pex fish through inside wall, does it need to be fastened? quick question please

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Old 12-17-13, 07:03 PM
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pex fish through inside wall, does it need to be fastened? quick question please

I am going to run some 3/4 heating pex through an interior wall so I can heat my bonus room. do I have to fasten it in this wall to a stud or can I just fasten it in the crawl space and in the attic where it comes in and goes out? I don't want to tear up my sheetrock if I don't have to just to fasten it. When the pump goes on does it send so much pressure that it will eventually knock the sheetrock loose? I have 9' walls, is this too much length without a fastener. thanks so much. matt
 
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Old 12-17-13, 07:13 PM
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I have seen one leak where unrestrained PEX moved back and forth with pressure changes and eventually cut itself on a sharp steel truss bracket. My guess it took six years but it did eventually cut through. The homeowner did mention hearing a clunk sound when the pump would cycle on and off but didn't think much of it.
 
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Old 12-17-13, 07:24 PM
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thanks, I guess I could cut out 2 or 3, say 6 in pieces of sheet rock every 3 ft or just one in the middle, to fasten it. or I could just go out the rim into my garage and up to the bonus room. so either i go up through interior wall and across attic about 10ft, or go through crawl space 10 ft across, through rim joist into garage, then up to bonus room. either way I will black foam insulation in garage or attic. Thanks for your quick reply
 
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Old 12-17-13, 07:54 PM
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Can you make a big enough hole to push the tubing WITH INSULATION through the cavity? Maybe tape the insulation on in a few spots along the length so it doesn't come loose as you are fishing it through?

When the pump goes on does it send so much pressure that it will eventually knock the sheetrock loose?
No, I don't see how that could ever happen.

I have seen COPPER tubing get 'sawed through' by a baseboard bracket. Took about 12 years but eventually from the expansion and contraction it cut a pinhole in the copper.
 
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Old 12-17-13, 08:13 PM
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Actually, that's what I had in mind, to put insulation over both and tape them together. I am pretty sure they will both fit like this when I was building the home, I had scheduled the sheetrock guys to be there on a certain day and with a full time job, I just had my dad drill me holes on both bottom and top plates and put a pull string through for this thing. I should of just had him run the pex through and fasten it. but I didn't, oh well
 
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Old 12-18-13, 05:55 AM
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The problem with pex is it's thermal expansion.
As the water temp goes up, so does the length of the pex, this leads to it flopping around in the space. It could easily tap the drywall or stud as it grows.

I would be inclinded to fish a straight length of Type L copper thru the wall section and then transition back to pex at each end. You could also use PEX-AL-PEX, or Watts Onyx.
Both have minimal thermal expansion, with onyx being practically 0.
The down side is cost, onyx is going to be expensive in the 3/4" sizing, and Pex-Al-Pex can be a PITA to work with and the fittings require special crimpers.
 
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Old 12-18-13, 06:53 AM
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TO, wouldn't you tend to think that if the PEX is 'wrapped' with a foam insulation that this would tend to eliminate issues you speak of?
 
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Old 12-18-13, 06:57 AM
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Wrapping PEX in insulation will not stop it from expanding but it would protect it from being cut and from making a banging sound. Around here using copper would be an option on city water but throughout much of the county the well water quickly corrodes copper so I avoid it whenever possible.
 
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Old 12-18-13, 08:31 PM
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once the water sits in a closed loop system, the water should not corrode the copper.
Never ever seen Type L with holes in it due to corrosion. Perforated due to screws yes :-)

Exactly, the insulation will not stop the flopping around of the pex. It may stop it from tapping the walls or studs.
 
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Old 12-19-13, 06:57 AM
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Exactly, the insulation will not stop the flopping around of the pex. It may stop it from tapping the walls or studs.
I guess my question would be:

If the insulation stops any noises, and protects the pipe from abrasion and eventually leaks, then is there any down side to not ripping out the 'rock to fasten the tubing to something?

Who cares if it moves around a little as long as it doesn't hurt itself or annoy people with noises?
 
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Old 12-19-13, 04:43 PM
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I suppose it's ok...
if you like floppy pex.

:-)
 
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