After the fact kinking

NRT_Rob

has anyone ever seen kinks show up in pex that was not there during an installation, but happened days afterwards? I've seen it and we're trying to figure out a cause. application is pex in heavy gauge joist plates.

Greg Maxwell

Kinking

What type of pex? What water temp? What spacing? Location of kinks?

NRT_Rob

thanks for replying Greg

kinks at the loop bends, between 6" and 9" o.c. water has never touched the system... happened on 2 projects installed this year, one in the winter and one in the summer.



I would be very interested if anyone else has ever seen it. Personally I've never heard of kinks appearing AFTER an install.

Greg Maxwell

Kinking

It it Pex A or B? Also. what diameter. Pex B is much less flexible. We have been using Rehau (pex A) for around 15 years, and I have never heard of anything like that.

NRT_Rob

PEX A

I've never seen anything like it in 15 years either. I won't note the brand yet because we don't know if it's the pipe. but unless I can find some other examples of it happening to other brands....

Greg Maxwell

Kinking

Pex doesnt kink itself. I suppose if there is too much stress placed on the tube on a return bend, there could be a reason to crimp. There has to be a common denominator. Spacing issue maybe? Could there be some kinking going on during install, that may be getting accidentally over looked?

NRT_Rob

possibly

but having never seen this in 15 years I am having a hard time thinking that two different installers within six months of each other are making the same mistake. and I don't see any issue with the on centers.. the pipe should be able to handle what it's being asked to do in that respect.

Greg Maxwell

Kinking

Same brand of pipe on the jobs?

NRT_Rob

yes sir

and one installed in the winter, and one in the summer, so not even similar temperature conditions.

Greg Maxwell

Kinking

Is it pex A or B

NRT_Rob

it is

pexA

Alan (California Radiant) Forbes

Kinking

I've never heard of self-kinking PEX before.  This is a new one. 



Have you contacted the manufacturer?

LarryC

Straw grasping

Was the kinked portion of the tubing near the edge of the supply reel?  My thought is that perhaps some sort of damage happened to the tubing while it was still on the factory reel.

Did both tubes come from the same shipment from the factory?  What are the commonalities of the failures?

Same manufacturer?

Same lot?

Same wholesaler?

Same distributor?

Same type of location for the failure location?

Same people at both job sites?  Not necessarily heating industry people, but someone else messing with the installation.

Any indications this was deliberate damage?

LarryC

Double post

kcopp

were the bends.....

done opposite the radius coming off the reel?.... in other words if it had a Left hand bend to it was it torqued back to the  Right hand... the radius is less then. Pex has the memory aspect.... it will eventually go back the way it was extruded. kpc

NRT_Rob

good questions

same MFG, not sure of the lot. Same location for failure, no common people on either project and zero chance of deliberate damage.





I think it boils down to: if no one else has ever seen this before, it's gotta be the pipe. The installation method has been used (heavy plates in joist) for many thousands of installations out there... There are no other common factors.

NRT_Rob

oh yes

they are not seeing anything on their end.



Even if we broke the minimum bend radius, I've never seen pipe survive it only to kink later. that's the part that is spinning my noggin.

NRT_Rob

good question

I have no way of knowing that. but even then... wouldn't it kink immediately?

kcopp

maybe...

maybe not.  Uponor pex rings don't shrink back right away. Just a thought.

NRT_Rob

well, by "immediately"

I mean in minutes, not weeks.



my theory so far has been that it survives the original install but then conforms and weakens... but I've never seen that occur in any pipe.

pipe4zen

plates

you mentioned plates,

Heavy gauge or light, did the kink occur at the end point of the plate, or did it kink in in the middle of the bend?

NRT_Rob

heavy plates

kinked halfway through loop head bend.

pipe4zen

turns at plates

I'm sure you have photos, and respect that you may not want to share just yet.

Another theory , was the bend made some distance from plates say 6"-12" from plates,tubing, then start turn.

Even though you stated not active loop at time of kink, there must be some minimum expansion/contraction always occurring from ambient air fluctations. My guess tube may not be allowed to move at end of run. I think plate manufacturer's require 12" at end of joist?

NRT_Rob

loops were free hanging

and it occurred at the "peak".



some loops exited the end of the plates and made a regular bend around



some pop out early and make the bend without shooting out of the end of the plate... the plates are tight enough to allow for that.



the plates are also tight enough that the only movement is in unenclosed pipe... so just the bend itself, in these cases. pipe in the plates doesn't move.

hot_rod

are the bends

really close to where the tube comes out of the plates. I've kinked tube when the loop ends are pulled too close, but it happened during the installation.



How do you know when they kinked? Pictures of the original installation?



hrt

NRT_Rob

not really

kinks are at the "Peak" of the loop bend... equidistant from the two plates. right where you would expect a kink if you bent it too tightly but we shouldn't be too tight.



I have 2 installers giving the same story though, no kink during install, checked it out later and there was a kink. So I think the report is reliable.

STEVEusaPA

I don't think it was an install issue

Although you could slightly kink it without immediately noticing, especially when your pulling the long loops into the bays.  How about the moisture content of the wood you're attaching the plates to?  Was it new construction, or in the case of the summer install, lots of moisture that was in the wood without the benefit of the AC running?  Otherwise, I'm just as perplexed.  Like you said, you do it the same way a gazillion times, then this.

Greg Maxwell

Kinking

I think that the tubing was stressed at the apex of the bend. The likelyhood of pex "a" to kink by itself is extremely low. My bet would be kinking on install.