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A septic tank or seepage pit?

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  • A septic tank or seepage pit?

    hi folks - new to this forum. Maybe this is a question deep in the weeds, and this is the wrong forum – but here goes! lol

    I am using the stick test to check out the scum and sludge levels in my septic system. My second septic tank is supposed to be a 500 gallon tank but when I check the second tank I get a depth of about 88 inches. That is, the water is about 8 inches down from the bottom of the riser or top of the tank, and the depth of the water to the bottom of the tank is about 80 inches. How could a 500 gal tank have those dimensions? Someone told me the second tank might actually be a seepage pit but I don’t see how professionals could write the report below if it really was a seepage pit?

    That is, when I bought my house the professional wastewater company wrote the paragraphs below after inspection which leads me to believe the pros definitely thought it was septic tank, not a seepage pit or cesspool. The home was built in 1967. Wondering if it was some unusual kind of septic tank of poured concrete right in place? Any thoughts would surely be appreciated!

    Primary Treatment – consists of a 1,000 and a 500 gallon concrete septic tank, connected in series. Access to each tank was via a 24 inch diameter main manhole located on the center of each tank. The first tank access was at grade level. The second tank access was located approximately 12 inches below grade level. The structural integrity of the first tank and internal components, being the inlet and outlet baffles, was found to be intact from the water level up. The structural integrity of the second tank and it’s the output baffle was intact. The inlet baffle of the second tank was nonexistent and would require replacement to bring the tank to a satisfactory status. The liquid level of the second tank was approximately ¼ full. It is our opinion that both septic tanks had most likely been pumped around the time the dwelling was vacated, explaining why the tanks were found with little to no solids and a low second tank liquid level.

    Secondary Treatment – consists of a gravel seepage pit that probed to be approximately 10 feet wide and in excess of 4 feet of gravel/aggregate. Access to this component was via a 24 inch diameter concrete manhole extension and cover mounted on top of the stone, with the lid being 4 inches below the surface. Two lines were found to be entering the stone pit access. …

  • #2
    Forgot to mention those two tanks are on a hill, the second tank lower than the first. I just did a calculation that may be totally irrelevant, but if you assume the tank would be square (big if lol) and about 88 inches deep, then if it were 3 feet square then using 231 cubic inches a gallon:

    (36 x 36 x 88)/231 = very close to 500 gallons.

    Maybe that’s just a coincidence. Sure would seem a funny


    • #3
      On this subject,I feel You'll get more help on the Terry Love Plumbing Forum .Good Luck Tool
      I can build anything You want , if you draw a picture of it , on the back of a big enough check .


      • #4
        "septic tank" is a term used to define any tank which holds wastes and has some sort of bacterial action. size, shape and material have no bearing on the term. you probably do have a seepage pit in lieu of a runoff field or sand bed. They were common practices from the transitions from outhouses to septic systems, depending upon the geology of the area.

        ... it was plumbed by Ray Charles and his helper Stevie Wonder


        • #5

          Thanks guys. That is very helpful. Good forum!