How to run agi pipe behind retaining wall?

newbiegardener

Hi there, 

I've been on this project I've had for a while and finally have time to get it done so looking for advice for the first step, running an agi pipe behind my retaining wall to drainage in front of my house (can see in the picture). 

I'm planning to do it along the blue line on the photo I've attached and have these items I'm planning to buy with a rough indication on how to do it below. Does anyone have any tips, suggestions or remarks about what I plan on doing as this is far out of my normal line of work! 

agi pipe

blue metal

draincoil tee

draincoil end caps

• I plan to dig a trench 5000mm along the retaining wall and a 2000mm trench from the first trench to the water pipe with a 70mm fall from the high point to the water pipe. 
• The trench will be 350mm deep for the 100mm draincoil surrounded by blue metal. 
• As there is a 90 degree turn in my plan, I was going to use the draincoil tee and end caps as I wasn't sure if the draincoil could make the turn without it. 
• I'll then connect the agi pipe to the pvc pipe. I'll then backfill over the blue metal and agi pipe and use any additional soil for my next project. 

Please let me know if there's anything I've missed!

Thanks in advance, 

Dean

JacobZ

Hi Dean (@newbiegardener),

Your plans sound good and there is not too much else I can add.

I don't think you need to add a tee and an end cap. Agi pipe is quite flexible and an abrupt 90° turn is not ideal if it can be avoided. I'd just lay the agi pipe out before you dig the trench so you can see where you need to dig to allow it to comfortably make the bend.

I would also suggest lining the trench with geotextile membrane as this will prevent smaller sediment from washing into the blue metal, which can overtime block the drainage channel. It is a simple addition that will keep your drainage trench working as intended for longer.

Outside of these few things, you are certainly on the right track. By the looks of it, your front yard will love the extra work you are planning to put in.

Let me know if there is anything else I can assist with.

Jacob