Hi all,

Zurn best practices says to add 1/8" per foot of pex for expansion. They say to either loop or off-set 12" in bay.

Is this applicable to potable hot and cold, and heating applications?

most pex will expand 1.1" per 10 degree rise per 100 feet of length. so if you install on a 60 degree day and you're running 150 degree water through it, that's a 90 rise, or 9.9" per hundred feet, or about 1/10 of an inch per foot.

so 1/8" per foot is definitely worst case. and it's not particularly applicable in potable applications, though if you install on a 90 degree day and you run 50 degree water through it, you might have issues on long runs..

I'll throw in a little tidbit here. When I installed my wood-fired, outdoor boiler years ago, I missed a small part of the instructions that said to leave extra pex and hook the underground pipe up above ground first and run the system through a heating/cooling cycle. Then cut the pex to length and bury it. The reason for doing this is that the pex initially expands upon heating and shrinks a LOT upon cooling. After the first cycle, the pipe will expand and contract - probably by Rob's formula. But that first cooling cycle shrinks the tubing and never returns it. I lost probably a foot of pex in 50 or 60 feet. Shoulda read the instructions a bit more carefully.