Locating Existing Septic Tank

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by sjsmithjr, Sep 10, 2007.

  1. sjsmithjr

    sjsmithjr Geologist

    Messages:
    295
    Location:
    Knoxville, Tennessee
    Anybody got any tips for DIY septic tank locating? I've been trying to find mine so I can check it's condition, but no luck. Here's what I've tried so far:

    1) The health department has no idea where the existing tank is located.

    2) Checked to see where the main (cast iron) DWV line exits the house. It heads towards the front of the house, then turns 22 1/2 degrees (to go around the front porch I think) just as it goes under the ground surface in the crawlspace. There's too little headroom and too many metal objects in this area to use the Schonstedt to trace the line any further in the crawlspace. I'm guessing it turns again, but I have no idea where.

    3) Scanning along the foundation and the yard in front of the house with the Schondstat I have found any number of rusty nails and other magnetic items, but no drain line or tank.

    4) There are no cleanouts at the surface on the exterior of the house.

    5) We're way under for rainfall, so the entire yard is a lovely brown. No wet spots.

    Is it time to bring the mini-hoe home for the weekend? The wife'll love that!

    Thanks,
    Sam
    Last edited: Sep 11, 2007
  2. Bob NH

    Bob NH In the Trades

    Messages:
    3,317
    Location:
    New Hampshire
    Get a sharp thin rod (maybe 1/4" diameter) and probe for it where you suspect it might be. That beats digging around with a backhoe.

    You may need something like an auger if the ground is hard. You might be able to make a drill by flattening and sharpening the end of a 3/8" rod. It is unlikely that it is more than 2 or 3 ft to the concrete top (but anything is possible). That "drill" can be powered by a standard drill (bigger is better).

    You probe pattern should be spaced to ensure that you don't miss the tank. Measure and mark to lay out your search pattern.

    After you hit something with the rod you can probe nearby to establish the size and shape of the concrete. When you get a tank-like shape at a uniform depth you have found the tank.
  3. patrick88

    patrick88 Plumber

    Messages:
    836
    Location:
    Webster Ma.
    Some tanks have metal handles on the covers so a metal detector is used by some companies to find tank covers. That is if you have one or know somebody with one
  4. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    27,242
    Location:
    Cave Creek, Arizona
    septic tank

    The metal handles will be too small and too deep for any reasonably priced metal locator to find them. A pipe locator company will send a transmitter down the pipe and mark its route to the tank.
  5. sjsmithjr

    sjsmithjr Geologist

    Messages:
    295
    Location:
    Knoxville, Tennessee
    Thanks to all for the replys. I liked Bob's idea of attaching a probe to a drill and I admit to being somewhat embarassed for not having thought of it. HJ is right about reasonably priced detectors not working at that depth to find an object that small. I was working with a Schonstedt GA-53Cx and even though it'll locate objects at 2 to 3 feet, there were just too many years worth of surface and near surface metallic debris in the yard. It's also pretty much useless for buried cast iron.

    Having no idea where the tank was and needing to locate it quickly, I called a buddy and borrowed their Metrotech 9860 utility locator. Although the use of a $3000 tool is outside the realm of DYI, it worked like a charm. Once I knew the general location and target depth, I used Bob's suggestion to quickly outline the tank. Knowing the depth was a big help; no wondering if it was a rock or the tank. Once I had the tank location outlined, I used the Schonstedt to find the handle.

    Thanks again,
    Sam
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