My house has been on the sewer main for 30+ years (original house built 1959, at least three owners ago), but a hole opened up about ten feet from my foundation. Looking down, it's a round cavity, 4 feet deep of air plus another foot of water. I was able to pull up a moon-crescent shape of a rusted metal (cover?) from the water. There are at least two narrow, old broken pipes which come into the hole from the sides. The walls of the hole are all dirt, I don't see any cement or metal walls. I tried to pound a 7 foot garden post through the water and mud but didn't hit anything hard except what seems to be mud.

Question: can I just fill it in with loose fill? Any concern 30+ years later of sewage material? Should I pump out the water first? Trying to save money and time, but do a good-enough job.

Thanks in advance

  • I'm not sure how we can answer that with no context. Is any part of that system still in service by you or others? Does it serve as a storm water handler?
    – isherwood
    Commented Sep 22, 2022 at 20:44
  • None of the septic system is in use; this find was a surprise @isherwood. We are on town sewer for decades.
    – Adammmmm
    Commented Sep 22, 2022 at 21:35
  • clean it up, seal it, use it as a mini pool :-)
    – rtaft
    Commented Sep 23, 2022 at 12:05

2 Answers 2


If this is a dry well, it is taking in heavy rain water and preventing flooding in your yard and possibly neighbor's yards as well, and filling it with dirt would not be a good idea.

You may want to mark the current water level (set your 7' post in, draw a marker line where it's wet), then go back out after a good rain storm and see if the water level is notably higher.

If it is absorbing water runoff, you might want to fill it with rock to help prevent it from collapsing completely (possibly injuring someone, definitely needing repair if that happens), but otherwise leave it so it can continue to absorb rain water.

If the water level isn't any higher after a good rainstorm, then you're probably safe in filling it in to prevent accidental collapse later.

  • 1
    I would add: find out the source end of those feed pipes! Look for gutter downspouts, sump drains in the basement, etc, and for that matter make sure your shower or laundry drains are connected only to the main waste pipe feeding the sewer outlet pipe. Commented Sep 23, 2022 at 16:36

Your description sounds like an old abandoned septic tank. If you are hooked up to the sewer this should have no use. I'm in fla. and occasionally an old septic will collapse and leave a hole. I would be ok with filling it in.

  • Thanks. What about the water? Should I pump it out first or no need @RMDman?
    – Adammmmm
    Commented Sep 22, 2022 at 22:14
  • I would put in stones first about a foot or 2 and then fil ldirt then topsoil. The water should disperse. If it is a lot ( like over 10 gallons then I would pump it out.
    – RMDman
    Commented Sep 22, 2022 at 22:40
  • Don't do anything before verifying that all observable input sources are not functional! Commented Sep 23, 2022 at 16:37

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