I have a few questions regarding my downspouts and french drains. I had previously installed one with the black corrugated pipe. Ran solid version down to a gravel pit and then used perforated kind with a cap on the end. Well in heavy rains I noticed it backing out of the downspout connection. So I am digging it up and redoing it.

So far my plan is to correct my mistake and use solid sch40 pipe to the pit, then use the kind with holes. I am still in the process of digging up the old one but have a few questions.

1. Frost Line. I live in St Louis. Supposedly it gets cold and snows. Sometimes it does. Grew up in MN and these folks don't know snow. But as it gets below freezing is the frost line something I need to worry about. If the pipe has the correct grade in theory it will not have any water in it to freeze and crack. My soil is clay pretty much if that matters.

2. Do I need to put landscaping fabric and rock around the solid pipe or can it lay in bare earth? I will make sure it is flat and does not have any gaps under it.

3. I don't remember how deep the rock in the pit was, but using the perforated sch 40 do I need to wrap it with landscaping cloth and how deep should the gravel be below and above the pipe?

Luckily this drain has a little slope so that is helpful, but I have two drains after this so I want to figure out the correct way to do it. By the time I am done, my arms should be huge

Thanks for any help.

 

Why did you cap the end of the pipe? That might have been your problem.

 

I am pretty sure I capped it, was about two years ago when I put it in. It was a black cap with a bunch of holes it in. Mainly a plug to keep things out but still drain. While digging today I managed to get some of the current black corrugated pipe exposed. It does not look like it stayed level which could be part of the issue as well. I figure the slope did not stay the way it was put in. Part of the reason I am redoing the whole thing.

 

Perforated pipe (especially the corrugated type) and gutters are not a good combination.

Since rains can be heavy and they are shed of the roof and into the gutters. Because of this the fast moving water will pick up and carry a lot of debris - dirt, roofing granules, leaves, acorns and whatever. This debris gets in the slits/holes, plugging them and sand/rock and can eventually eliminate water flow out of the pipe.

The only thing worse is looking a downspout system into drainage pipe that carries water from a basement water control system.

Dick

 

It is quite possible to perforated pipe is clogged, digging that section up today hopefully. I guess I should mention that I have gutter guards on all my gutters as well as a mesh screen covering the input into the downspout from the gutter. I have maple trees and used to get clogged up but now no issues. I have not found any debris in the underground portion of the pipe yet. So I think putting in the smooth PVC will help. Just need to figure out those couple answers and I should be in business.

 

You indicated that you don't recall how large the "gravel pit" (dywell) is, nor did you say how many downspouts empty into this drain, nor how many square feet of roof that covers, but you may simply be dealing with more water than you realize. You will need to do the math, based on the involved area of your roof, but consider that for just 100 square feet of roof, 10' by 10', a half inch of rain, which I would say is somewhat average, is equal to 31 gallons of water. (231 cubic inches ger gallon) Multiply that by the actual affected area, and it can easily run into hundreds of gallons. For this reason, depending on the topography and other factors around a home, the best solution is generally to drain to daylight, as opposed to a drywell.

 

I thought about that fact I may be getting too much water. There is only one downspout draining in to this. Not sure the square footage of the roof though. I have almost completely excavated the entire buried portion. I can see a few humps where the ground settled. I am fairly certain this is part if not all of the problem. Basically I did it wrong the first time around. So I am going to start over and do it right.

I do not have the option to drain to daylight either. I live on a corner and I have a huge amount of utilities in the portion of my yard that is near the sidewalk. I really don't want to have to deal with that. But I can not drill in the curb either. So I opted to disperse it underground. I probably did not make the pit large enough as which is why I have asked the questions. Rather get it right this time.

I have a fourth question. I am needing some mudjacking done on the sidewalk as well as my garage. The drain pipe will run under the sidewalk. I talked with the mudjacking guy and he said sch 40 should be fine under the walk. I expect it to be 18-24 inches anyway. Should I do anything special in this section? Put rock all around the pipe or something. Hate to finish the drain and have it crushed by the mudjackers. If anyone has any thoughts on this or the original three questions it would be appreciated.

 

As far as I know the answers to the first 3 questions are no, no & no.

 

I would use a filter sock on black corrugated pipe or the PVC with holes.
About 6 years ago my French drain clogged up I started digging at the end found 8 foot section of 4 inch PVC with holes completely clogged. They had maybe 1-2 inches of gravel all around the pipe then about 1 foot wide plastic covered by the top soil and grass. The end of the pipe emptied into about a bag of gravel covered soil & grass. Well I replaced that section of pipe black corrugated added more gravel covered it up. It was winter had to get something done and just wasn't educated enough about it. 5 years later its almost all the way clogged I am getting ready to re-do it and make it better and right.
Moral of story at least use the filter sock

 

I actually finished it up today. I did put some fabric around the perforated pipe. The old black corrugated one was all plugged up by tree roots. I did not have enough rock or any fabric on that one. Completely wrong. This one has fabric lining the pit. about 8-9 inches of rock, then the new pipe and about 8 inches of rock on top. Hoping with gutter guards and screen on the downspout intake I should be clog free until I can sell the house lol. Luck for me I have two more downspouts to do.