I was speaking to a friend of mine today who is a plumber and also the plumbing inspector. He was saying that in radiant slab applications, it was good practice but not required by code to sleave the pex in something (like some other polyethelene) to prevent the inevitable chaffing from the concrete working on the material as it goes thru its expansion-contraction cycles with heating and cooling or from where cracks might occur in the slab.
In principle it seems to make sense but 1) Is this common? 2)Would it cut down a bit on the heat transfer? 3)How would you sleave a 300′ loop of pex? 4)Does anyone make it presleaved?
Replies
Are you sure he didn't mean just sleaves at the expansion/control joints? That's pretty common. You just slide a length of next size up pipe over the PEX where it crosses the joint.
Mike Hennessy
Pittsburgh, PA
Edit: You can slit the sleave pipe so you can just slip it on where you need it, rather than feeding it all the way from the end of the pipe.
Edited 12/8/2008 7:48 am ET by MikeHennessy
another case of a little bit of knowledge is a bad thing.. Concrete doesn't shrink and expand enough to cause a problem. Where expansion joints will be put in a little piece of sleeve can be used for whatever movement might take place. Expansion and shrinkage is much more common underneath wood but the very means of holding the pex in place takes care of that.
Edited 12/8/2008 9:02 am ET by frenchy
What they were refering to is the short little pvc elbows that are used where each tube enters or leaves the slab. They look like pvc conduit long sweep elbows. They perform two functions: 1) to protect the surface of the tube at the concrete pening where abrasion can occur ans 2) make a nice turn from vertical to horzontal without kinking. They are a good idea, but not a necessity. I would use them in any slab I put tubes in. The only cover about a foot or so of the tubes.
Edited 12/12/2008 2:27 pm by Tim