Corrugated Drain Pipe Reducer (4" to 3")

I built this to change from 4" corrugated drain pipe to 3" pipe. Normally you want to go the other way around, but in my case, I had reasons to want to run 3" pipe, and since the pipe is fed by a 3"x2" downspout, I figure there's no reason to stick with 4" pipe. It's designed so that the OD of the 4" pipe fits within the adapter, and the ID of the 3" pipe fits over the other side, so that water doesn't flow around the adapter. Of course, if the 3" pipe can't take what the 4" pipe is putting out, that might be a problem - but that doesn't seem likely since my downspout capacity is less than a 3" pipe.

I designed the straight adapter first, and printed it. Because it has a lip that the water must go up in order to enter the 3" pipe, this version is mainly suitable for steep slopes (such as I had). I printed it without supports, and had a minor bit of string that I just ignored, so after printing, I modified the design a little to reduce the overhang angle. I think it will print better (still without supports), but have not tried it. The one in the photo is the unmodified version that I printed.

After working on the straight adapter, I modified it for an offset, which will work much better when you don't have much slope. But I never printed that version (don't need another adapter right now) - so you're on your own. My recommendation, even though I've not printed this version, is that this version is a better design for most cases.

They sell adapters in hardware stores, but they are overpriced, and really poorly designed IMHO.

I used PLA+ because it's more durable than regular PLA. PETG would be better, but I don't have any. I buried the pipe and adapter after taking the photo, but I heard it takes decades for PLA+ to break down, so I think I'm good.

Print Settings

Rafts:

No

Supports:

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Infill:

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Category: Outdoor & Garden