Kitchen Sink/Dishwasher Supply Route on Concrete Block Wall

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Dave Osborne

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I have a kitchen sink and dishwasher under a fairly large window against an exterior concrete block wall. For venting there will be an air admittance valve beneath the sink in the cabinet, which is apparently allowed in my area for this type of scenario because the block wall does not lend itself to accommodating a vent pipe and the big window seals the deal, making a traditional vent pipe a non-option. Even offsetting the vent around the window was not a practical solution.

But anyways, the question now is planning the supply line route for the sink and the dishwasher. I have a home-run PEX manifold distributing water to all my fixtures all above the slab (there is no basement), so the pipes run through a utility chase just below the ceiling. So the PEX pipes come down from the ceiling and run down the inside face of the blocks inside of insulation sleeves along the side of the window. They are between furring and rigid insulation, so the pipe is between the drywall and blocks, shielded in key areas where an errant cabinet screw could possibly hit them.

So, at this point the PEX pipes have descended to base cabinet level, but they are about 4 feet laterally away from the sink base cabinet. Should I drop them all the way down to the floor; notch out the bottom of the cabinet boxes and have the supply lines run laterally along the floor and pop out in the sink base from the "floor" of the cabinet? Or keep the pipes in the wall cavity, cutting across furring until they reach the back of the sink base and pop out from the back wall of the cabinet?

Keeping it in the wall seems to be the natural solution, just not sure if there are any considerations that I may be overlooking though. Also not sure how best to bend/stub out the pipes from the wall; there is not much room in the furring/insulation cavity (1.5") for a bend. The pipe would exit the drywall and penetrate the cabinet before completing the bend, they would be coming into the cabinet at an angle. I guess that I could crimp on 90 elbows so that they can turn on a dime, but how I can brace them? I don't think that there's enough space for those plastic stub out clamps and I don't think that they should just be loosely sticking out of the wall.

Any thoughts, insight or ideas are welcome and appreciated, thank you!
 

wwhitney

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Dave Osborne

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No opinion on what height to run the water line laterally, toe kick height or final stub out height.

For stub outs, how about preformed copper stubs with a 90 at the end? E.g. for expansion PEX, something like this:
https://www.supplyhouse.com/Wirsbo-...b-Ell-1-2-PEX-LF-Brass-x-1-2-Copper-3-1-2-x-8
That has enough pipe length before the bend that you could use a copper strap against the wall.

Cheers, Wayne
Thanks so much, I do have some left-over copper stub outs. Didn't realize that strapping them to wall was an option, that seems like the way to go. I want to keep at least 3/4" insulation between the pipe and block wall, but the bend radius seems tight enough that it should be fully straight by the time it exits the drywall (even if it wasn't I could just make the drywall holes slightly oblong and have a little bit of the curve sticking through).
 

wwhitney

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I want to keep at least 3/4" insulation between the pipe and block wall
Good idea, I think I'd avoid having the copper in contact with the concrete block. If you're using rigid insulation, it may not have the compressive strength to support the strap, you might need to cut out a rectangle of insulation and replace it with a rigid material attached to the concrete block and then strap the pipe to that. E.g. wood or PVC trim.

Cheers, Wayne
 
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