pex pipe burst in radiant heating system

Paul Pollets

there has been defective Plasco piping (with premature failures) in the Seattle area that is the subject of several lawsuits locally. If the electric boiler is running at 160+ without a mixing valve, the piping system is under duress. The sample could be tested by a forensic lab to determine the cause of failure.

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Derek_6

pex pipe burst in radiant heating system

I had to repair a section of pex that had burst in a radiant heating system recently.I have not seen it happen before and at this point do not know whether it is a faulty piece of pipe or some other reason.The system has a electric boiler and runs at 15 psi, the pressure relief was working although I have replaced just in case.This is not a new system, probably between 5 and 10 years old, and the piping is run in between the joist spaces.
Have any of you come across a problem like this?

Al Letellier_9

burst PEX

What brand was it? Did it freeze? Maybe you should seek out the rep of the manufacturer. If it burst with no outside influence or circumstances, they may want that piece to find out what happened.
Haven't had any trouble with any pex that we didn't know or couldn't figure out what happened. Have never seen any PEX just let go for no reason.

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leo g_13

Just curious

is the tubing attached to the underside of the floor, or to the side of the joist? What temp is the boiler set at? Is there a safety high limit on the system?

Leo G

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Derek_6

burst

Here is a link photo of the piece I cut out http://i37.photobucket.com/albums/e58/xuklad/burstpipe002.jpg
The pipe is stamped "plasco oxyguard"
The operating thermostat was set at 140 , I have not had the boier running again yet(I am going back tomorrow)so do not know if that is working properly or not.It is an Arco boiler, is has a high limit but no indication of what temperature it is set at.
The piping is clipped to the side of the joists.
My gut feeling is that it has overheated somehow, but the piping does not look damaged. I will see what happens when I turn thae boiler back on.

kevin coppinger_4

that sure....

looks like delamination from overheating to me....must have found a weak spot in the cross linking...kpc

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Brad White_49

My gut says

the failure might have been a spot of external overheating such as a pass of a torch..the thinning walls -the "smile" at the split, some apparent surface puckering to the left, leads me to think that. Created a weak spot then the burst force was perpendicular. Nothing you described as far as temperature and pressure, if it was kept as such, falls outside of acceptable operating parameters. But with a weak spot anything is possible.

Just a guess.

Also the inside looks chock full of black iron. May not have contributed but just an observation.

Brad White_49

Paul, is Plasco

a local house-brand? Curious why the failures are indiginous to your area. Any outcomes? The failure does seem so abrupt and local. Agreed, forensic testing is the only real way to know for sure; my guess was just a guess. Plastic equivalent of a ductile fracture...

Paul Pollets

Plasco

was a Canadian PEX company purchased by Uponor in the mid 90's and sold a few years later. Some pipe was extruded locally near Seattle (or so I'm told) B-Pex. I'm not sure where the composite pipe was made.

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Tim Doran

Ductile Failure

That burst is described as a ductile or stage 2 failure and is usually associated with high temperature and/or pressure. Most often a combination of the 2. As you can see that plastic was very elastic and stretched pretty far before the burst. Any can lights or other heat source around?

Tim D.

Brad White_9

Exactly

I we both see the same thing, a ductile failure. Kind of stretchy, an errant torch-pass. (Is there such a thing as a brittle fracture with PEX, even at low temperatures?) But the core thinking we agree on is that it stretched before failing.

Tim Doran

Brittle Failure

These can occur when something allows the plastic to creep at a molucular level. Usually this is a breach in the cross link that allows the molecules to escape or shift to another place. This can be the actual plastic molecules or it can be one of the many different compounds used to enhance the raw plastic. Other factors have to be present and usually involve water quality or lack thereof. UV can also accelerate this creeping thing.

Tim D.