SEPTIC TANK INSTALLATION DEPTH

Discussion in 'Plumbing Code Questions' started by Jazzman, Mar 14, 2020.

  1. Jazzman

    Jazzman Member

    Joined:
    Oct 14, 2015
    Location:
    Oregon City
    Hey, can anyone tell me what the code is for setting a septic tank. I’m replacing an old steel tank with a code approved 1,000 gallon norwesco tank. There’s a layer of bedrock at about 48” so I’m not sure how much I will need to jackhammer to get tank installed properly. You can buy a riser as short as 6” high so that suggests that 6” of cover is minimum required. I’m located in central Oregon.

    Thanks!
     
  2. Reach4

    Reach4 Well-Known Member

    Joined:
    Sep 25, 2013
    Location:
    IL
    No relevant experience... I think if there were a fixed depth minimum for the top of the tank, it would be mentioned here:
    https://www.clackamas.us/septic/guideseptictankreplace.html says

    Bedding material (for example, pea gravel) is placed in the bottom of the excavation to provide a stable leveling base. The tank must be placed level from side-to-side and end-to-end. The depth of excavation must be determined before setting the tank to insure that the building sewer pipe can maintain the minimum/maximum grade set by the plumbing code once it is connected to the tank inlet fitting.
    Farther down in the document, the "Septic tank placemement [sic] for systems that were built before July of 1977" section talks of what you can do if replacing an old installation that does not conform to the newest regs.
     
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  4. LLigetfa

    LLigetfa DIYer, not in the trades

    Joined:
    Feb 6, 2011
    Occupation:
    Semi-Retired
    Location:
    NW Ontario, Canada
    Unless you have a sewage pump, the tank depth would be determined by the height of the inlet and the outlet.
     
  5. Jazzman

    Jazzman Member

    Joined:
    Oct 14, 2015
    Location:
    Oregon City
    Thanks for all of your input!
     
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