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  1. #1
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    Jun 2012
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    Default French Drain to Dry Well

    I posted a month ago about installing a French Drain. Bit the bullet and dug all the way down to the footer...about 6 feet. Dug down an additional foot+ below the top of the footer to install the drain pipe. It travels the entire length of the front of the house and wraps around the side. On the side of the house I am installing two basement windows. This required digging out window wells about 4 feet deep. I will install drainage grates and stone in the bottom of these that will tie into the French Drain pipe. Since the French Drain runs by these two window wells the trench has been dug all the way down to the footer...I'll back fill to build up to the planned depth of the window wells. The soil at the level of the footer is a sand/gravel mix...it extends out well over 4 feet from the house. The entire area is composed of this material (Sand/rock/clay mix). You can dig it out with your hands.

    If I run the drain pipe for the french drain all the way out from the house at the correct angle to maintain water flow it will have to travel well over 125 feet until it breaks above ground. The back yard slopes gently away.

    Question: Since the ground below the footer is a sandy mix and water drains incredibly well, can I install a dry well next to the house? The top of the dry well will be a foot below the top of the footer and buried below about 2-3 feet of additional crushed stone. It will essentially be at the bottom outside edge of one of the window wells, about 4-5 feet out from the footer.

  2. #2
    Join Date
    Aug 2008
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    69

    Default Re: French Drain to Dry Well

    Congratulations on all the heavy work you have done to complete this project; I'm sure it will provide the results you hope for; standard practice calls for installing the dry well at least 10' away from the building; the only alternative I can think of is to leave the excavation the way it is for a while & wait for a good soaking rain (as a perc test) to see if there are any problems; another perc test might be to flood the excavation with a hose for several hours and check for leaks. Good luck, whatever you decide.

    I didn't read your original post, but I assume that you were getting water inside the basement & that's the reason you put in the french drain tiles in the first place-----this should indicate to you that you have to go at least 10' away from the building with the dry well.
    Last edited by von_steuben; 07-12-2012 at 04:22 PM.

  3. #3
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    Jun 2012
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    7

    Default Re: French Drain to Dry Well

    Von-Steuben,

    Thanks for the reply. The ground was so easy to dig in the trench that I just dug out a trench to accommodate the the drain pipe and will be able to use a walk behind trencher to extend out the rest of the way.

    The problem I was having is that water drained down hill, hit the side of the house and soaked through the block wall and between the base of the block wall and the footer. The wall was never sealed. I sealed it with a rubber coating and lined it with plastic. It's been a chore, but the basement will finally be dry!

  4. #4
    Join Date
    Aug 2008
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    69

    Default Re: French Drain to Dry Well

    Geneticswhiz:

    After going back to read your previous posts, and those of Houston Remodeler, I would tend to agree with the ideas that you and H.R. put forward-----namely, that the central water problem in your case is that the rain water is flowing downhill for quite a number of feet at the FRONT of your house, & the water is building up considerable pressure as it hits your front foundation & causing water in the basement; you say that "there is 6" of topsoil and the rest is clay", & that you think the water is flowing along the top of the clay, hitting your foundation, then flowing down to the footing & entering the cellar; however. you should have a more accurate view of this now that you have excavated down to the footing---there's a good chance that the clay may only be several feet deep and the "loose fill at the bottom at the footing that you can remove with your hands" is a lower layer of porous loose soil that is conducting most of the subsoil pressurized water coming down the hill toward your house.

    In such a case, I doubt that a dry well dug down lower at the footing would do much good in diverting & removing the water away from your foundation----you would be much better off trying to divert the subsoil water coming down the hill by using Houston Remodeler's idea, which could be called a "curtain drain".

    A curtain drain is a well-known tactic to intercept the subsoil water moving down the hill, and diverting it via 4" perforated drainpipe (SDR-35) around both sides of the house foundation, and down to the opposite side of the house, which is at a lower grade, to an exit point where it is discharged harmlessly away from the foundation----see the excellent article below by Eric Nelson (requires Adobe reader on your system) to learn the details of how this system is designed; also Google "curtain drain design", and "images for curtain drain design".

