Can I pave the floor of my dirt floored sump?
September 6, 2016 3:54 PM   Subscribe

I have a very wet unfinished basement. I have a sump & pump there. The sump is dirt floored, or more precisely, clay floored. It's got cement sides, but is otherwise just a hole dug into the earth beneath the basement. Can I get some sort of cement and pour it into the water such that I roughly pave the floor? I have no idea what I'm doing with this sort of thing.

The water in the sump is dirty and smelly. I believe that part of the reason for this is the clay floor.
posted by OmieWise to Home & Garden (7 answers total)
I believe that part of the reason for this is the clay floor.
Maybe, but I think only part. Water in a concrete lined sump can still get smelly. Life finds a way.

Answering a question you didn't ask (sorry), I'd suggest putting a few drops of bleach in the water when it starts to collect, and that should take care of most biological issues. It depends on where the sump drains though, you wouldn't want to be putting even lightly bleached water directly into stream.

If the sump is collecting often/always has standing water, then I think you might have problems that concrete lining can't solve.
posted by SaltySalticid at 5:27 PM on September 6, 2016

I have a feeling that the bottom of the pit was left bare in order to facilitate ground water seeping into it and getting pumped away.

Your pump is elevated off the bottom, yes?
posted by Thorzdad at 6:01 PM on September 6, 2016 [1 favorite]

Beyond the bleach suggestion, I would not try to remediate your smelly sump in any way. Certainly paving the bottom of it is not going to do any good. I would focus on ways to improve drainage around the outside of the house such that your basement becomes less wet, if that is at all possible. Check out French drains, for example. (If you are in a low-lying, flood-prone area, that's not going to be possible since there is no place for the water to go.)
posted by beagle at 6:19 PM on September 6, 2016 [3 favorites]

Are there drain pipes from the basement connected to the sides of the sump? If there are, it may be possible to block the bottom. Clay is not very porous, so it seems unlikely that the sump water seeps through the clay. Can you find a concrete paving stone that approximately fits the bottom of the sump?

There is hydraulic cement which hardens in the presence of water, although it is usually used to patch small holes in concrete. Not sure if it would work underwater.
posted by H21 at 7:13 PM on September 6, 2016

All portland cement is "hydraulic". For something like this where you just want to cover the clay and don't have any particular strength or surface concerns you could just suck up all the water with a shop vac/sponges/towels until the standing water is removed and then pour in a premix like fence post mix prepared according to instructions. Even if water seeps in it won't effect the concrete cure unless is pouring in so fast the sump pump is cycling.

However cement in the bottom of the well will not stop seepage. And if you could somehow prevent seepage it would just mean wet floors and or your floor buckling (assuming you have a concrete slab) from water pressure (IE: sealing your sump would be bad). Your sump is below floor level to mitigate water pressure on your floor.

It is acceptable to install a cover over the sump well. Though you want to make sure it allows water entry if your basement floods. You can get foam air tight covers that can mitigate a lot or all of the smell though usually they require venting.
posted by Mitheral at 7:30 PM on September 6, 2016 [2 favorites]

Sumps are often dirty and smelly!

I second the suggestion for a sump cover of some sort.
posted by ssg at 9:04 PM on September 6, 2016

Thanks, these are all good answers. The sump does have inlet from drain pipes, the floor isn't the main source of water inlet. But I think I'll go with the overall response here and not try to cement the floor.
posted by OmieWise at 5:17 AM on September 7, 2016 [1 favorite]

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