Do I need to install drainage medium for my sump pump to work well in an old basement?

Question

My house is old. Built in 1922. I have installed a sump pump. When we get heavy rains like right now it leaks pretty good. I am in Kansas City and my soil is very clay like. The lowest point in the floor of the basement is original so it is a thin layer of cement on the clay (no gravel). It buckled last year and now water pours in (that's where I put the sump pump). But water is still coming in along the cracks and floor, so its like the sump isn't doing exactly what it should be doing. It is pumping water out that if I didn't have it would be flooding the basement. The pump is in a pit embedded in the ground, plugged in and plumbed outside.

Should I tear out the floor around the pit, dig down 6 inches, lay 2-3 inches of gravel then lay a new slab on top? I think the water just can make its way through all the clay to get to the sump pit.

Answer 1

Sump pumps can't do their job effectively without a suitable route for water to reach the pail. You don't have that. You may not need to remove the entire slab, though. It's possible that evacuation routes around the perimeter would do the job. It's hard to say with the small window into the problem we have.

Note that it's not "gravel" that you'd install--it's washed rock and possibly drain tile (perforated, corrugated plastic pipe), which may have a fabric sleeve over it. If you're going to all the effort and expense, be sure you have a solid plan.

Answer 2

I'm also in a 1920's era home in Kansas City, sitting on heavy clay soil, so your issue sounds very familiar. My soil is so dense that, like you suggested, water can't perc through it in places. Some spots in my garden are so dense that I can dig a hole 2 ft down and 2 ft across, fill it with water, and the water will evaporate before it drains.

It sounds like you're getting groundwater seeping in and coming up through cracks in the basement floor, rather than going through the soil under the floor. A gravel layer near and around the pit can help but to truly fix it you'll need to trench around either the perimeter of the basement floor and install drain pipes going into a sump pit, or around the outside of the house and install a French drain or drain into the sump.

Check the ground slope around your house. It should slope away from the foundation to at least 4 ft out, farther if possible, to keep ground runoff and downspout drainage away from the structure.

Do you get seepage through the basement walls? If so, only trenching around the outside of the house and putting in a drain system there will keep your basement dry. (My parents have 7 springs 4 ft up on their basement wall that run every time we have heavy rain. They just elevated everything off the floor and let the water run into the floor drain because the external drain system would be too expensive.)