HomeRepairGuy
Member
Did you choose cpvc over pex in the attic? Just curious if you did.I'm about to undertake the same project as Mikey—slab house in Southwest Florida; failing copper; running new cpvc supply through the attic.
HRG
Did you choose cpvc over pex in the attic? Just curious if you did.I'm about to undertake the same project as Mikey—slab house in Southwest Florida; failing copper; running new cpvc supply through the attic.
Did you choose cpvc over pex in the attic? Just curious if you did.
HRG
CPVC is the plan.
With the possibility of freezing, wouldn't pex be better than cpvc?
"Insulating properties of cpvc"!? Listen to the experienced tradesmen guys.
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.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.
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.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.
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.
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.
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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.I don't understand the point of this thread.
Piping shouldn't be in the un-conditioned attic...
Piping shouldn't be in the un-conditioned attic...
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
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.I'm still not 100% sold on PEX for a couple of reasons, but I'm getting there.
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
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.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"?
This is awkward, but...
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