drain tile

Old 06-23-03, 09:37 AM
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drain tile

We are installing drain tile and my husband has trenches built around the basement, and will install gravel and pipes. Does any one know how deep these trenches have to be dug? Were hitting water now and I'm afraid were just digging what amounts to a well in the basement floor. Thanks.
Old 06-23-03, 10:51 AM
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Well, if your using 4" perforated drain pipe with an inch of pea gravel above and below the pipe you would need a 6" trench minimum, where are you draining the water, basement drain or a sump pit? How deep has your husband dug so far?
Old 06-23-03, 11:17 AM
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The best way of keeping water away from a foundation is to divert downspouts away from the house, and slope the ground away from the house. In that way any rain, snow melt, etc. will not drain down into the soil near the foundation. For any water that does drain down into the soil near the foundation, and also for any excessive ground water already in the soil from a high water table, a perimeter drain tile and stone or gravel backfill has been the standard approach. This is a waterproofing system. The same application is done to the "interior" of the lower level and this works extremely well especially in older homers when exterior applications cannot be done.
When water gets into such a gravel backfill, it quickly runs down into the drain tile and is diverted away through a pipe either by gravity or a sump pump. When a drain tile is used, but soil is used for backfill, the water can't drain away as quickly, so it tries to drain through the foundation wall. If enough water is present, hydrostatic pressure will force it through any opening it can find in the foundation wall, no matter how small.
The purpose of the stone or gravel backfill is to relieve the hydrostatic pressure. With the correct backfill material, the liquid water will travel the path of least resistance: through the backfill into the drain tile, rather than through the foundation wall. I will point out that drain tile comes in two styles - rigid and flexible. The rigid has a slot on one side and this is installed with slot down. The flexible has slots on 4 or 6 sides, if you will but this should be installed with a silt sock over it. Costs more but prevents silt from getting into the pipe. Most homes, for interior applications use the flexible but either is acceptable.
When the soil is merely damp, as it often is, water isn't the problem. When damp soil is next to a foundation, it will cause the foundation to get damp. The dampness will work its way through the foundation wall and eventually enter the basement or crawl space. Concrete and masonry are actually very porous, so dampness can move through such materials fairly easily. (This is done through a process called capillary action.) Once the dampness reaches the interior surface, it can evaporate into the basement or crawl space, increasing the moisture in the air.
To stop the dampness is relatively easy because, by not being in liquid form, there is no hydrostatic pressure. A simple foundation coating will do the job. This coating is called dampproofing. It isn't a substitute for waterproofing.

PROCESS: Remove about 16" space out from wall. Ensure that you are about 8 inches out from footing. Dig a trench along the footing that slopes gradually towards a sump basin. Trench approaches the sump basin from two sides. Drill " holes into each of the block cavities (2 per block) in the course of blocks that sits directly on top of the footing. Water now comes out of these holes when it rains. Place 4" corrugated drain pipe in the trench and run this all along the trench to the sump basket. You may use a silt cover or a silt sock which covers this pipe of which then you would place 3/4" pea gravel over this to a level that leaves about 4" of space for your new concrete. Place the concrete all the way to wall - NO SPACE IS REQUIRED. Install a good sump pump and PVC piping - 1 1/2" out to the exterior and away from the homw for proper drainage. This could be buried and run into a drywell at least 20 plus feet away from the home on down grade.

Hope this helps!

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