# Pex, exterior wall



## add50317 (Feb 22, 2010)

Should I be hesitant putting pex waterline in an exterior wall? It will only be 4 foot max long.

This is in Des Moines, IOWA.

THX


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## Daniel Holzman (Mar 10, 2009)

I would not put any type of water line in an exterior wall, it gets pretty cold in Iowa in the winter, unless global warming has changed the temperature from when I lived next door in Wisconsin. Although PEX survives freeze better than copper or rigid plastic, it is not designed to be frozen.


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## SeniorSitizen (Sep 10, 2012)

Any supply pipe can be within an exterior wall as long as it it placed on the warm side of the insulation. If it ever gets cold enough to freeze it there any occupants would have been long gone and the structure should have already been winterized.

The problem usually lies with a builder lack of knowledge.

I should have included and/or the builder doesn't give a damm.


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## TheEplumber (Jul 20, 2010)

The way I handle cold walls is to put a thick layer of rigid insulation against the ext. sheeting. Cut it tight to the studs and foam​ any gaps.
Then use standard Batts for the rest of the stud bay.
Put your pipes to the inside face, right behind the drywall.
Is this the best way? Nope, the best is to find another route

Sent from my XT1650 using Tapatalk


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## Bondo (Dec 8, 2007)

> Is this the best way? Nope, the best is to find another route


Ayuh,.... I moved my old copper run against the wall pipes when I went to pex, up from under the floor,....

I will say, pex survives freezin' quite well, except for the fittin's, which still get busted when frozen fulla water,...
That's why I like the bendability of pex,.... Less fittin's,.....


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## Yodaman (Mar 9, 2015)

What size is the wall cavity?


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## add50317 (Feb 22, 2010)

The wall is a normal wall cavity..2x4's. That is what I thought...not a good idea..but I wanted to get other input. We'll see, I might just go up through the floor!


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## SeniorSitizen (Sep 10, 2012)

The main reason pipes freeze in outer walls is DIY'ers not being informed or not believing information and in the case of contractor construction: 

_the plumber got his work completed first and no way in hell is the insulation contractor going to slow down his job by tucking his insulation in behind that dam plumbing the stupid plumber put there._


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## Yodaman (Mar 9, 2015)

add50317 said:


> The wall is a normal wall cavity..2x4's. That is what I thought...not a good idea..but I wanted to get other input. We'll see, I might just go up through the floor!



Are you going into a vanity cabinet or up to the next floor?


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## BIG Johnson (Apr 9, 2017)

Is it exterior to the outside or to a garage? Is on the wall that receive ps prevailing winds?

If it backs to a garage you could probably get away with it in a 2x4 wall if you insulate the wall properly. Other than that I wouldn't chance it. 

sounds like it's a washing machine box? If so, just mount the box to the drywall, the machine will block it anyways.


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## jlhaslip (Dec 31, 2009)

Big NO! NO! running plumbing in any insulated wall up here.


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## Yodaman (Mar 9, 2015)

BIG Johnson said:


> sounds like it's a washing machine box? If so, just mount the box to the drywall, the machine will block it anyways.



I agree, somewhat. I wouldn't bother with a box at all. Fasten a pc of 1/2" plywood between two wall studs about 40" high, paint it the same color as the wall. Surface mount your pex lines and valves on the plywood and hide it all behind the washer. 


Unless someone makes a flush mount box with the supply ports on the surface. I have never seen one, kind of self defeating.

You should be able to find a flush mount box for the drain only.


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