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Old 02-09-2005, 11:56 PM   #1
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CPVC vs. PEX?

Ok - I went to the trailer today. Found some new stuff for me to do....
1) My last waterheater installation had some "adjustments" to the copper piping to get everything to line up - it seems to have weakened the line, and now it's shared off a tee on the cold line side. Oh yeah, and for some reason my heater does not fire up (again, separate post).

2) Found my old PAR may have given up the ghost (I left the pump switch on). Thankfully not too much water in the trailer! Separate post on how to test it once I get it out.

3) I think I may have discovered a few more new plumbing leaks, which begs the question.....


I think I'm going to go whole hog and just replace all the copper (my drain line valves are leaking too) with whatever I decide to go with. Rebuild my PAR (as long as the pump still works), and ... and....and...(I'm really telling myself that that new CCD IS TOO EXPENSIVE).

I did a search and have been reading about PEX (I need to rent some tools) vs. CPVC piping. Vibration(?) seems to be the big question. However, I also know my drain pipes are also plastic (ABS). What's the difference between CPVC (which is semi ridgid) and PEX? I'm not a good solderer, so copper is out. Anybody around Seattle have some PEX tools that I could borrow?

Marc
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Old 02-10-2005, 12:16 AM   #2
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Marc,

I went through this very thing a couple of years ago. The conventional wisdom is PEX because that is what current RV manufacturers use and it is somewhat freeze *safe*.

The downside as you say are the special crimping tools needed. These can be replaced with Quest compression fittings of various flavors. I found our local Lowe's to have everything. Home Depot did not.

Having said all of this, not one to follow the crowd, I went with CPVC.

My reasons were, cheaper, smaller fittings compaired with Quest, availibility, and glued joints instead of compression or crimped.

I liked working with it. The past two seasons it has proved to work great.

You can see some info on what I did on my website.

http://www.ldservice.com/tim/airstream/plumbing.htm

Good luck with your decision!
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Old 02-10-2005, 08:57 AM   #3
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My mechanical engineer brother says that cpvc does not take vibration and movement very well and freezing not at all. PEX, on the other hand is scarcely affected by moving stresses and has some ridiculously high tolerance to freezing. However, the fittings are still going to fail if they freeze, even if the tubing is fine.

There are three ways to connect PEX, of which I am aware. Qest brass, Qest plastic, and Flair-it plastic. Since I didn't have access to the tools either I used both Qest and Flair-it plastic. I have not been very satisfied with the Qest, but the Flair-it fittings are great.

If I was to start from scratch today I'd suck it up and buy the $100 tool and use the brass fittings. They will be the fastest to assemble and slightly less expensive overall.

Good luck,

Mark
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Old 02-10-2005, 04:57 PM   #4
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I have a deal with my plumber. I'll cut everything and fit it together and he will come by and do what the fancy tool does. An hour of his time will be well worth it. I'll know it was done right with the best fasteners. Since the fittings will all be higher than the tubing they should not freeze even if the system is drained less than perfectly. Assuming the water pump is also off the floor, ect, ect,

I just cann't understand why designers put fittings in places you cann't easily reach and at the lowest point in the system to save 6 feet of copper pipe.
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Old 02-10-2005, 05:10 PM   #5
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IMHO, PEX with Flair-It fittings is the only way to go. Easy to install and no special tools needed. Had one small trickle when I first turned on the pump. Tightened it and that was it. No leaks - clean and simple. Woudl I do it again? You bet and I will on my next vintage unit.

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Old 02-10-2005, 08:16 PM   #6
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How do they work?

I looked at a website - how do the flair fittings work? Do they just press over the barb and then clamp with a hose clamp? I guess I'd better check out the local rental centers too.

But again... how DOES CPVC get affected by vibration. I could understand if it were flexing over an 1" over time, but really, the trailer doesn't move that much. Even the ABS pipes seem more brittle to me. Water hammering in a house makes more firm vibration in my mind then just driving around. It is still flexible over it's length, right?

Marc
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Old 02-10-2005, 08:37 PM   #7
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Quote:
Originally Posted by 3Ms75Argosy
I looked at a website - how do the flair fittings work? Do they just press over the barb and then clamp with a hose clamp?
No, you put the cap on over the tubing, press the barbed fitting into the tubing, then tighten the cap down onto the fitting. It is very secure.

Quote:
Originally Posted by 3Ms75Argosy
But again... how DOES CPVC get affected by vibration.
I suspect that stuff in our coaches moves around more than we think - even if Andy has balanced our running gear! In my coach there is a run under the floor from the streetside that comes up under the shower. The tubing came up through a hole in the floor, then through another hole in one of the shower pan supports, and then up into the area under the bathroom sink. It developed a leak due to the fact that the plywood in which the hole was cut sawed the old polybutylene tube through on one side. Granted, this took about 15 years.

Mark
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