Very Shallow Sump Pump basin

Old 04-30-19, 11:35 AM
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Very Shallow Sump Pump basin

My house has a 4' crawl space for a basement, concrete floor. I live on a river and the water table is not far below the concrete pad. In the summer, fall and winter we are dry, unless there is a lot of snow and we get a freak rain storm and the the water has nowhere to drain to. In the spring when the river levels are higher the water table rises and seeps up through the small cracks in the floor and water starts to gather throughout the basement. Since flooding only started a few years back (30 years with no water ever) I do not have a sump hole, just used puddle pump(s) to suck out the surface water. I am considering a sump hole now but I am concerned that if I go too deep I will just be pumping from the water table constantly. Question is, can a sump hole be just a few inches deep? Deep enough to be the lowest point for the water table to rise to and pump out to avoid the entire basement getting wet, but not too deep that the pump is pumping all the time.
Old 04-30-19, 12:24 PM
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Welcome to the forums.

The pit can be as deep as you want. One problem with a shallow pit like you're talking about is that you can't use an automatic or float type pump in it. You'd have to use a standard pump and manually turn it on.
Old 04-30-19, 03:58 PM
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I think you're playing a loosing game. If the water table is rising that high at best you've got a bilge pump in a leaking boat. Another few years of climate change and you will be faced with real flooding. There are pumps designed to pump down to very shallow levels but I think that will only be a temporary solution.

The more permenant options are to install a deeper sump and drain pipes so you can pump down the water table around your basement, ideally a perimeter drain and while your at it apply waterproofing to the outside of the crawl space/basement walls. The other option is to encapsulate the crawl space so moisture cannot get to the house above and just let the crawl space flood.
Old 05-01-19, 11:02 AM
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A single sump pit by itself will protect only a small portion of the basement, exactly how much depends on the porosity of the soil under the floor slab.

You need a perimeter drain pipe buried in the soil (with a layer of gravel surrounding it), which can be either just outside or just inside the foundation, below floor level.

For a slab, the perimeter drain would have to be "outside", or slightly beyond the slab dimensions.

With a perimeter drain pipe system (a kind of French drain) just one sump pump pit is needed.

If you choose to put the perimeter drain pipe outside the foundation, wire brush and waterproof the foundation outside using whatever black goo is used for that purpose and let it dry before back filling.

It is important that the ground around the foundation be sloped away. Do not carve out a shallow depression against the foundation to put gravel or mulch in.

Last edited by AllanJ; 05-01-19 at 11:19 AM.

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