[joeygoet]

Would like to know the experts' methods for the following: 3 downspouts on same side of house each routed underground-grade has 6" drop for every 10'

My questions:

1. 4" perf corrugated or 4" solid corrugated or or PVC with the holes?

2. Connect all three, or drain separately

3. How deep?

4. Line with fabric, install washed stone and pipe?

5. Exit above ground? If so, how do I end the pipe?

6. Keep below ground? Again, how do I end the pipe?

Thanks for all the input. I enjoy the forum.

[Forge]

Your choices depend highly on where this water is going to be going...

[Pelican]

How far will the pipe run? Will it be daylighted? What's the total square footage of roof feeding the three pipes? Do you have access to a storm drain?

[Lanelle]

I usually use solid pipe so no gravel needed.
PVC is more expensive than flex but is easier to clean out and is stronger.
Your site will determine exactly how to do this project.
I like to take the water away from the house and use a pop-up drain to allow the water to disperse at the exit.
As others have said, your site and roof factors will determine the best solution.

[joeygoet]

Thanks for the replies. I value all the input.

Pelican: you asked about the length of pipe run, and whether or not it will be daylighted. I don't know-hopefully you can tell me.

The house is approx 40 ft from the road, the three downspouts would support 1/3 of the roof's water, and there's no storm drain to access. Grade drops 6" for every 10 ft. This is new construction-no landscaping. I obviously would like to send the water downhill toward the road.

Let me know how you would tackle this. Hopefully I've provided enough information.

[phototropic1]

To correctly size your pipe, you'll need some good data on rainfall amounts for your area. You can get this from NRCS and possibly from US Geologic Society, extension service, or a meteorological service. And you'll need to calculate the surface area of the roof being drained. But, based on no conrete rainfall info, 4" sounds a little small to me. I would bump that up to 6". But, do the math on that one and you won't have to sweat it.
As far as perforated or solid, definitely solid. A French drain is for dealing with water that is already in the soil profile. You certainly don't want to be run a bunch of water from the gutters through a French drain. You would be fighting an uphill battle if everytime it rained, you were dispersing water throughout the same soil that you were trying to keep dry. I personally like PVC over corrugated, but if you do go with corrugated definitely get double walled. That single walled stuff is flimsy, flimsy, flimsy.
I would also recommend having several catch basins along this pipe in order to clean out any debris. I like to put them at the junction of the main pipe and the spur pipes leading to each downspout.
As far as where to daylight your pipe, it's hard to say without knowing the topography of the site.
I'm sure others will chime in on this.

[HRLand]

Are you sure you're allowed to dump it in the street? Most cities around here require you to install seepage pits.

[joeygoet]

I don't want to 'dump' in the street, just send toward the street.

Phototropic1: I agree with the information you provided. My plan at this point is to send 3 individual perf corrugated lines about 25 ft downhill toward the street.

My final question would be how to end the 3 lines. With a drain box, below grade end cap, above ground exit??

Thanks for all the help.

[agla]

1. 4" perf corrugated or 4" solid corrugated or or PVC with the holes?

Corugated is easier, but easier is not always better. The advantage pvc has is that it is rigid and smooth, so you can set an even pitch whether it is perf or solid. That means the water will move at a constant speed. Suspended material (silt or clay) falls out of solution when the water slows down.

Think about that corrugated pipe. It follows the contour of your trench and easily adapts to any areas that may settle. That sometimes makes low areas that hold water, but always means there are slower flows in portions of the pipe. Add the ribbing to that and you have a much greater chance of silt and clay build up in the pipe.

That does not mean it is a crime to use corrugated, just that you need to think about the situation and make good decisions.

Use solid where you don't want to introduce water to the soil (like within 10' of the basement) and perforated pipe in a stone lined trench where you can lose water. Remember that volume of water is the problem and anywhere in the system you can reduce that volume reasonably, you should.

2. Connect all three, or drain separately

Volume of water is the problem. You can deal with it as three smaller problems or one bigger problem. You may need a bigger pipe size if you combine. It also depends on where you are going with the water and whether the destination can handle all of that water at once whether it is a leachpit or daylight.

3. How deep?
You will need 6" minimum cover in a lawn area, but the depth is more likely to be determined by the pitch of the pipe and the destination to some extent.

4. Line with fabric, install washed stone and pipe?

This would only apply to peforated pipe. You would not want to line the bottom of the trench with fabric because it would slow down the infiltration rate and silt or clay could build up on top of it sealing the water from going through it. It would be good to line the sides of the trench if your soil is likely to migrate into the stone. You definitely want to cover the top of the stone so the soil over the trence does not migrate into the voids between the stones.

5. Exit above ground? If so, how do I end the pipe?

If you have an area that will accept the amount of water you are dealing with, you could daylight the pipe. Keep in mind the amount of water and the speed that it will be coming out with. Sometimes you need to have larger rocks all around the end to dissipate the energy of the water so it does not erode.

I it is a good idea t have some kind of barrier to keep critters out. Depending on how visible the pipe is, they sell angled pvc grates, for lack of a better word, that cap the end, keep out critters, and fit a slope better.

6. Keep below ground? Again, how do I end the pipe?

Your pitch on the pipe will be one determinator. The other is the destination. The leachpit or dry well might stick up higher that the pipe, so you want to plan for that and for soil cover if it is in a lawn area.