Question about pitch of underground drainage pipe
Question about pitch of underground drainage pipe
(OP)
I hired a contractor to fix some water issues in our backyard. We're on a hill and he went about 120 ft around two sides of our house with this drainage pipe. It's the perforated black piping, tied into our down spouts of our gutters, with a pop top at the end of the pipe to keep rodents out. It has some reservoirs with covers in it for cleanup of debris.
My problem with it was I was under the impression it needed a constant pitch of 1/4 inch a foot or more for proper water drainage. I know that is not the case and in some places may actually go uphill, but at the end is the low point and all the water drains out that end. I'm guessing some water is remaining in the piping. He said it's not a concern, and that no bugs or anything will reside in it. Then I got to thinking about water possibly freezing (we're in MN), or trees or something starting to grow in it (we have maple trees with the helicopters). Any thoughts? Am I just being paranoid?
My problem with it was I was under the impression it needed a constant pitch of 1/4 inch a foot or more for proper water drainage. I know that is not the case and in some places may actually go uphill, but at the end is the low point and all the water drains out that end. I'm guessing some water is remaining in the piping. He said it's not a concern, and that no bugs or anything will reside in it. Then I got to thinking about water possibly freezing (we're in MN), or trees or something starting to grow in it (we have maple trees with the helicopters). Any thoughts? Am I just being paranoid?





RE: Question about pitch of underground drainage pipe
It's likely just fine.
f-d
¡papá gordo ain't no madre flaca!
RE: Question about pitch of underground drainage pipe
RE: Question about pitch of underground drainage pipe
I would agree that a slope of at least 1/4" per foot would give proper drainage, however my guess is that your pipes will be fine even if it freezes. Unless the pipe is standing full of water, there will be space above the water for it to expand as it freezes so the pipes shouldn't burst. Again, your situation is not ideal, but I would wager that it will function OK.
The thing that I would watch out for is that a large amount of ice will reduce the capacity of the drain pipe - so if you have a large roof area going into the pipe and the pipe is half full of ice, then the rain water could back up and leak out where the downspout is connected to the undergound pipe. This could be a problem if a large amount of water leaks out near your house and finds its way into the basement.
Ben
PS. I doubt that trees will grow in it since they won't have any sunlight.
RE: Question about pitch of underground drainage pipe
BUT ice could be a problem - sudden warm up causing ice/snow melt off the roof.
Ask him to guarantee it for five years and see what happens.
RE: Question about pitch of underground drainage pipe
RE: Question about pitch of underground drainage pipe
f-d
¡papá gordo ain't no madre flaca!
RE: Question about pitch of underground drainage pipe
RE: Question about pitch of underground drainage pipe
The big 120 ft drain with 3 gutter spouts in it remains almost flat (maybe 4-6 inches of downward pitch - tops) for the first 85 ft or so. The last section is where it starts to pitch downward (another foot or so). I can't tell exactly how it flows (it was covered before I saw the complete layout), but it may rise a couple inches in a few long stretches is my best guess. It's about a foot under the ground across the whole section.
The termination point is actually a popup that jumps vertically up and the water comes out the top. So at a minimum, water at least resides by the popup. It could have been dug 5 ft farther to come out the side of the hill (where the steep incline is, and we could have made up the pitch from the flat ground). A shorter drain he put in the front I poured a couple gallons of water in last week and nothing came out. It's got a similar slope/popup on a smaller scale. It's shaped similarly to an elongated fishing hook, when taking the gutter attachment into account.
RE: Question about pitch of underground drainage pipe
RE: Question about pitch of underground drainage pipe
RE: Question about pitch of underground drainage pipe
Richard A. Cornelius, P.E.
WWW.amlinereast.com
RE: Question about pitch of underground drainage pipe
**
Are you saying the pipe has a 90 degree bend, and comes up out of the ground, and that's the low point where the pipe discharges?
If so, then your pipe is probably mostly full of water most of the time, and is going to burst in about 6 months, knowing Minnesota.
Hydrology, Drainage Analysis, Flood Studies, and Complex Stormwater Litigation for Atlanta and the South East - http://www.campbellcivil.com