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Re: French drain installation

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Good point!
A "french drain" is not a "back drain" or wall drain.

Steven A.
Los Angeles

"Sprague, Harold O." wrote:

> Desi,
> I am a little confused.  Are you installing a French drain or just providing
> a continuous perimeter wall drain?
>
> There is no standard of care, but I can offer what I have done in the past
> for a continuous perimeter wall drain.
> I provide filter fabric in the base of the excavation and use 3/8" open
> graded clean crushed rock at the base lay the pipe at (1/4" ideal 1/8" after
> the war) per foot.  I use enough filter fabric to wrap all of the crushed
> rock.  After the pipe is placed I back fill with more crushed rock to
> provide a minimum of 12" of rock around the pipe.  I then finish wrapping
> the crushed rock in filter fabric and lap the fabric over the crushed rock.
> This wraps the entire crushed rock in filer fabric.  If you just wrap the
> pipe, the filter fabric has much less surface area and will seal with fines
> rather quickly.
>
> If you are indeed considering a French drain, you should run your perimeter
> wall drain to the French drain.  The size of the French drain and location
> will depend on the water table and the percolation rate of the soil.  I
> would avoid making the perimeter wall drain the French drain. You will wind
> up with a pool of water along your wall.
>
> If indeed you have a retaining wall, just run your continuous wall drain to
> weeps placed at about 10' centers.
>
> Regards,
> Harold O. Sprague
>
> -----Original Message-----
> From: djkiss55(--nospam--at)juno.com [mailto:djkiss55(--nospam--at)juno.com]
> Sent: Monday, July 07, 2003 1:13 PM
> To: seaint(--nospam--at)seaint.org
> Subject: French drain installation
>
> Any response to these issues is gratly appreciated.
>
> What is the standard of care for installing a 4" dia. french drain along a
> 70 foot-long by 9 foot high masonry retaining wall? Are there any gravel or
> crushed rock specific requirements? What is the minimum slope required by
> the standard of care? Is a 1/4" slope appropriate?
>
> Thank you in advance.
>
> Desi J. Kiss, MS, PE
> Phone: 949/458-9169
> E-mail: djkiss55(--nospam--at)juno.com
>
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