What is this? Can’t get a solid answer

We were inspecting this home the other day and found this in the basements mechanical closet. I’ve asked around and can’t get a solid answer to what this is. Anyone know? Thanks!

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Looks like a sump pit from here.


Could be part of a basement foundation drainage system. Consider this illustration and imagine it does not have a pump.


It looks like a interceptor or a separator possibly for a garage drain. Most likely a handmade sand or gravel separator.

I saw something similar in a parking deck once. It appeared to be connected to storm water floor drains. You got me thinking, maybe it was to help separate surface oils/car fluids similar to a grease trap?

What do you think the OP’s drain box is separating? Silt? Oil?

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I think it is it looks like the pipes are at a slightly different elevation. To me it appears to be a homemade sand or gravel separator. I would suspect a pipe goes from the garage to a sanitary sewer.

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Probably both, anything that ends up on the garage floor.

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In my area those were quite common on houses with in-ground basements (not walk-outs) prior to sump pumps being mandatory. The 2 main ways they were used were #1 - drain pipes around or under the foundation were routed there to cut down on foundation movements, heaving, etc and #2 - they often had a drain in the bottom going to the city sewer (that was before the municipalitys stopped allowing you to route ground water into the sewers because it overloaded them)

Or to a positive drain to the low side of the property?

Brian, I think not, because a oil/grease trap has two key features not present in the photo. It has to still the water, and it has to
provide a place for the grease to float up to for either collection or draw-off.

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