Advice for underground downspout drain


Old 11-09-05, 09:59 PM
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Advice for underground downspout drain

Hello all,

I will be installing an underground downspout drain soon and need some information. It will drain 2 of the 5 gutters on the house and will run parrallel to one side of the house and then out into the yard. I need to know: 1)what type and size of pipe. I am thinking 3" feeders and 4" main, but don't know what type except for non-perforated; 2) How far from the house should it be? I have no idea here; 3) How deep should the pipe/trench be. I will find out what the frost line is. Should it be just below that? 4) Do I need to put in clean-outs?

Thanks for the help and if anyone can direct me to a good website or book with this info, that would be great too.

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Old 11-11-05, 08:49 AM
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Well first of all you're correct in choosing a non-perforated pipe. Solid PVC is the best coice. Then I've always had the idea that if you're going to do something you may as well go overkill. So I'd say that all you need is 4" pipe.
Then how far it should be is up to you, and where you want the water to emty out. I've always run the pipes out to the street curb, but that may require concrete cutting, then patching. So all you really have to do is look around your house, and see where the end of the pipe can be, so the outflow of water will not run back towards the house. And as far as how deep it should be? It doesn't have to be below the frost line, just a few inches below the surface should work. Then as far as clean-outs, all you really need is a T pvc joint in the soil conected to to main pipe nearest the house, then run an extender to the surface off of the T, then a threaded female, and male cap on top. But generally, unless you get a lot of leaves in your gutters and downspouts, cleanouts really aren't necessary, still a good idea though.
Anything else?
Old 11-11-05, 11:47 AM
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Thanks for the info. That's exactly what I was looking for.

Old 11-12-05, 10:23 AM
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Downspout drains

I had two oversize downspouts connected to 4" flex pvc.During downpours water would back up and shoot up out of downspout/pvc connector.The solution was to use 4" ABS (black rigid) pipe and problem stopped.I guess ridges in flex pipe slowed the water compared to a smooth pipe.I also put a 1/2" wire mesh over the open end of the pipe.Chipmunks would go up pipe and drive the dog crazy.It pulled the downspout off the house twice!
Old 11-10-08, 07:54 AM
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down spout drains should be extended at least 10-15 feet from the house. a drain emitter over the end of the pipe will keep out snakes, mice and soforth. the emitters can be bought at home depot, lowes and the like. Perhaps another hole or two in the bottom of the emitter would be nice.

11-10-08 kenneth house
Old 09-12-10, 07:55 PM
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I have a beginner's question. The down spount is rectangular. The underground pipe is round. What do I use to connect the two?
Old 09-12-10, 09:28 PM
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Alan...they make an adapter piece just for that purpose. It fits the rectangular gutter and whatever size pipe you use 3 or 4 inch.
Old 10-10-10, 04:47 AM
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Underground downspout drain - can it stay buried?

I'm researching pretty much the same do-it-yourself project: connecting 4 down spouts to 4" PVC pipes buried parallel to my home. The pipes will run the length of my house and about 15' - 20' past the house into the back yard under my garden. After taking into account the required grading and frost line, etc., the drains will be pretty deep so my question is: can the drain stay buried or am I potentially creating another problem by allowing the runoff to drain into the ground?

I've read posting on other blogs that suggest it's OK to leave the pipes buries with no above ground outlet but they gave no clear details as to what will happen to the water and how easily and quickly it will absorb into the ground. The potential problems I foresee are: drowned plants in my garden, a soggy yard leading to additional drainage problems.

All advise welcomed!
Old 10-10-10, 05:18 AM
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All of my downspout drain pipes open to daylight. My property is hilly and the water is deposited on the lawn 50+ feet from the house with no ill effects.

When it's raining hard there is almost solid water coming out of the pipe. I don't know of any system that can make that volume of water disappear under ground (French drain). Letting it drain onto the lawn or into a drainage ditch are probably the best options.
Old 10-12-10, 06:30 AM
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Originally Posted by Marley07631 View Post

I've read posting on other blogs that suggest it's OK to leave the pipes buries with no above ground outlet but they gave no clear details as to what will happen to the water and how easily and quickly it will absorb into the ground. Marley07631
definitely do not just let the pipe 'empty' into solid earth. I have 3 four inch pvc lines (1 for surface drains/1 for gutters/1 for footer) around my house and during a storm, they are pretty much full with water running down my yard (over 30ft from the house of course). I'm no engineer but i'm betting that much water emptying into solid earth , as you describe, would provide you with backed up lines and/or a sink hole. I dont have a solution for you but it's a guaranteed problem just to have a pipe run into earth.

if topography means you cant have this water drain above ground, perhaps the one time digging of a big hole and filling with large stones would work? just shooting a random thought out and i have no clue how to figure out how big the hole should be etc. I do know when i was a kid my dad put me on a project where i dug a hole 10 ft away from the house, about the size of a bale of hay but about 2x the depth and filled it in with rocks. then near the top of that hole on the 'outlet side' i trenched down the entire yard so i could lay down 4 inch pvc pipe that ran to the garden. i have no idea if this was a good idea or not but i was a kid so it was a fun project lol. my guess is the hole was meant to take the water, have it fill up then run further down into the garden in a controlled way and i do think this was totally underground. but i forget. i know the bottom of the hill always had 2ft grass was well watered from the laundry water lol.

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