# Retaining wall drainage



## werc

I have loved reading all the posts on this site, and am really impressed with everyone's knowledge! So, I have what may be an easy question for some. I am building a 3 foot retaining wall running 150 feet out of Diamond blocks from HD. I understand that I need to put drainage pipe behind the wall to help keep the wall structure. However, I just cannot figure out how to finish the end of the drainage pipe. So, I will run it to the end of the wall, but do I just run it out past the end and leave it open ended? Seems to me that is a sure way for it to get clogged, but if I bury it, it won't drain. Any help is appreciated, as I just cannot figure this part out.


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## SecretSquirrel

The short answer is; Yes, the water has to have somewhere to go.

Your options are to leave the end of the drainage tile "open ended" where it will flood out to that point or you can connect it to another underground drain pipe to have it drain elsewhere. Unless you have a torrent of rain, most of the water will be absorbed into the ground and the drainage will be a non-issue. The slotted drain tile (slots down) should be level, behind the wall, but subsequent drainage pipe should be pitched a good 1/4" per foot. Be sure to surround your drain tile with gravel and to encase that with landscaping material to avoid the pipe from getting clogged. You could put a screen on the end point to keep critters out.

A third option is to put tees into the drain tile every 10' to 15' and have each tee exit the wall and the area downslope of the wall will be the drain field.


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## RippySkippy

In addition to what SecretSquirrel said, depending on your soil type, you might want to use the drainage tile that has the sock on it...it will help keep the soil out of the tile and from plugging.

To finish the end, transition the drainage pipe into a piece of schedule 40 PVC, and have the end exposed as needed. It's less likely to collapse that the drainage tile. As mentioned don't forget the rodent barrier on the end of the pipe.


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## werc

Thank you for the tips, that helps put it in some perspective for me!


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## amdspitfire

Bumping this thread, I have a simmilar project going on and have a question.

1. How should I vent the drain tile to daylight, I have read that the retaining wall drainage needs an exit every 50ft.

http://www.allanblock.com/Retaining...l/soilswater/image/DrainTile4229_Copy5415.jpg

Should the perpendicular exits run under the wall?? Should blocks be cut to allow the the drain to come through it?

http://www.allanblock.com/retainingwalls/Installation/Landscape/watermgmt/image/DrainTileFace337.jpg

2. Drain pipe behind the first row of blocks or behind and under with base rock (the two pics show each)?


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## concretemasonry

Both the Anchor and Allan wall systems are similar to all the other SRW wall systems.

You need a permeable, clean granular backfill (not "dirt") that allows the water to flow through it. That eliminates the need for an outlet. If you have an excess of groundwater or the need for an outlet, connect the perforated pipe to a solid pvc pipe to carry the excess groundwater away to an appropriate location.


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## werc

Well, here is what I did for what it is worth (at least the wall is still standing!) I did put a drain pipe behind the wall, but I only daylighted it at the ends. Even at that, I did not really daylight it. I just dug a deep hole at the end, and filled it with rocks. I think this is called a dry well. I am not sure it really works, but like I said, the wall is still standing. I do notice that water definitlely comes through the face of the wall. Not a flow, but the face remains wet a day after a heavy rain. This leads me to believe that water is also escaping from the wall face. Here are some pictures of my project if it helps any.

http://www.pbase.com/werc/retwall


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## RippySkippy

WERC -- what a great improvement...from a quick scan, it looks like you did it right...congrats!


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## amdspitfire

werc said:


> Well, here is what I did for what it is worth (at least the wall is still standing!) I did put a drain pipe behind the wall, but I only daylighted it at the ends. Even at that, I did not really daylight it. I just dug a deep hole at the end, and filled it with rocks. I think this is called a dry well. I am not sure it really works, but like I said, the wall is still standing. I do notice that water definitlely comes through the face of the wall. Not a flow, but the face remains wet a day after a heavy rain. This leads me to believe that water is also escaping from the wall face. Here are some pictures of my project if it helps any.
> 
> http://www.pbase.com/werc/retwall


Great project and pics, I got the base ready and waiting for the blocks to be delivered, so far it's been about 2 weeks and doing everything by hand! My wall will be 130ft long, 3ft height but in my backyard! You are very lucky the could deliver the blocks right besides your project.


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## Drake Equation

Nice pictures. I'm curious...did the white plastic drainage tile/pipe exit somewhere?


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## KUIPORNG

*What a cute digging machine...*



werc said:


> Well, here is what I did for what it is worth (at least the wall is still standing!) I did put a drain pipe behind the wall, but I only daylighted it at the ends. Even at that, I did not really daylight it. I just dug a deep hole at the end, and filled it with rocks. I think this is called a dry well. I am not sure it really works, but like I said, the wall is still standing. I do notice that water definitlely comes through the face of the wall. Not a flow, but the face remains wet a day after a heavy rain. This leads me to believe that water is also escaping from the wall face. Here are some pictures of my project if it helps any.
> 
> http://www.pbase.com/werc/retwall


 
my 4 years old son is going to love this "toy"... how do you get it, I think you probably rent it.... how much per day.... gee.... I want to get those... even for 4 hours ... for my son to play with it.... not exactly for this reason only.... I do have a lot of soil need to move around for my patio project.... got to go to googling now....


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## werc

Drake Equation said:


> Nice pictures. I'm curious...did the white plastic drainage tile/pipe exit somewhere?


 
No, at both ends of the wall, I dug a deep hole and filled the hole with rocks. The drainage tube drains into those "dry wells".


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## werc

KUIPORNG said:


> my 4 years old son is going to love this "toy"... how do you get it, I think you probably rent it.... how much per day.... gee.... I want to get those... even for 4 hours ... for my son to play with it.... not exactly for this reason only.... I do have a lot of soil need to move around for my patio project.... got to go to googling now....


 
That was the absolute best thing I have ever rented! Do a search on a Toro Dingo. That is what I originally reserved, but the rental place was out of them. If I remember correctly, it was about $175 for a 24 hour rental. That included tax, the rental insurance, etc.


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