Septic Systems: Buying Land by Soil Type

     If you're dreaming of building a new home on your own land and haven't bought land yet, one of the things to think about is a septic system. There are different types of systems, and the type you choose will largely depend on soil type. Come to think of it, "choose" is probably the wrong word—the soil type, along with the government entity that regulates on-site sewage disposal systems will "dictate" the type of septic system.


    What system is best for your home

    If you have a strong preference, definitely do your research on what type of system a particular piece of land will require. If you don't have a strong preference, it might be a good idea to do some research on the various systems and their pros and cons before you commit.

    There is some really good information on septic systems, maintenance, service contracts, and soil analysis available from the National Environmental Services Center.

    The Standard System

    The percolation test, or perc test, is the biggest factor in determining which type of system is best. This test involves digging three holes of a certain depth, pre-soaking them with water, then refilling the water to a certain level and timing the water level drop to determine the soil's ability to allow water to percolate through it. If the water percs fast enough, you can use the standard tank and drain-field type system. This is the system most people think of when they use the term septic system. It has no mechanical parts, so it's simple and the most reliable, assuming it is installed and maintained properly. However, it requires a soil type that drains well.

    Aerobic System

    On the other hand, if the water doesn't perc fast enough, you'll need a different type of system—most likely what's known as an aerobic septic system. The aerobic system relies on a different type of bacteria to dispose of the waste, which requires oxygen. This system has pumps and filters and requires more maintenance than the old-school system, but it's also more reliable in poorly draining soil, and is more tolerant of drainage issues or rain-saturated soil. It's also more expensive.

    Why It Matters for Your Dream Home

    If you've found the land on which you want to build your dream home and haven't yet made an offer, you can make your offer contingent upon certain results of a perc test. That way, you'll know what type of system you need before you buy the land, and maybe you can negotiate the price down a little bit to help pay for a more expensive septic system.

    Of course, if you don't end up buying the land, you'll be out the cost of the perc test (maybe a couple hundred bucks), but that's a small investment compared to the value of your dream.

    Real Life Example

    I once built a home for a family on land they bought near Norman, Oklahoma, and they hadn't done any research into the requirements for a septic system. They assumed the standard, old-school system would be fine. As it turned out, not only did they need an aerobic system, but the combination of house size, occupancy, and soil type meant they needed a system that cost almost double what they had budgeted.

    Another great source of info on what type of system might be needed on a particular piece of land (if you're in Oklahoma) is the Oklahoma Department of Environmental Quality. That is the state agency responsible for regulating waste water (among other things). They have the final say in what type of system is approved for your land, so calling them is a simple way to research the issue. Here's a link to the Oklahoma DEQ web page on septic systems.

    Researching the septic system requirement is only one component in your evaluation of land. You can read more articles on the subject of buying land here.

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