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There is a space of about 12" between my concrete drive and the house. 4" perforated PVC pipe is run the length of the house in this space and drains into the yard out back. The pipe is covered over with about 6" of clear stone. This French drain is under the eave of the house with a gutter, so very little rain water enters -- the drain is really there to deal with snow melt in the spring (I'm in Wisconsin).

At the back corner of the house I have a gutter downspout (3" by 4") that drains half the roof, about 400 sq ft. This used to dump onto a brick patio but this caused water to enter the basement and was damaging the patio. Then I diverted it onto the driveway, but this creates a sheet of ice in the winter.

Now I have connected it into the French drain. With a light rain, everything works fine. But when there's a heavy rain, the system is overwhelmed and I get water seeping through the foundation into the basement.

What options do I have to solve this problem?

Note that I am literally between a rock and a hard place here -- a 12" space between a concrete drive on one side, and the house (and then patio) on the other side. Three options I've thought of:

  1. Replace a portion of the drain where the downspout connects with solid PVC. Would this cause new problems? How far should I go in each direction?
  2. Rotate a portion of the drain where the downspout connects so that the perforations are on the top. In theory this would keep the high pressure water from the downspout from pushing out the holes in the bottom, while still allowing the French drain to collect water along it's length (though not as effectively in that section).
  3. Run two systems by digging up the 50' of French drain and running it deeper, then run the gutter drain over top of that. Obviously this would be a lot of work which I would like to avoid.

Note that view of the downspout is blocked by the gate post in this picture, but it's on the corner of the house.

Drainage picture

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  • it sounds like your yard doesn't drain fast enough. I used to get flooding in mine where downspouts emptied out onto the lawn and caused a small pond almost every rain event. A bottle of baby shampoo applied to the pond area drastically increased drainage and it hasn't pooled up since a week or two after application, despite some very heavy rains this year. Effort and cost is low, so might be worth a shot in your case...
    – dandavis
    Commented Jul 19, 2021 at 18:25

6 Answers 6

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I ended up adding a new, non-perforated pipe parallel to the French drain to carry the downspout water away. I joined the two together far from the house to minimize chances of the downspout water backing up the French drain pipe and overwhelming it.

It's been over a year, and I haven't had any more water coming into the basement. This was the last problem to solve before moving forward with insulating the basement!

Here's a picture of my solution before back-filling the clear stone. Red for French drain, blue for downspout:

Combination French drain and gutter downspout

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Putting two separate drains in the same trench is more likely to work that what you propose which is putting more water into the french drain that it can handle.

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If life gives you lemons, make lemonade.

rain barrels

http://www.gradybarrels.com/rain_barrel_photos.html

Install rain barrels as a buffer. They can capture the heavy rain and so decrease the volume your french drain needs to accomodate at any one time. You could leave one open to the french drain at a rate it can handle, or to a hose down the driveway since it is not going to freeze. Or you could accumulate the water and let it out once the rain is done.

Or use it for irrigation or washing the car. Sweet water from the sky.

I like this because you don't need to dig, and it will be fun to find uses for the water you save. Plus rain barrels are hip. Maybe you are in one of those parts of Wisconsin where people will appreciate your interest in Mother Earth and they will bring you beer and then listen while you explain about your system.

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  • 400sqft yields only 30 gallons per inch of rain, no need to go commando.
    – dandavis
    Commented Jul 19, 2021 at 18:21
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    Rainy summer evening is best time to go commando, @dandavis. Ventilation, you know.
    – Willk
    Commented Jul 19, 2021 at 22:33
  • OTOH, sweaty Midwestern humidity, @Willk... shudder
    – FreeMan
    Commented Jan 3, 2023 at 14:17
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Since your French Drain appears to be 6 inches deep, consider stacking the solid pvc pipe for the downspouts on top of it. You definitely need to not add water from roof into French drain collection system!

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I had a problem similar to yours and my fix was not an easy one. I dug a trench, about 100 feet long and 24" deep, lined with 12" of gravel, and installed a dedicated line of perforated pipe. I used SCH 35 pipe and not that cheap black stuff you buy in coils, and at the end of the pipe I had a "dry well" installed that was about 8'X 8'X 6' deep and back filled with #3 limestone. This took care of most of the rain from my roof and helped keep my basement dry. Every thing else I tried meant pools of water where I did not want them.

Hope this helps.

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Does the current downspout connect directly into the 4" PVC pipe or does it drain onto the gravel portion of the french drain?

If it is the former then cutting a hole in the 4" PVC pipe and running the downspout directly into it would help the water flow more easily into the pipe instead of potentially saturating the gravel bed at the downspout location. If flow is still too restricted, then upsizing or doubling the PVC pipe may be an option.

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