    Notice in the Nelson article that these drains are located a number of feet toward the FRONT AND SIDES of the house, several feet down, and backfilled ALL THE WAY TO THE SURFACE with 3/4" crushed stone---the strategy, again, is to INTERCEPT the water as it flows downhill toward your house, and DIVERT it via the drainpipe and crushed stone, around the sides of the house, and down to a gravity flow discharge point at a lower level; note also that the roof gutters are tied into this system via separate solid drainpipe in the same trench; and that fabric filter is used to filter fine soil particles so they don't clog the perforated drain pipe with silt; and that CLEANOUTS are installed at the corners so the drain can be cleaned out in the event of clogging.

    Installing an elaborate curtain drain as Nelson describes would require considerably more trenching & materials; since you have already excavated down to the footing at the foundation, your best bet is probably to go with what you have now & see if that will work for you-----extend the french drains around to the window well area, which you have already done, and trench out the 125' to a lower location at the rear of your property for a discharge pipe at least 4" SDR-35 or perhaps a 6" discharge SDR-35 drain for the 125'---this should dramatically reduce the water pressure building up at the base of the front of the foundation, and hopefully will be the solution to your problem.

    While you have the trench around the front/side of the house open, you should be "doing perc tests" with your garden hose---pour as many gallons of water as you can to the footings with the hose & see how long it takes for the water to disappear into the soil around the footings----if you have standing water at the footings for a period of time, then a dry well won't do you any good at the base of the footings----you can try to build a dry well 10' or more distance from the footings & flood the area again with the garden hose & see how THAT works----but you have to remember that any dry well has a LIMITED GALLON CAPACITY, and once met, the water will once again back up towards the foundation & into the cellar.

    If you want to try a dry well, at least dig one that's "downstream" of the problem towards the REAR of the house, at a lower level in a layer of soil that is absent or below any clay deposits, so that the water has a chance to drain into the sub-soil.

    The 125' discharge drain option has none of the limitations associated with dry wells----the water will continue to flow harmlessly out the discharge point without any backing up; observe Nelson's advise & contact the natural gas, electric, & water supply co.s for utility locations if you do any extensive excavations for this or something like a curtain drain.

    You can always go back at a later date to install a more elaborate curtain drain along the lines of the Nelson model if your present efforts don't solve the problem; I think that you will eventually be successful, and you will end up saving thousands if not tens of thousands of $$$ on this project---a unique aspect of drain projects for yards is that the materials like drain pipe, crushed stone, filter fabric, etc., are very low cost; the biggest part of the project is the digging.



    http://www.finehomebuilding.com/PDF/Free/021189052.pdf
    Last edited by von_steuben; 07-13-2012 at 04:27 PM.

  5. #5
    Join Date
    Jun 2012
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    7

    Default Re: French Drain to Dry Well

    von-steuben,

    Thanks for the information...yes, a curtain drain 4-6' out from the house would probably have been the ideal fix, but with a coat of rubber and a sheet of plastic over the block foundation I doubt anything will get to the block wall.

    After thinking on it I figured that if I'm going to the trouble of all this excavating I might as well just do the little extra and trench all the way out away from the house. Why do everything I am doing just to dump the water right next to the house. Now it will be far, far away and should not be a problem any longer.

  6. #6
    Join Date
    Aug 2007
    Posts
    612

    Default Re: French Drain to Dry Well

    Congrats on all the hard work...I can relate as I had a similar project about 15 years ago. The back wall where I dug out is now the driest basement wall we have!

    Running the drain to daylight is the optimal solution if you have the property space to get the needed pitch from that depth. I was not able to do that but had to dig a dry well about 10' from the house lower than the drain tile at the foundation. I then installed a pump that pumps the water out and down to our drainage ditch in front of the house. The only problem is if we lose electricity and I need to hook up the generator to keep that pump and the inside sump pump running.

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