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horizontal pvc pipe thru new concrete pedestal 2

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AskTooMuch

AskTooMuch

Petroleum
Jan 26, 2019
268
I have an existing horizontal pipe that will run thru a new concrete pedestal.
Pedestals is 2'x2'x 4'. Horizontal pipe is 4" dia and is located just a few inches above footing and about 3" from edge of pedestal.
I can make the pedestal bigger like 3'x'3' and add additional rebars.
But I want to make sure the pvc pipe can take the stress, what is the best way to detail this to limit the stress on the pipe.
 
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I don't see the PVC taking meaningful stress. The concrete will be the much stiffer thing in the mix. Obviously, the pedestal needs to work considering the PVC as a void.

 
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It may be worth considering the impact of foundation settlement on the PVC though. Sometimes we isolate these things a bit

 
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Pipes is existing. A sleeve will have to be split in 2 and either welded or clamped together.

Kootk, you don't see pipe getting crushed?
 
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What do you see doing the crushing? The wet concrete weight during casting?

 
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Once the concrete has set, I would expect all axial load to travel through the concrete, which should be by far the stiffest path, and not through the PVC.

 
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If no need to support the existing PVC pipe, the small gap between the top of pedestal (2x2x4) and bottom of the pipe is fine. If support needed, consider using the steel channel on the pedestal for the pipe. Imo, no need to increase the pedestal to 3x3.

 
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Mk3223, there is no gap betwen pedestal and pvc. Pvc will run thru it. Pvc is located just above footing and at the bottom of pedestal.
 
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It can be easily done by providing pipe Sleeve of bigger than 3". sleeve or half cut pipe will be placed at bottom and than at top and welded together afterwards
Document1_hjtrym.jpg
 
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Is the pipe a pressure pipe or a gravity pipe?

If you consider the pipe as a shutter, once the concrete has set, and in theory if you could remove the pvc then you would be left with a concrete pipe instead?
 
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Looking at this from the pipes perspective,

The external pressure from the wet concrete should be no problem at that sort of size.
Once set the concrete takes all the load.

Far worse though is the fact that you've created a rigid anchor / fixed point. PVC is notorious for being brittle and an settlement to the concrete or the pipe will break it or crack it.

either replace tis section with PE pipe or make the hole in the concrete bigger as shown above.


Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
 
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Wrap the pipe with pipe insulation, then wrap the insulation in visquene to keep the paste from penetrating the insulation. Place the concrete and forget it. No crushing stress on the pipe as others have noted...only potential shear stress from settlement, but the insulation will solve that.
 
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I was gonna say take some 5" or 6" PVC, split it and then wrap it in duct tape to re-assemble and I like Ron's idea as good.
 
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"Pipe insulation" is too vague. Foam will crush under weight of concrete. Solid insulation might be the same as concrete.

You really need air space and this is vey standard.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
 
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The advantage to using insulation around the pipe is that it keeps the pipe in the middle of the 'sleeve', allowing for relative movement in any direction. For a spread footing, you would expect any movement to be settlement of the footing (generally a good assumption, but not always), but if the footing is on a deep foundation (piles, etc.) then the movement could very well be the opposite. A pipe lying in the bottom of a sleeve is no better off for that condition than one with no sleeve at all.
 
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You should also check the axial and flexural/shear (if applicable) capacity of the pedestal based on its reduced cross section due to the void created by the pipe
 
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