Preventing groundwater backflow through a floor drain

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    • #279395
      MasterPlumbers
      Keymaster

      We have a small building that when built they simply placed a floor drain in the basement that “goes nowhere” other than into the gravel below (it is in an area where the soil is mostly gravel). When the groundwater table is high water enters the basement through this drain. Can anyone suggest a way to prevent the backflow of groundwater through this drain?

      We are considering just permanantly plugging the drain and hoping for the best. Is that the best option?

      GP
      Cincinnati, Ohio

    • #300747
      DUNBAR

      [img]http://[/img]

      Holy Moly that is huuuuge

      You can find these at most big box stores; this picture is showing this upside down, just glue this device into the opening of the pipe leading to trap, and the ball floats on the surface of water till it raises, then seals off the opening when the water raises inside.

      You can also install a backwater valve, found at Home Depot for around $8, they cannot seem to get rid of them.

      http://img23.photobucket.com/albums/v70/DUNBAR/BACKWATERVALVES.jpg

      » This message has been edited by DUNBAR on 22 June 2004

    • #300748
      Retired plbg1

      Here we are not suppose to let storm water enter with sanitry water. Cap drin and run new pipe outside to drain storm water.

    • #300749
      PLUMBILL

      You have what we call a French Drain, was it for the drain pipe on an air condintioner?

      Just cap it, if it is not serving anything.

    • #300750
      nicktheplumber


      In reply to message posted by gpuckett:
      We have a small building that when built they simply placed a floor drain in the basement that “goes nowhere” other than into the gravel below (it is in an area where the soil is mostly gravel). When the groundwater table is high water enters the basement through this drain. Can anyone suggest a way to prevent the backflow of groundwater through this drain?

      We are considering just permanantly plugging the drain and hoping for the best. Is that the best option?

      GP
      Cincinnati, Ohio


      As I understand your question, you have a “drain” that is nothing more than a hole in your basement slab, with no actual drainpipe connected to that hole… I presume it was built there to let water spilled on the floor to drain through the hole. If so, THAT WAS A VERY BAD IDEA.

      One problem, which you’ve apparently experienced is that groudwater can come UP through the “drain.” Another problem is that if you let water drain down this hole from the basement, it will undermine the slab and the slab will subside. Your perimeter foundation may also subside eventually.

      If you want to make this hole a real drain, you will need to excavate and install a legal drain line, including a trap and connect it to the building sewer. You can also fill the hole with concrete level to the surrounding slab, but that leaves the problem of the high groundwater. Currently the hole acts as a pressure relief valve and lets the water into the basement. Groundwater pressure is a powerful force. You need to install perimeter drains to divert groundwater away from the foundation. These drains are installed underground OUTSIDE the foundation. God forbid that you have a SPRING underyour basement slab. If so, there is no practical fix, but you could make virtue of necessity and build a well under the house. One of these was featured in that movie, “The Ring.” If the water is potable, you could use it as your water supply. If it’s just water that’s unfit to drink, you could use it for irrigating your lawn and garden…

      NtP

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