# HVAC question concerning Pex



## pitterpat (Sep 25, 2005)

I bought a house 1 1/2 yrs ago that was built in 1956 so you know it has galvanized pipe for the water supply. I want to replace all of the plumbing pipes and am planning on using Pex and a manifold. Currently, the basement where the water supply enters the basement has an open ceiling and the water pipes hang under the joists.

As I stated I want to put the pipes up through and between the joists; the main pipe from the well tank goes under the joists because when the house was built the fashioned a cold air return using 2 joists and putting sheet metal on the bottom to box it in. Don't know if that was the process back then but that is what they did here. I would like to run the pex through this "made up" cold air return to keep the pex up and not dropped below the joists like it is now...was thinking about it all day and what I came up with was to drill a hole on both sides of the joist, put a length of PVC that will span both sides of this cold air return, then run the pex through the PVC. To seal around the PVC I would caulk it or put the aluminum tape around it to the joist.

I know this isn't a standard practice today but I don't think I can hurt the cold air return....when they put the sheet metal on the bottom all they did was nail it up there w/o putting any kind of tape on the seam; so what I do can't make it anymore leaky (air).

Does anybody see any problem with this?
Thanks, Pat


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## tenon0774 (Feb 7, 2013)

Let me count the ways...

If you planning on getting this project inspected, it will not pass.

If you're doing this for your own home, eh...

*Best* option, without pictures...

Relocate the manifold so that you don't have to "violate" a cold air return.

*2nd* Best Option (more expensive)

Have an HVAC mechanic come in to see if that "caliber" of chase is even necessary for (I'm assuming), the "newer" furnace you have. Talk to him/her about options for re-sizing, or re-mapping, the cold air returns.

*3rd* Option (...and we never had this conversation :whistling)

If you're gonna drill through the cold air return, don't "sleeve" the PEX with PVC. Drill a slightly larger hole (1/8 bigger than the O.D.) of the PEX, and seal it with LATEX spray foam insulation, or Fire stop insulation.

P.S.: If when you go to sell the place, the home inspector, (about the 3rd option) will point that out to you or the potential buyer and you may be left with "fixing" it at that point.

"Pay for it now, or pay later..."

"Do it right, ONCE."

just my two cents.


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## pitterpat (Sep 25, 2005)

tenon0774 said:


> Let me count the ways...
> 
> If you planning on getting this project inspected, it will not pass.
> 
> ...


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## tenon0774 (Feb 7, 2013)

Talk to your HVAC guy.

Relocating the manifold may be your "best" option, but he may have another idea.

Let me know how it plays out.

:thumbsup:


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## flashheatingand (May 3, 2008)

I have seen many systems in which the plumbing, and or waste lines were run through a return space without an issue. Yes, it's less than ideal. But, so is my 3" vertical leap when attempting to drive to the hoop. 

Make sure there are no joints within the return, and you should be alright.


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## Inner10 (Mar 12, 2009)

It's perfectly acceptable to run pipes and wires through cold air returns here.


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## Dr Heat (Dec 25, 2008)

It is a violation of the IBC to run pvc or pex through a duct. Copper, iron or galvanized can be acceptable under specific rules.

New construction as of 2013 disallows exposed wood in ducts.


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## pitterpat (Sep 25, 2005)

tenon0774 said:


> Talk to your HVAC guy.
> 
> Relocating the manifold may be your "best" option, but he may have another idea.
> 
> ...


The manifold won't be the problem, the main water line from the holding tank is the problem. The main line runs under the return from the holding tank (well) to feed all the other lines.


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## pitterpat (Sep 25, 2005)

Dr Heat said:


> It is a violation of the IBC to run pvc or pex through a duct. Copper, iron or galvanized can be acceptable under specific rules.
> 
> New construction as of 2013 disallows exposed wood in ducts.


It technically is not a duct....it's the joists that they sheet metal on the bottom to make the cold air return. LOL.

Old construction circa 1956.


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## HVAC1000 (Feb 4, 2013)

pitterpat said:


> It technically is not a duct....it's the joists that they sheet metal on the bottom to make the cold air return. LOL.
> 
> Old construction circa 1956.


Ya that's how we used to do it around here til the early 2000s when it became code to fully sheet metal it in, but that is 100% a duct, at least as far as your municipality and inspector are concerned


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