How Does Perforated Drainage Pipe Work?

How Does Perforated Drainage Pipe Work?

Our subscribers are crazy intelligent. I just love it. You guys ask the best questions and they're legit. So here's one that I get asked a lot, so I'm going to explain it. People are always saying, they're always saying, how does the water move in the pipe when there are all these holes because of the thought behind it is those the water just fall out as easy as it goes in? So I get that. That's legit guys trying to figure out how this pipe works.

Don't screw yourself into the ground, man. It's this simple. We wanted these big outlets for two reasons. One, the water goes right into this pipe and this pipe acts as a giant void. Just like we go up in size on aggregate. The larger the aggregate, the bigger the voids. Say you don't have big aggregate available to you. Say you get stuck using small stone. Well, then it's even more important that you put two pipes in because you create the voids. This is a giant void, two, four-inch pipes. That is a monster void in your system. And I'm gonna teach you some more stuff here in this video real quick because the guys want to start putting the stone in.

Now over here, we're going to have a Tee and the discharge is going to go to the storm drain. With these big inlets in the High Octane, the water collected in this pipe just passes through into this pipe. Now we're going to put a Tee here, but that's how we do it. People always say, Hey, what's going on here? You're not connecting these two pipes. Well, it's a big void. It's like having monster aggregate and you'd have to have 12 inch or 18 inch, you round rock to great the kind of voids we're creating. So that is what we do here.

Now see how big these voids are? Any dirt or contaminants will pass right through these voids. They'll pass right through these pipes. Can you believe that? It's awesome. That's why we had Baughman Tile open up the inlets on the High Octane. [...]

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French Drain Man – Michigan’s Yard Water Drainage Experts. Masters in the art of constructing contained French drain systems & curtain drain systems that and fix your yard drainage problems for years to come. Over 30 years’ experience in solving yard water drainage problems in Oakland, Macomb, Lapeer, and St. Clair Counties.

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[garystevens]

So you never explained why / how the water never exited the bottom of the pipe. Like you said its full of holes. Is the cloth waterproof. Do you always need that? Can you lay the pipe directly on to the soil?

[DavidShercliff]

The reason water flows through the big void is because of what is known as. Relative permeability. The bigger the void the faster the flow. A pipe is one big long straight void where water can accelerate. If water goes through gravel it has to wiggle about to go through and therefore goes slower . If it goes through soil it goes quite slow and if clay doesn’t go at all.

[andrewgill]

Thanks for explaining this. doing my first French drain and couldn't get my head around all the holes and how it transfered water. lost sleep for no reason haha.

[DavidShercliff]

I note FDM hardly mentions the fabric but does describe the effect. The reason the pipe runs dirty at first and then runs clean is the fabric. It allows water to flow quickly through it but doesn’t allow big particles through from the soil. It is in fact a filter. True some of the initial dirt is from the bad drainage stone but the main is the first bit of soil which goes through the fabric and then stops because of a structure that builds up in the soil called a filter cake. If the fabric wasn’t there the soil would keep piping through into the drain and the ground would settle.

[mae]

FDM, you should do a video on why you put the pipe on the bottom of the trench. I now realize that most tutorials on the internet say to add gravel first is because the pipe they talk about only has holes on the bottom (like solid PVC). So if you put that on the bottom of your trench, it will clog and the water will never get into the pipe. The pipe you use is perforated all around, so if the bottom clogs, the water still has the rest of the pipe circumference to flow into the center. I did a little bit of both when I did mine (since I didn't have this epiphany until after). I put a super thin layer (like 1 rock thick, like you spread them out on a cookie sheet), then put the pipe in, then filled the rest with stone. I'd like to send you pictures. Dug out the old home owner's TWO failed french drain systems. Socked pipe!

[antonios]

Thanks for the video. Is this pipe twinwall or single?

[ForViewingOnly]

It still seems to me like a pipes with perforated sides and top, and a solid bottom, would drain the water away more effectively. I need somebody to explain in scientific terms why this wouldn't be the case.

[Luke-A]

I know nothing about this but I'd guess that water doesn't leave the pipes because it's following the path of least resistance, gravity is pushing the water down once it gets to ground level its easier to travel along the pipe than it is to keep moving through the ground beneath the pipe.

[TLCify]

Thank you for you explanations on french drain topics. In this video I don't understand why you run the downspout water to a pop-up, when it looks like you could run the solid yellow pipe another 50-100 feet to the storm drain. Why not run the downspout water to the same storm drain as the High Octane pipe?

[Makebuildmodify]

I'm installing a drain with a deep trench, 3' or 4' deep. Would it be better to use two 4" (25.12 sq. in. cross section) pipes or one 6" (28.26 sq. in. cross section)?

[PlusUltra]

Please help me figure this out: the "real" chanel that drives away the watar is the "tunnel" made out of water proop membrane? We just add and then cover the perforated pipe so that we have more void (volume, space) through which the water will go down?
Because if it was all just gravel & membrane, then the "tunnel" could transport less water through it?

[protectork]

my contractor put this for down-sprout near the foundation. it is under concrete and has gravel . is this good idea.

[sethbrownell]

Dear Mr French Drain Man, I have a dry well on the side of my driveway 2 feet by 5 feet deep it has a grated top I have sandy soil so it drains good in the summer. My issue is winter I live in Vermont and it freezes then when we get the odd rain storm in February my driveway floods and water gets in my house. There is no storm drain to connect it to nor is there a place to let the water drain down hill. I’m wondering if building a French drain that is connected to my dry well would help the water drain out of the dry well?

[papitsunami]

Do you need one if the retaining wall is not very high, say only 20cm high?

[cge]

Basically you are making sure the puddle is only under ground which keeps the surface dry. When the puddle becomes deep it runs out the end.

[andg_rodg__real]

why do you have paper underneath the pipes?

[joshuatonecha]

That's a waterproofing contractor for you. 6 minutes to say nothing. I would have loved to hear the "why this costs 15k" speech. "Well check out all the holes and colors!"

[kerematamer]

Hi I leave in aus I leave in slope so each time it rains water goes underneath the house know iduged to footings the pipes comes with the socks on it so iam sure should uput geotextile o it before I put the gravel on it

[trvorb]

Seems the trench carries the water. Will a wrapped trench with large rocks do the same?

[asadandrew]

My downspout is connected to a perforated corrugated pipe, should I change it to a solid?