High water table under our house? It's on a hill

mmzymxfNovember 16, 2012

Hi please help! We bought a house on a hill in NJ last winter. There are houses on our upper slope and also houses down slope.

During the really wet season this summer, our basement got damp, a small section even got water, like 1/8 inch deep. So we installed an interior french drain and a sump pump. After that, it's dry again, but only that the pump keeps pumping water out every 10-20 minutes.

During the Hurricane Sandy, we lost power for 12 days. This gave us a chance of stopping the sump. We saw that after 2 days, the water level in that pit was stabilized at around 10 inches below the slab surface and it has been at around that level during the last few days - maybe one inch lower but definitely not much - the pump was still submerged under the water.

Is this where the water table level is? I don't understand how come a house on a hill can still have high water table: why the water doesn't go to our neighbors property, there are plenty of them down slope..

And how do I fix this problem? If we need to dig an exterior french drain, we will have to dig really really deep - like 8 feet.

Any advice will be much appreciated!

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worthy

It's easy to have a higher water table on a hill than nearby lower land if your home is built above a "perched water table". See illustration below.

If the sump pump is keeping the water out of your basement--and even in case of a power failure--the water is still nearly a foot below your slab--what's the problem?

Other than you now realize the importance of having a backup power source in case of power failure.

Source: Wikipedia

    Bookmark   November 16, 2012 at 4:11PM
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mmzymxf

worthy, Thanks for replying. The problem now is that since we have a perched water table as you mentioned right just around 1 feet below the slab, the sump pump keeps pumping every few minutes, never stops. We do have a whole house generator so the risk of flooding our basement during rain season is not extremely high, but the pump constantly pumping is still disconcerting to us.

Is there any solution other than letting the sump pump work all the time?

    Bookmark   November 19, 2012 at 3:34PM
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worthy

In sites where there is a high-water table, it is sometimes necessary to install pumps at the perimeter of the property just to keep the excavation dry enough to pour the foundation. And the pumps then remain in place permanently.

Here's a picture of a house I built in 1989 (r) and lived in for a couple of years. To the left is a home built in 2007. Both have similar deep basements. Mine was dry as a bone; the home on the left has a sump pump that runs 24/7. (The owner also has a battery backup pump and a spare, just in case.) I also built two more homes down the same street, maybe a 20 foot lower elevation. No water problems at all.

    Bookmark   November 19, 2012 at 8:44PM
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brickeyee

"There are houses on our upper slope.."

That means YOU are not on the top of the hill.

Water from above you drains down (damn that Isaac Newton and his gravity).

Unless you can show that someone above you diverted water and caused your problem, you have to fix it (you have to accept 'natural runoff from above you)

If it is surface runoff you can instal french drains, but watch out what YOU do with the water you collect.

The folks below you will NOT be happy (and can come after you) if you divert it onto their property.

This post was edited by brickeyee on Tue, Dec 4, 12 at 15:29

    Bookmark   November 22, 2012 at 3:24PM
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jasper60103

I feel your pain. My last house was on a high water table. This was a new construction and we lived there for 9 years. The sump pump ran every hour, including winter months and summer droughts. I could literally watch the water level rise in the sump pit. The sump pump failed after sevens years. Fortunately, it failed on, i.e. it would run-on and not shut off automatically. I replaced it. We moved a couple years later.

As noted in previous posts, not much you can do about it, except have a good backup pump.

    Bookmark   November 26, 2012 at 3:38PM
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