coupling copper and cpvc

I have to join 1/2 inch copper to 1/2 inch cpvc and the 'clerk/salesperson' at Home Depot sold me on using the Push N Turn couplings. Well I've now used up 3 of them (they're non reusable items)and I still have a leak on the cpvc side ! The copper side seems fine. It's become a waste of money and time. Is this 'do-able'and am I missing a trick?
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Get a CPVC female thread adapter - make sure you get the kind that has a neoprene gasket at the seat of the fitting - and a copper male thread adapter. Sweat-solder the copper adapter on to the copper pipe, wait for it to cool, coat the threads with pipe dope, and screw the plastic adapter onto it. Finally, solvent-weld the plastic pipe into the adapter. No leaks!
--
Regards,
Doug Miller (alphageek at milmac dot com)
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I have read that it is customary to use a male plastic thread adapter and a female copper thread adapter. The idea is that since copper is stronger than plastic, if you use a female plastic part, inserting the male copper part may stretch the female plastic part, causing a future leak. (Plumbing a House, by Peter Hemp, Chapter 4 "Joining Plastic Pipe to Metal Pipe")
To the OP, for a picture of a female copper thread adapter, see
http://images.orgill.com/200x200/6563142.JPG
For a picture of a male CPVC thread adapter, see
http://www.hardwarestore.com/media/product/245407_front200.jpg
Cheers, Wayne
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Yes, I've read that, too - but I have *experienced* that male plastic to female metal joints almost _always_ leak, and male metal to female plastic with neoprene gasket _never_ do.
--
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Doug Miller (alphageek at milmac dot com)
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frankg wrote:

I have no idea about the "Push N Turn" couplings but just yesterday I successfully connected two lines of 1/2" copper to 1/2" cpvc using compression fittings that I picked up at the local hardware store. Just hand tighten them at first and if you have a leak then "wrench" them a bit, but don't go overboard.
Don
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Does your local code even allowes thoses?
If they don't leak now, they will leak later. Solution is cheap & easy. Get male & female / copper CPVC adapters sweat or glue each side. Problem solved forever. ( and guess what, they cheaper )
P.S. HomeDepot will try to sell you new presoldered copper adapters. They will leak when used by newbies. Avoid them.
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You folks said - "Get a CPVC female thread adapter - make sure you get the kind that has a neoprene gasket at the seat of the fitting - and a copper male thread adapter. Sweat-solder the copper adapter on to the copper pipe, wait for it to cool, coat the threads with pipe dope, and screw the plastic adapter onto it. Finally, solvent-weld the plastic pipe into the adapter."
and also,
" Get male & female / copper CPVC adapters sweat or glue each side"
Do you maybe have a link to what these look like so I can recognize them in the store ?I did a google search but didnt find anything
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Copper male-thread adapter looks like this: http://www.lowes.com/lowes/lkn?action=productDetail&productId282-137-604
I can't find a picture on-line of a CPVC female-thread adapter... but if you go into the store, you shouldn't have too much trouble finding them.
--
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Doug Miller (alphageek at milmac dot com)
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I don't know what a Push and Turn coupling is, but as the other posters have said, the best solution is to use the appropriate male/female adapters.
DO NOT use the CPVC "female" adapters that have the threads cut into the plastic. I don't think they are allowed by code anyway. I've tried them in the past and when the metal "male" adapter is threaded into the CPVC "female" adapter, it cracks the female adapter. Happens almost every time, no matter how careful you try to be.
You could use a MALE CPVC adapter threaded into a copper FEMALE adapter. I've done this a few times and have made many connections that work fine. However, the expansion rates of the two materials is apparently quite different and over time the connection can start leaking. I haven't experienced that personally, but I can see how it might happen.
The best solution is to use a "CPVC Transition Union" specially made for the connection. They have a brass fitting on one end, a CPVC fitting on the other, a neoprene gasket in-between, and a threaded piece that holds the two halves together. These come in several configurations, with male or female fittings on the metal end, or even brass drop-ear elbows. I've used a LOT of these fittings. They're easy to install, and I haven't had a single leak from any of them.
Here are couple of examples of the transition unions: (watch the word wrap)
http://www.cornerhardware.com/item_218994/Genova/Genova/1/2-Transition - Union/item.html
http://doitbest.com/shop/product.asp?mscssid CJ0036RMMQ8GKQ660L8VNFSRSD6F 09&dept%5Fid92&skuF5275
These fittings are usually located with the CPVC fittings in the home centers. The only real negative is the price. They cost a few dollars each. But, they're worth it.
Anthony
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You must be doing something wrong - that's *never* happened to me, and they never leak, either.
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Doug Miller (alphageek at milmac dot com)
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I "have" made many successful connections with female threaded CPVC adapters, but I've also had enough failures that I know not to use them.
The PROPER way to make these transitions is with a TRANSITION UNION. They are strong, ensure leak free connections, and accomodate the different thermal expansion rates of the dissimilar materials.
Anthony
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Use cpvc and copper threaded adapters as per previous posts. DO NOT use pipe dope on ANY plastic threads. Many pipe dopes will soften plastic, causing a leak and possible catastrophic failure. Use several wraps of teflon tape instead. The ONLY pipe dope I have seen that does not soften plastic fittings is Gasola. If you get it on your clothes, it will not wash off. Also, when you solvent weld the pvc fitting, make sure you use PVC cleaner (also called primer) on the CPVC pipe and fitting per the directions on the cans of glue and cleaner. If you don't, the plastic joint may fail in a couple of years.
Stretch
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Make sure you use CPVC glue too, NOT regular PVC glue.
Anthony
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The only thing I could find that resembles the 'transition union' or 'adaptors' described here in this thread, is a unit made of two coponents - it has copper on one side that has to have the 1/2 inch copper pipe soldered into it, and this copper has a male thread on it's other side. This male thread is joined to the second component - a brass (I think it's brass) Female thread ring that is similar to the end of a hosepipe, which has a washer and the cpvc piece within. The cpvc must be glued to the 1/2 inch cpvc pipe.. Hope I've described it clearly enough - this is the only configuration I found - no elbows etc. Sounds like the right thing ?

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Frank,

That sounds like the proper fitting. The coupling ring does indeed look a lot like the end of a garden hose (though types with plastic rings are also available). Ironically, I haven't seen the type with sweated copper fittings around here, but I know they exist. All of the ones I have seen have threaded brass ends on the copper side.
Remember to disassemble the transition union and solder the copper piece on first. Otherwise, you'll melt the CPVC side and/or the gasket.
Also make sure you slide the coupling ring over the pipe on the proper end before soldering/gluing the fitting in place. You don't want to discover you left out the ring or put it on the wrong side after you've assembled everything... :) And don't forget the gasket when you put it all together.
Anthony
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My local Aubuchon Hardware store carries compression fitting that go from copper to CPVC/PEX/PVC. They are a gray colored plastic. I don't have the manufacturer's name as I tossed the package after I installed them I think this sis the one http://www.pexconnection.com/categories.php?catID=3 .
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Anthony caught stretch's error: "make sure you use PVC cleaner (also called primer) on the CPVC pipe and

Make sure you use CPVC glue too, NOT regular PVC glue.
Anthony
Sorry, I meant CPVC primer, although most primers(cleaners) work for both PVC and CPVC.
Stretch
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thanks everyone - the 'transition union' worked out great

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