pex expansion when heated

mikedo

does heat pex expand like copper when heated. I'm worried about noise when used in a baseboard system if the pex is strapped tightly

kcopp

Yes it does. In fact about 4 times as much. There is a product the Viega makes "Fostapex" that has a lower expansion rate.

GroundUp

Pex expands 1.1" per 100 feet per 10 degree rise
Copper expands .125" per 100 feet per 10 degree rise

Almost 9 times as much. FostaPex was some awesome stuff, but has been discontinued. There are other brands of pex-al-pex (a layer of aluminum sandwiched between 2 layers of plastic) which would serve a very similar purpose in reducing thermal expansion.

PAP expands .3" per 100 feet per 10 degree rise

Jamie Hall

As noted, it will expand. If you don't allow for the expansion --bends, joints, it will give you much grief.

mikedo

thanks

Dave Carpentier

What happens inside a slab, with all those little sharpish edges against the pex ?

Canucker

Dave Carpentier said:

What happens inside a slab, with all those little sharpish edges against the pex ?

Nothing. The pex encased in concrete doesn't move. However, it needs to be sleeved as it exits or enters the slab for the reason you're thinking of

Dave Carpentier

Hmm, I'll have to check if we used sleeves. There's metal guide things that turned the pipes up 90deg. Im not sure if they went all the way around the pipes though.

Jamie Hall

If the PEX is totally restrained in the slab it will squish. It won't like it, but it will. Unlike copper, the forces aren't great enough to crack the slab.