Insulating water lines in attic?

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Mikey

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With the possibility of freezing, wouldn't pex be better than cpvc?

Good question. I'd love to know that as well. I chose CPVC at the time because PEX was somewhat controversial, and tooling was expensive. I think times have changed, but haven't looked into it in depth.
 

ilya

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"Insulating properties of cpvc"!? Listen to the experienced tradesmen guys.
 

Mikey

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"Insulating properties of cpvc"!? Listen to the experienced tradesmen guys.

I'm an engineer, not a gossip; here are the numbers:

Thermal conduction is defined as “transfer of heat from one part of a body to another part of the same body, or from one body to another in physical contact with it, without appreciable displacement of the particles of the body.” This definition leads us to the commonly used “K” factor which refers to thermal conductivity.

Typical “K” Factors
Material BTU/h/SF/F°/in.
Copper 218.0
Cast Iron 26.8 to 30.0
Steel 26.0
Concrete 0.54
Brick 0.4
Wood 0.06 to 0.12
PVC 0.11
CPVC 0.08

And, in the gossip department, here's what a (presumably) skilled tradesman had to say about CPVC in another forum:

Will a CPVC system offer a financial advantage to Owners in terms of utilities expense?

Yes. The thermal conductivity of a copper system is 2500 times that of a CPVC system. The improved insulating characteristics associated with CPVC can generate substantial long-term savings for an energy conscious home-owner or tenant. CPVC will keep hot water hot for a much longer period of time than copper tubing.
 
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Mikey

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I didn't mean to be snotty in my previous post, and am listening to the experienced tradesmen. I'm going to relocate the attic plumbing as recommended, but will stick with CPVC. I will also take this opportunity to install a return line for a hot water recirculation system in the same insulated chase; I will probably use PEX for that, to simplify the installation, but I'm still doing research on that. Looks like PEX's thermal conductivity is on the same order of magnitude as (but higher than) CPVC, but I've seen conflicting numbers which are yet to be resolved.

SRQGator, you might consider this as well:

https://terrylove.com/forums/showthread.php?1233-Hot-Water-Recirculation-Choices&p=282840
 
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HomeRepairGuy

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I'm going to relocate the attic plumbing as recommended, but will stick with CPVC. I will also take this opportunity to install a return line for a hot water recirculation system in the same insulated chase; I will probably use PEX for that, to simplify the installation, but I'm still doing research on that. Looks like PEX's thermal conductivity is on the same order of magnitude as (but higher than) CPVC, but I've seen conflicting numbers which are yet to be resolved.
Once you pull pex tubing through an attic, you won't want to go back to anything that requires solder or cement at turns. Just plan your pex run so turns are all curves and that you don't have to use elbow joints in the attic. No joints in attic equals no worries about leaks. For tight turns, use pex supports made for the size of tubing you use, but strive for gradual turns without those supports to allow the pex to expand and contract in the rest of the run. Put joints only at the start and end of runs. Pulling that flexible pex tubing through an attic is pure joy. Be sure your attic is rodent proof.

HRG
 

Mikey

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Rodent proof, huh? How about snakes? I've never seen evidence of rodents, but I've seen several shedded skins. No idea how old they were. Maybe that's why there aren't any rodents.

Bend radius should be no problem -- 5" for 1/2" size, 7" for 3/4" (8 times the OD), but I'd probably keep most of the CPVC drops, since replacing them will require opening walls. And, of course, there will be joints throughout the trunks, so the joint-proof nirvana ain't gonna happen. Are Sharkbite style fittings OK for in the attic? Folks seem to be divided on those.
 

HomeRepairGuy

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Rodent proof, huh? How about snakes? I've never seen evidence of rodents, but I've seen several shedded skins. No idea how old they were. Maybe that's why there aren't any rodents.

Bend radius should be no problem -- 5" for 1/2" size, 7" for 3/4" (8 times the OD), but I'd probably keep most of the CPVC drops, since replacing them will require opening walls. And, of course, there will be joints throughout the trunks, so the joint-proof nirvana ain't gonna happen. Are Sharkbite style fittings OK for in the attic? Folks seem to be divided on those.
Attic must be proofed against anything that can gnaw on pex lines. Rumor has it that the water in the tubing can invite gnawing, especially if rat poison was used since it dehydrates the rats.

