question for the PEX experts

[drtnshtr]

I am planning on replacing the copper supply lines in my attic that freeze and bust every year with either PEX, black iron, or copper (again). Menards has the O2 barrier PEX but Im curious if it will withstand the 190-200 degree water. they also have the "gatorbite" couplers I am hoping to use. the PEX would obviously be the easiest route to go but I wanna make sure it lasts and wont bust. BTW Im using a weil mclain gold fob.

 

[drtnshtr]

I guess I should have mentioned that by supply lines I mean the lines that are in between my baseboard fins.

 

[DaveBP]

Anyway you could reroute those pipes so they don't go through the attic? PEX is a lot easier to snake through walls and floor joist bays than metal pipe.

Solve the frozen pipe problem and any heat lost from those pipes would be lost to your living space where you can actually use it.

 

[drtnshtr]

I have a cape cod home and behind the knee wall is the only route to use to go from one upstairs bedroom to the other. its a 30 ft piece im looking to replace from one radiator to the other. its pretty easy access to this attic space so really any pipe will not be hard to install.im planning on installing a thermguard this winter also.

 

[Gooserider]

I would say that you really need to look at figuring out how to insulate the lines, or possibly put anti-freeze in them... PEX is definitely the most "freeze survivable" of the available options, but freezing is definitely NOT something that is reccomended or supported by the manufacturers in any way.... I'm not sure how the O2 barrier would react to freezing, among other issues.

Even if you can't avoid running behind the kneewall, I'm sure you could create a warmer environment for them, even if it is just to create a plywood box full of insulation for the pipe to run through (Insulate the cold side of the box, and pull some of the wall insulation out on that side of the box to make it warmer IN the box...)

Gooserider

 

[drtnshtr]

I think you are right goose...Im gonna try to insulate it much better... I actually have the rest of the copper in the attic wrapped in R-19 but I couldnt get to the part that froze to insulate it. I will make sure whatever I put in their this time gets done plus I plan on getting a thermgaurd as well. not to mention I am going to run the boiler as my primary heat source this winter instead of the stoves. I just can seem to decide which to use between copper,pex or iron.

 

[Gooserider]

I think you are right goose...Im gonna try to insulate it much better... I actually have the rest of the copper in the attic wrapped in R-19 but I couldnt get to the part that froze to insulate it. I will make sure whatever I put in their this time gets done plus I plan on getting a thermgaurd as well. not to mention I am going to run the boiler as my primary heat source this winter instead of the stoves. I just can seem to decide which to use between copper,pex or iron.

IMHO that question is a "no-brainer" for this and most other applications... PEX is cheaper and easier to work with, plus, while it should never be frozen, your odds of "getting away with it" are better if it does freeze. My feeling is that for water distribution, either tap water or heating, PEX should be the "default" choice, with other materials considered only if there is a definite reason NOT to use PEX, or if there is a clear advantage for the other material....

If I was building today, about the only places I would not use pex is on Solar hot water plumbing (because a stagnating system can exceed the temp rating on PEX) or for the near boiler / DHW tank plumbing (same reasons) If I was doing an in-tank heat exchanger, I would use copper for better heat transfer properties, Otherwise I'd be using PEX...

Gooserider

 

[Tony H]

Can you run in the heated space and then cover it with some molding like wiremold or panduit . pex should be able to handle the temps just check the rating on that brand at the store.

 

[drtnshtr]

The O2 barrier pex at lowes and menards say 180 degree at 100 PSI. My thermostat on the boiler reaches 190-195...Im assuming the temp would be a little cooler than that by the time it reaches the PEX but Im not sure.

 

[Gooserider]

The O2 barrier pex at lowes and menards say 180 degree at 100 PSI. My thermostat on the boiler reaches 190-195...Im assuming the temp would be a little cooler than that by the time it reaches the PEX but Im not sure.

It should be much cooler - I think it's noteworthy that most of the stuff you read on figuring heat outputs and the like seem to use 180*F as the maximum working temperature. The other thing to keep in mind is that the "180*F @ 100 PSI is actually one of several test ratings, and that PEX can stand somewhat higher temperatures at lower pressures, such as the 10-20 PSI you will find in your boiler plumbing... My recollection is that the maximum temperature where PEX will handle any pressure is up around 275* or so, although it does start getting really unhappy around 250.

Gooserider

 

[in hot water]

Another option would be to use an outdoor reset control on the boiler. With this control properly adjusted you get pretty much constant circulation and the water should always be flowing. It adjusts the supply temperature based on outdoor temperatures. On design day it gets 180F supply, and adjusts from there downward.

Reset controls offer better comfort by reducing the temperature swings to the baseboard and can also save energy. Go to www.tekmar.com for an overview on how they work.

Pex will freeze and burst if it freezes hard enough. Watts Onix is a high temperature EPDM tube for hydronics. I've never seen it burst and it is even easier than pex to work with. But more $$

hr