even if the building is presently connected to a public sewer.

  6. Finally, as a last resort you can trace the piping underground to find if it heads to a sewer main passing near the property or conversely, to an onsite septic tank or cesspool. Tracing house waste piping to its destination, whether that destination is a septic tank or a sewer line, is a similar process.

    1. See How to Find the Septic Tank – since these methods can also help you find and follow the course of a buried main drain that connects to a sewer. There are various methods of pipe tracing including simple plumbing snakes and probes and more sophisticated electronic pipe sensing systems


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