drain pipe, holes up or down?

[B]

What kind of corrugated plastic pipe would you put behind a retaining wall? Slitted or with holes, if with holes, would the holes go up or down? And what about fabric sleeves vs. burying the pipe under gravel wrapped with landscape fabric? I've heard every combination of answers. What's your answer, and why? Can you give a link to reliable info? Thx.

 

[Rudy]

What kind of corrugated plastic pipe would you put behind a retaining wall?

I'd use the white PVC (3" or 4") with the holes drilled in it. I dont like the black corrugated stuff (Big "O" pipe). I ve seen it collapsed. Around here, they sell a filter paper of sorts thats placed over the gravel above the pipe to keep the dirt/fines from working its way down to the pipe. Thats what all the builders go with around here.

 

[Vic Dura]

What kind of corrugated plastic pipe would you put behind a retaining wall? Slitted or with holes, if with holes, would the holes go up or down? And what about fabric sleeves vs. burying the pipe under gravel wrapped with landscape fabric? I've heard every combination of answers. What's your answer, and why? Can you give a link to reliable info? Thx.

White PVC with holes facing down so water doesn't have to get 3" deep to enter pipe. Fabric sleave *with* gravel to provide extra protecton for holes from becoming clogged.

 

[Robert Allison]

White PVC with holes facing down so water doesn't have to get 3" deep to enter pipe. Fabric sleave *with* gravel to provide extra protecton for holes from becoming clogged.

Exactly right. I do add another layer of fabric around the gravel (and you need to use drain rock or river rock). So to summarize;

Lay a sheet of filter fabric in the bottom of the trench. Fill with 1-2" of 1-1/2" drain rock. Lay your pipe (holes down) in the center of the trench with a sleeve of fabric material around the pipe. Fill the trench with about 1-2' of 1-1/2" or larger rock. Cover with another sheet of filter fabric and overlap the edges of the bottom sheet with the top sheet. Cover with dirt.

Here is a pdf detail of a french drain:

http://ci.marysville.wa.us/publicworks/standards/drainage/4080006.pdf

 

[CR]

What kind of corrugated plastic pipe would you put behind a retaining wall? Slitted or with holes, if with holes, would the holes go up or down? And what about fabric sleeves vs. burying the pipe under gravel wrapped with landscape fabric? I've heard every combination of answers. What's your answer, and why? Can you give a link to reliable info? Thx.

As said by others, PVC holes down. My reason for PVC over the corrugated pipe is that sometime in the future you may have to run something up the line to clean it out. If you have to remove roots the cutter tool will come out with chunks of black corrugated pipe as well as the roots.

CR