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Old 17-03-2015, 14:12   #46
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Re: Freshwater System Plumbing

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But what do I know, I was a lowly licensed mechanical and plumbing contractor for thirty five short years.
OK, I'll play this game.

I figured you were a contractor, as the pex expansion tool is a bit spendy for the typical homeowner, and you were posting quite correct information. I respect contractors as there is tons more to installing piping, then drawing lines on paper.

Myself, I'm just a lowly plumbing/piping/fire protection engineer, also with 35 years experience and have designed and specified plumbing/ hydronics for buildings, where the plumbing cost alone was $40 million+. I also do steam and chilled water and have designed large CUB's (central utility buildings) and have worked with bioitech, semiconductor as well as a few tiny buildings on the strip in vegas.

Passed the CIPE back in 83 and PE in 95 via experience. I read design manuals and manufacturers data, just for kicks and giggles. I wrote hydraulic analysis software with cad input and output and 3d rotation display, back in the early 90's, after teaching myself C/C++, just for fun. Strange girl I know....

When i rejected a submittal for piping/fittings, I would give the reasons why explaining the point of failure, in detail. Sometimes contractors would install the piping system anyway. In all cases, where i said it would fail, it did.

Sometimes it was the material that was not comparable with the system pressure. Sometimes the jointing system that created a stress riser in copper. Sometimes it was their in house engineers that missed a few things when calculating head loss.

I'm not just a blonde bimbo. I'm a blonde bimbo engineer.

I like pex. It's good stuff. But if you were to pull a section of that buried pex and tested it againsted new material, you would find that the pex that went through multiple freeze thaw cycles, where the water streached the plastic, that the yield point would be lower then for new piping. It's probably not a problem with an open system or even many closed systems, but it's not unaffected by cold either. Under some conditions after multiple freeze thaw cycles it can freeze
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Old 18-03-2015, 07:11   #47
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Re: Freshwater System Plumbing

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Originally Posted by sailorchic34 View Post
OK, I'll play this game.


I like pex. It's good stuff. But if you were to pull a section of that buried pex and tested it againsted new material, you would find that the pex that went through multiple freeze thaw cycles, where the water streached the plastic, that the yield point would be lower then for new piping. It's probably not a problem with an open system or even many closed systems, but it's not unaffected by cold either. Under some conditions after multiple freeze thaw cycles it can freeze


No argument, it will freeze, but I was unclear if I said it won't, I meant rupture due to freeze expansion. But Uponor warrants the product for 30 years, unless you run higher temperatures and pressures. Then the warranty is degraded and is clearly spelled out in the submittal and recommended specification for engineers to use in their specs.

From the contractor point of view, I have to warrant the installed and make good the damage from failure. Whereas the engineer usually has a wafflely murder clause in their spec that says I have to make it work regardless of what the spec says, and arbitrate with the manufacturer if the product fails. Not making a dig here, but I never had any failures with PEX because it was installed per manufacturers recommendations. As for the pricy expansion tool, if you go to a wholesale plumbing supply house, they will usually either rent you the tool, or agree to a buy back for a reduced price that can be negotiated.

I just think it is a good product application for a boat, and don't recommend mixing the products like various fittings, adding hose clamps and some of the other things discussed in this thread. Don't like the metal crimp rings on the Viega system either. They will corrode way before the tube ever fails in a salt water environment. Upornor uses a noncorrosive ring which I like.
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Old 18-03-2015, 09:38   #48
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Re: Freshwater System Plumbing

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Originally Posted by FlightPlan View Post
No argument, it will freeze, but I was unclear if I said it won't, I meant rupture due to freeze expansion. But Uponor warrants the product for 30 years, unless you run higher temperatures and pressures. Then the warranty is degraded and is clearly spelled out in the submittal and recommended specification for engineers to use in their specs..
We have a minor disagreement about pex. Uponor has the following line in it's limited warranty:

It is expressly understood that failure as a result of heat transfer fluid freezing within the pipes does not constitute a defect in material or workmanship and shall not be covered by this warranty..

Odd they would not cover freeze rupture in the tubing, if it was not a problem. The pipe warranty is 30 years, the fitting warranty is only 5 years. But pipe rupture from freezing is excluded. Yes the sales rep, will say that the pipe can freeze without breaking, and it can. Just not forever.

I do think we both agree that pex is good stuff and is great for boats. I have no issues at all with Uponor's fitting system, and that is high praise coming from an engineer.
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Old 11-06-2015, 15:33   #49
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Re: Freshwater System Plumbing

Just found this thread and wonder if I could get some inspiration on PEX and PB compatibility? I'm in the middle of re-plumbing my boat and as a full time live aboard I'm doing it piecemeal. I've used Sea Tech products with some success to replace the original grey PB but there are several places where it would be helpful to temporarily splice the PB directly to the PEX. Sea Tech doesn't seem to like the PB. Any ideas?
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Old 11-06-2015, 19:57   #50
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Re: Freshwater System Plumbing

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Just found this thread and wonder if I could get some inspiration on PEX and PB compatibility? I'm in the middle of re-plumbing my boat and as a full time live aboard I'm doing it piecemeal. I've used Sea Tech products with some success to replace the original grey PB but there are several places where it would be helpful to temporarily splice the PB directly to the PEX. Sea Tech doesn't seem to like the PB. Any ideas?
Have you tried mating couples. ie, have a PB to male coupling matched to a female to PEX coupling? I imagine in most cases it would be cheaper to just replace the run of PB, but if you have the pieces, this could help.
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Old 11-06-2015, 20:27   #51
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Re: Freshwater System Plumbing

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Originally Posted by Old Brit View Post
Just found this thread and wonder if I could get some inspiration on PEX and PB compatibility? I'm in the middle of re-plumbing my boat and as a full time live aboard I'm doing it piecemeal. I've used Sea Tech products with some success to replace the original grey PB but there are several places where it would be helpful to temporarily splice the PB directly to the PEX. Sea Tech doesn't seem to like the PB. Any ideas?
The best bet is to just replace the PB. In the US, you could buy a sharkbite copper slip on coupling and that should be able to join the pex and pb. rated to 80 psig or so. PEX is far superior to PB
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