Corrugated Drain Pipe Outlet from 4" Block Wall (after-assembly pass-through)

We built a decorative concrete block wall (Home Depot 4"x9"x8" deep blocks) a decade ago, but had to reroute a gutter downspout drain line recently. This required burying a new line of corrugated drain pipe, but we wanted to terminate the line above ground so that we didn't have to dig completely under the wall and then dig trenches for dozens of feet beyond. The best way to do this was to chisel away part of one of the lower blocks in the wall, and then excavate out behind the wall to pass a "culvert" through the opening - and still have it look nice.

This is a 3-component build. Part 1 is the adapter between a 3" corrugated drain pipe (if you have 4" pipe, look for my 4" to 3" adapter posted separately). The adapter is buried behind the wall (I printed this in brown PLA+ because it should be more durable than PLA, and I didn't have any ABS or PTEG available). I didn't care about color, because it's buried. The 2nd part is a square tube that passed between the blocks - sized to a little under 4" tall, so I could hammer-drill/chisel out a portion of a block without having to dismantle the wall and make it look like a retrofit. I printed this with gray PLA+ to sort-of match the block wall color. Part 1 simply inserts into Part 2, but to ensure they stay together, I glopped some Gorilla glue onto the end of Part 1 so that part 1 and part 2 stay connected. While that might not be necessary, it seemed like a good idea, because if you pull Part 2 out of Part 1 after it's inside the wall, it might not be easy to get them aligned and back together. Part 3 is simply the grate/grill that screws into Part 2 with (in my case) stainless steel #8, 3/4" screws. I printed this in Black PLA+, but gray PLA+ would have been fine too.

Overall, it makes an elegant exit to "daylight" downspout water beyond, or through, an existing retaining wall with 4" tall blocks, and makes it so you don't have to rebuild the wall (which I was unwilling to do, at my "advanced age"). Since one part inserts from outside the wall, and the other parts inserts from behind the wall (after excavating behind the wall), it was fairly easy to put these together.

One might ask why I didn't just buy one of these... Well, I couldn't find anything at Home Depot or Lowes that looked or worked like this, and even when I found something close, it cost several times what it takes to print this with PLA+. You decide. I'm a retired engineer, and I do this for fun.

The one in the photo is a bit undersized at the female end that accepts the 3" corrugated pipe. I didn't want to waste the filament to reprint it, but the version posted here was corrected and will hopefully work better. If you print this, please post a "Make" and let me know if the size for the 3" pipe came out better. It should encounter some resistance as it passes over 4 bumps added to retain the pipe, but it should still push in and stay put.

I used PLA+ because I didn't have any PTEG or ABS on hand, but PLA+ is supposed to degrade over several decades (or a century or more), and I won't live that long, so it should be fine. I did not use supports, and everything was printed in the orientation as shown. The version in the photo is what I printed, but the version in the attached model is the modified version with improvements - I did not print this version (didn't want to waste the filament), but it should print fine.

Category: Outdoor & Garden