Drainage issue and burying downspouts

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Old 03-21-10, 04:32 PM
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Drainage issue and burying downspouts

Hi everyone,

Tried this over in the Roofing and Gutters forum, but thought I'd try here too.

I have 5 downspouts on my house that I am wanting to bury and run out to the street curb to empty as they each currently have 8' lengths of black corrugated pipe to run water away from the house and spill out into the yard. We have an area (about 25' long) between our house and the neighbor's that collects water so I'd like to put in some type of french drain system between the houses to fix this.

Ideally I'd like to run the 2 downspouts on this side of the house into this drain and end it at the street like the others, but I've heard this isn't a good idea to combine the 2 systems. There isn't much room to work with between the houses though.

Any advice on what options I have here? Should I run 2 lengths of pipe side by side with one perforated for the surface water and one solid for the downspouts? Should I keep these 2 downspouts above ground and let the french drain I install do it's job? The surface water likely won't be as bad if the 2 downspouts are channeled away underground, but I'm sure there will still be some. I'd prefer not to run either to a dry well as I'd rather just discharge it completely into the street.

Any help would be very appreciated.
 
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Old 03-21-10, 06:30 PM
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I'm actually putting in a similar french drain for one side of my house. It's slow work right now due to the cold weather (wind mainly) but also the rain and the fact that I have a bunch of old drainage line and sprinkler pipe buried that I need to excavate before I can bring in the trencher.

Anyway, on your one comment about 2 lengths of pipe...one perforated and one solid? Maybe I'm not quite understanding the situation but I don't think that would be necessary. Perforated pipe, when encased in the geotextile fabric and gravel, works fine at channeling the water to its destination. Now tying in the gutter downspouts? This depends on where those downspouts are in relation to the areas where you need to use perforated pipe. Notice I said NEED. If the downspouts run the entire length of the perforated pipe, then yes, it would probably be best to run a separate (solid) line for the downspouts to the point where your perforated pipe turns into solid. Then just use a wye to mate the two runs of pipe together.

Wherever possible I would recommend tying in the gutter downspouts directly into the drain line. I don't know if you are prone to heavy rains or not but I'm willing to bet there is the occasional heavy rain in your area. Sometimes bad drainage can lead to foundation problems you may not be immediately aware of and piping this through your drain line will help remedy and water issues. Many foundation problems are caused by water.

As for the part about running a single french drain between your home and your neighbor's, to serve both houses for drainage, I don't see why this couldn't be done. There is of course the concern that the pipe may not be able to handle the amount of water that could be draining during a heavy rain. If 2 houses are going to be using the drain line I'd recommend using a 6" pvc line as your main backbone for both houses. Drain lines tend to come in 3 common sizes: 3", 4" and 6". You could have 4" pipe serving your respective homes' drainage to both meet up to a 6" pipe that will carry both houses water to the street.

I've only got an image in my mind of what this is like based off of your description so I might have a couple of details wrong.

One last thing though you might consider. You mentioned you're using corrugated pipe for the gutter downspouts. That works fine and is generally easiest to install. But as for the pipe you are going to bury, you might consider rigid S&D pvc pipe. I decided to use this in my installation for the main reason that it might be necessary at some future point to run an auger or rooter through the line due to a clog. Corrugated pipe will not be able to hold up to that.
 
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Old 03-22-10, 07:13 PM
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Some thoughts to add...

- I would recommend staying away from the black corrugated pipe. It tends to crush over time and get easily clogged with any small sticks. PVC will hold up a lot better, and even better is the SDR (green) pipe

- Using solid PVC for the gutters ensure that you don't end up flooding another part of your property or overloading other drains. It takes more work and materials, but it's generally best to drain the gutters separately from any other drains.

- Similarly, use gravel and perforated pipe where you need to drain, then convert to solid PVC to drain out.

- Make sure that your local area allows you to drain water into the street or into storm sewers. Some areas don't allow it due to overloading sewer systems. Better to find out now than after everything is done and replanted.

Hope this helps!
 
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Old 03-23-10, 05:08 AM
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Thanks guys, I appreciate the feedback.

The corrugated is just temporary, so I do plan to use PVC for the underground.

The area that collects water between the houses is maybe 20-25' long by 7-8' wide. The houses are only about 20' apart. My thought now is to run a french drain with 4" perforated down the middle of this area, and then run a 4" solid line parallel to this (though not in the same trench) to tie my gutters into. Once I get past the area that holds water I would wye the 2 together into a solid line to the street curb.

Is it best for this line to the street be 6" then to make sure it can handle the water from both lines? Like I said, I don't think the amount of standing water will be as much if the gutters are channeled away as right now they're they empty out between the houses and are the main source of the standing water. Maybe I could get away with 4" but I should probably play it safe with 6".

I also talked to the town about this and I can basically do anything I want as long I don't damage or alter the curb.

Thanks again for your help.
 
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Old 03-23-10, 09:56 AM
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I see no reason not to run the perforated pipe and the solid pipe in the same trench. I've seen the solid pipe actually run an inch or so above the perf pipe. Doesn't really do anything other than limits the amount of digging you have to do.

Unless you get a LOT of rain, wye-ing into a 6" PVC would probably be overkill. The gravel trench will act as a buffer for those times that you get a lot of rain in a short period of time. It will "fill" with water, and drain as the water drains out. That said, you can push a lot of water through a 4" pipe.

Again, just some thoughts - I'm far from an expert...
 
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Old 03-25-10, 08:59 AM
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Thanks again for the reply Zorfdt.

Another thought, do you recommend sched 40 PVC or can I get by with the thinner wall PVC that's much cheaper? The only type of vehicle that would be driving over this area would be a commercial grade 0-turn lawnmower on occasion.
 
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Old 03-25-10, 10:28 AM
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I'm planning a drainage project, and based on my research, I'm going to be using the green SDR35 piping. It's much sturdier than the cheap PVC drain pipe, but flexes a bit to allow for freeze-thaw cycles.

I found this discussion in another forum interesting... Of course, there's no "right" answer, but some interesting thoughts:
SDR pipe vs sch 40 pipe - Page 2 - RIDGID Plumbing Forum, Woodworking Forum, Power Tool Forum
 
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Old 03-25-10, 07:38 PM
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Good info there Zorfdt. milhouse - where in the U.S. are you? The green SDR35 piping is definitely something worth considering if your winters are cold. I'm in Texas so our temperatures during the winter aren't too bad, so that's why I'm using the standard S&D pvc...that would be ASTM D2729 type pipe. Similar standards would also be D3034,D3035.

Schedule 40 pvc is more expensive than the above pvc I mentioned and I'd be willing to bet it's also more expensive than the SDR35 pipe zorfdt mentioned. Another thing about sch40 pvc is that to couple 2 pipe together you have to actually cement a coupler to both of them, whereas for the sewer/drain pipe they usually have the bell ends so you can just insert one pipe into the next one. It may not be a big deal but I find it's easier to work with.

Also the 6" pvc suggestion i mentioned earlier may in fact be overkill but in this case only you would have the best answer since you know about how much rainfall you receive and what your heavy rains are really like. You might be able to easily get away with 4" pvc.

I have a question for you though zorfdt: I have a similar issue to what milhouse has with the gutter downspouts. I have 2 downspouts that I want to tie into my line however their location would be at the point where the drain line is all perforated pvc. My only thoughts on solving this problem would be to run a separate line (solid) dedicated to those downspouts and then wye it in where the perf pvc meets the solid. To the best of my knowledge you don't want to wye in the downspouts into perf pvc, correct?
 
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