I have a septic tank in my yard that is no longer used. Can I leave it there? Should I remove it? Fill it with something? I'm not entirely sure of the building material used to construct it; I assume whatever was the customary materials in the pacific NW in the mid to late 50's.

  • Yep. Be wary of any asbestos hazards in old cement tanks as well.
    – WOPR
    Commented Jan 10, 2011 at 0:03
  • 1
    In ground pool.
    – Freiheit
    Commented Jan 10, 2011 at 14:13
  • 1
    Don't leave it lying around else someone mistake it for an atomic bomb (source: youtube.com/watch?v=0F324755_oA)
    – JohnFx
    Commented Jan 10, 2011 at 15:52
  • Would there be asbestos in a septic tank!?
    – DA01
    Commented May 15, 2013 at 18:23
  • How about a Koi pond...?
    – Lee Sam
    Commented May 12, 2017 at 3:33

3 Answers 3


You'll have to check codes, but I believe the usual procedure is to fill them with something like sand - since it's a septic tank, and since (I presume) you had it emptied before leaving it to rot, you probably don't need to clean it, just get it filled.

You can NOT just leave it there - eventually it will rot away and collapse, presenting a hazard at some unknown future time.

You might call around to the local septic companies and ask them what the usual procedure is in your area, they should know who can handle the fill-in of the tank properly.

  • 3
    Many years ago while I was inspecting a lake front cottage, I actually had my leg break through the thin ground covering an abandoned old school wood septic pit. No injury, but what a surprise! Commented Jan 8, 2011 at 12:54

Standard procedure in this area is to crush steel, wood or plastic ones and fill the hole, and to fill concrete ones with stone. In all cases pumping the waste first.

A common reason that has not been mentioned yet is to prevent people from entering the old tank - there are NUMEROUS tales of using the old tank as a place to put grass clippings, kid drops the rake in the hole, goes in after it, asphyxiates, etc...the top search result is this one where the kid lives and 3 rescue workers died, while a 4th was injured.


an unwanted unused septic tank can be made into an excellent root cellar. Some people will pay good money for one for this purpose if they have the room on their property.

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