Flex in 4" ABS

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Zimm0who0net

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I'm putting in a utility trench with ABS and I need to bend around an obstacle. I need to bend out about 2' in a 20' span and then back again. I think that's a 26' radius (if my geometry skills still hold up). It's 4" ABS. Is this possible, or do I need to cut the pipe and put in fittings? Theoretically I could step down to 3" ABS if that makes it easier, but I'd prefer the bigger stuff for possible future expansion.
 

Jadnashua

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None of the stuff is designed to be bent! IT induces stresses that may be problematic down the road. It does soften if it gets heated. There's also a limit on how much change of direction you can put into a drain pipe before you are required to install a cleanout, and it can make it harder to run a snake through, if that's ever required. Bends will slow down the flow, so you may want to ensure you have the slope for a smaller pipe (1/4"/foot, while a 4" pipe can often get by with 1/8"/foot, if it is straight). When trying to avoid level or bellies in the pipes, the smaller the slope, the harder it is to accomplish, especially with a flexible (rigid!?) pipe.
 

hj

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I get the impression that this is NOT a drainage pipe, but rather a conduit of some kind. if so ABS will "bend" that much the problem you will have is bending back afterwards, since it will have to make THREE bends to get back in line.
 

Zimm0who0net

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I guess I should just link an image of the whole trench plan and see what you guys thing. The "wavey" part is to keep the trench at least 2' away from footings or the pool. (The circles are just guidelines so I keep at least 2' from these features) I thought I might be able to just bend around that angle (like I'll probably be able to do with my 3/4" PVC for the water service), but using fittings will probably better.

Here's a link. You can click on it for a zoomed/closer view: http://i.imgur.com/hFXvsKy.png
 
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Dj2

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If you go to the plumbing supply place and check out the ABS pipes, you will probably be able to find a few with curves to get you through the top curve in the plan. These curves are caused by poor support during shipping, sometimes making them useless for a drain line that has to maintain an acceptable drop. You could even get them at a discount, if you ask.

Also, you could dig the trench in such a way to allow them to fit in.

The two curves at the bottom of the plan would need fittings.
 

Jadnashua

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Bending a plastic pipe while maintaining the typical slope can be tough leading to problems with blockages down the road. It's easier to grade the ditch if the pipe is straight, even if it does have a fitting or two in there to change direction.
 
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