French Drain Pointers


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Old 03-21-23, 06:21 PM
J
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French Drain Pointers

I'm thinking of putting in french drains around the perimeter of the house and have some basic questions. This would be my first time attempting a drainage project so I welcome tips and suggestions from the experts. My yard is very flat and all the research I have done so far tells me I need to dig a trench that's 18" to 2' deep. That's fine but if I need to maintain a 1% slope at that depth and try to daylight it near the sidewalk (or even just far enough away from the house), I would still be underground by a decent amount. I haven't done accurate measurements of the grade from the back/side of the home to the front but I suspect it's not that much.

I can put a popup emitter or a termination distribution box at the end but it would be under ground level. Is there a better idea to let the discharge end see daylight without being so deep?

If a dbox or emitter is the only option, is there a problem with the portion of the water that can't be discharged remaining in the pipe (the solid section away from the house)? Aside from mosquitos, etc. any other issues to be aware of?

Another idea I heard was introducing a large catch basin in the middle and using a sump pump to push the water to the solid pipe that starts more elevated. This way I can better control the height at which the water exits at the sidewalk.

Any help appreciated!
 
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Old 03-22-23, 01:34 AM
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For a french drain gravity is your friend and you want it as simple as possible.

Only french drain I had was a backyard that was dug into a hill such that rain would pour down, that drain was only about 9" deep at the high point (just a few inches below the surface) and around 16" at the deep end where it just exited into the wooded area in the front yard.

Trench, corrugated pipe, covered with pea gravel, covered with dirt. worked great1
 
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Old 03-22-23, 05:00 AM
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Because the drain usually gets installed at the bottom of your foundation wall and above the footer, you cannot slope it. The portion around the house's perimeter is basically horizontal. Depending on your house's construction, mainly if you have a basement, you might be able to slope the drain around the house but you have to understand that there will be greatly reduced water protection below the drain line.

Do NOT use a pop up emitter. They clog. And, pop up emitters really only work with high flow volume like you might get from downspouts after a heavy rain. The water entering the French drain will be a more constant trickle. That low flow rate means sediment & dirt can't rise up and out a pop up and will setting in the pipe, eventually clogging it.
 
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Old 03-22-23, 11:04 AM
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Marq1 So did your drain perform well even at 9" of depth? I was thinking I would need to start more shallow at the start of the french drain so that I can create the slope needed to terminate it on the street at a decent enough level. Curious to know.
 
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Old 03-22-23, 11:12 AM
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Mine had a gentle "V" slope to the center of the yard and excess water would migrate to the bottom then down to the drain.

9" ditch, 4" corrugated pipe covered with some pea gravel so it's only a few inches of dirt.

In the heat of the summer that area of shallow pipe would brown a little since it worked too good to move the water away!
 
 

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