Personally I won't have any joints in my attic be they soldered or cemented and especially no sharkbite type fittings. That's why I went with pex with joints only at beginning and endings of runs.

HRG
 

Mikey

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Personally I won't have any joints in my attic be they soldered or cemented and especially no sharkbite type fittings. That's why I went with pex with joints only at beginning and endings of runs.

Nice ideal, but it ain't gonna happen here. Good advice for my next house, though :).
 

Mikey

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As I was planning my re-installation, I remembered another issue with CPVC that needs to be considered. [SIZE=-1]CPVC piping expands or contracts at about 4 times the rate of copper with a change in temperature. In my case, my 80' trunk lines expand by 2.96" as the ambient termperature goes from 32°F to 120°F, whereas an 80' run of copper would expand by only 0.74". My present installation allows for this movement because the branches drop about 18" before going through sealed holes in wall plates, allowing movement in the trunk lines. You can actually see the branch drops move back and forth as the temperature in the trunks changes. If the trunks were to be dropped to the level of the plates, they would then be fixed in place, and temperature changes would generate internal stresses in the pipes. Laboratory testing and installation experience have demonstrated that the problems are much smaller than the coefficient of thermal expansion would suggest, since the stresses developed in CPVC pipe are generally much smaller than those developed in metal pipe for equal temperature changes because of the difference in elastic modulus. Nevertheless, I'm going to plan the layout of the new trunks to allow for this.
[/SIZE]
 

HomeRepairGuy

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As I was planning my re-installation, I remembered another issue with CPVC that needs to be considered. [SIZE=-1]CPVC piping expands or contracts at about 4 times the rate of copper with a change in temperature. In my case, my 80' trunk lines expand by 2.96" as the ambient termperature goes from 32°F to 120°F, whereas an 80' run of copper would expand by only 0.74". My present installation allows for this movement because the branches drop about 18" before going through sealed holes in wall plates, allowing movement in the trunk lines. You can actually see the branch drops move back and forth as the temperature in the trunks changes. If the trunks were to be dropped to the level of the plates, they would then be fixed in place, and temperature changes would generate internal stresses in the pipes. Laboratory testing and installation experience have demonstrated that the problems are much smaller than the coefficient of thermal expansion would suggest, since the stresses developed in CPVC pipe are generally much smaller than those developed in metal pipe for equal temperature changes because of the difference in elastic modulus. Nevertheless, I'm going to plan the layout of the new trunks to allow for this.
[/SIZE]

Pex expands/contracts at a rate of about 1" per 100 feet per 10 degrees farenheight. Putting gradual curves at turns can allow for this movement for short runs. For long runs, it's recommended to put a roller coaster loop in the run to allow for the movement. Also to let sagging between hangers alone and not try to straighen the tubing.

HRG
 

Dlarrivee

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I don't understand the point of this thread.

Piping shouldn't be in the un-conditioned attic...
 

HomeRepairGuy

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I don't understand the point of this thread.
Piping shouldn't be in the un-conditioned attic...
I think that is what the folks are trying to accomplish and are looking for suggestions on. Though the thread has grown branches about type of pipe to use.
 

Mikey

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Piping shouldn't be in the un-conditioned attic...

The point of the thread is that sometimes we find ourselves in situations where the piping is in the unconditioned attic, or must be placed there, whether it should be or not. We're looking for suggestions on how to manage or ameliorate the situation, and welcome constructive comments.
 

Mikey

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Pex expands/contracts at a rate of about 1" per 100 feet per 10 degrees farenheight. Putting gradual curves at turns can allow for this movement for short runs. For long runs, it's recommended to put a roller coaster loop in the run to allow for the movement. Also to let sagging between hangers alone and not try to straighen the tubing.

HRG

Right. I've seen several "proper" installations as you describe where old-school copper types blasted them for being "sloppy". I've got to admit they look sloppy compared to some of the really artistic copper installations I've seen, but as always looks can be deceiving. I'm still not 100% sold on PEX for a couple of reasons, but I'm getting there.
 

HomeRepairGuy

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I'm still not 100% sold on PEX for a couple of reasons, but I'm getting there.
The only "experience" I have with PEX is with the Uponor system that uses the expansion method for fitting connections. The expansion tool is expensive but palletable at $289 on sale at pexsupply.com, which is the cheapest I've seen anywhere for a new expansion tool. I'm going to keep my tool forever but one could "easily" sell a used one on an online site in a heartbeat and recover most of the money spent.

Had to pull 3/4" PEX tubing for trunk lines through our attic on my back & belly because of an extremely low pitch roof, and PEX is a wonderful thing. It's so quick and easy to pull with no need for joints in the attic.

Had I tried to run straight lengths of copper or cpvc, the lengths would have been restricted to about 5 feet because of the low roof height and passing the pipes through the manholes in the ceiling. I say 5' because 10' would not fit requiring cutting the 10' lengths in half. This would have required a LOT of soldering or cementing of coupler joints plus the elbows at turns. Also for copper, it would have been near impossible for me to solder all of the joints on my belly in the attic not to mention the extreme fire hazzard.

The Uponor expansion joints are really solid because the walls of the Uponor PEX tubing are so stiff plus the expansion ring that goes over each joint. At first I was very apprehensive about PEX tubing popping off fittings under pressure but after actually installing Uponor expansion joints I'm 100% confident that they will never pop off. I think the other key is to INSURE that there is NO sidewards tension on any fitting by securing all sides of joints with the proper mounts. I think this is so important because the constant expansion and contraction of the PEX tubing could act on fittings like breaking a paper clip by bending it back & forth many times. Constant back & forth tension on fittings could result in micro fractures of fittings and eventual breaking of fittings. My take on it anyway.

The other great advantage of PEX joints are when fittings are close together, like elbows or tees being 3" - 6" apart for instance. With copper, soldering one fitting can melt solder in another close fitting. With PEX, that is not a problem at all.

I guess you can tell by now that I love PEX. If you decide to try it, you might fall in love too... ;),
HRG
 
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DavidTu

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Pex expands/contracts at a rate of about 1" per 100 feet per 10 degrees farenheight. Putting gradual curves at turns can allow for this movement for short runs. For long runs, it's recommended to put a roller coaster loop in the run to allow for the movement. Also to let sagging between hangers alone and not try to straighen the tubing.

HRG

What do you define as a "long run"?
 

HomeRepairGuy

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Originally Posted by HomeRepairGuy: Pex expands/contracts at a rate of about 1" per 100 feet per 10 degrees farenheight. Putting gradual curves at turns can allow for this movement for short runs. For long runs, it's recommended to put a roller coaster loop in the run to allow for the movement. Also to let sagging between hangers alone and not try to straighen the tubing.

DavidTu said: What do you define as a "long run"?
For "my" definition, it depends on whether it is a hot or cold line, taking the expansion/contraction rate of 1" per 100 feet per 10 degrees farenheight into consideration.

For a hot water line, the water temperature in the tubing used my installation can vary from 50 degrees when cold to 120 degrees when hot. That translates to 70 degrees difference. So 100' of tubing at 70 degrees change = 7 inches of expansion/contraction. I look at my run and how gradual the 90 degree bends at both ends are and estimate in my mind how much length change can be absorbed by those curves. Bear in mind that I only use the pex hangers that allow the pex to slide within them and that I allow the pex to sag between hangers as much as it wants to. Say I'm installing a 50' run which equates to 3.5" of expansion/contraction in the hot water line. My gradual 90 degree curves at both ends can easily absorb that amount of change, along with the sag between hangers.

On the other hand, if I were to use the 90 degree bend supports made for pex at both ends, they don't allow for any expansion/contraction in the curve. So I would install one roller coaster loop in a straight 50' run for the hot water line. The cold water line is much different than the hot water line since the temperature change is much less severe. There I would just let the sag between hangers compensate for expansion/contraction changes.

Recall that this is "my" installation method that I feel comfortable with after doing tons of research and thinking on pex. Professional pex installers may use different methods so consult one of them for the "best/proper" way.
HRG
 
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