Steel/CPVC transitions


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Old 10-15-05, 07:30 AM
fuddy
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Steel/CPVC transitions

What's the most secure transition from existing threaded steel pipe to CPVC(hot water, pressurized lavatory supply)? I'll be tee-ing off from an existing union in the steel piping. Thanks.
 
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Old 10-15-05, 08:04 AM
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fuddy, Welcome to the DIY Forums.
If I am understanding your question correctly, a CPVC "male iron pipe adapter" is what you want. It has threads on one end and a glue socket on the other end. Using teflon tape or pipe dope compound, you screw the adapter into the steel union and continue from there with glued CPVC pipe. Good luck with your project.
 
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Old 10-15-05, 08:36 AM
fuddy
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An almost instantaneous reply! Wowee! I've heard that, with this method, the different responses to heat & cold between the two different materials weakens the seal at the threads. So this is no problem then? I just have visions of the threaded transition blowing apart after my 9 year old self-propelled creature uses the lavatory & me coming home to a flood.
 
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Old 10-15-05, 09:35 AM
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You should have no problems. As a sidenote, some plumbing codes do not allow a female CPVC adapter while it is okay to use the male adapter. I have to guess that the female adapter has the problem you alluded to with breakage. As in all plastic type plumbing installations, proper support is necessary to prevent unnecessary movement of the pipes.
 
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Old 10-15-05, 10:36 AM
fuddy
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O K, that's what I needed to know, majakdragon - thanks a whole bunch.
 
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Old 10-15-05, 11:46 AM
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Wel, the best advice about transition to CPVC is that this is a bad idea. But that doesn't solve your problem. You are stuck with the CPVC.

As already mentioned, plastic female threade fittings should be avoided. Even a little overtight, and they can crack. SO you should be using a female steel adapter, and screwing a male threaded CPVC piece into that.

Even on a male adapter, overtightening is the most frequent problem in any plastic pipe. Most plumbers recommend using two to 3 wraps of white teflon tape, AND a coating of a pipe compound specifically recommended for plastic. This will be a teflon paste, as opposed to an oil based compound.

The fitting should be snugged up good by hand, then one half to one full turn by wrench. No more. The softness of the plastic and the lubrication of the tape and dope, will allow you to continue tightening and it may not "feel" all that tight, but the plastic is being deformed.
 
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Old 10-16-05, 05:52 PM
fuddy
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Thanks, 594. Isn't there an adapter that incorporates a manufactured transition between the steel & CPVC within the adapter? I'm thinking I saw something like that, somewhere.
 
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Old 10-16-05, 08:44 PM
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Yes. They do make a transition fitting that goes from either IPS female or male that is brass with a transition to CPVC with the union consisting of a 3/4" garden hose thread connection with a rubber washer making the water tight bond.

In no way can this transition fitting be concealed in a wall or covered over. These fittings are commonly found where cpvc is found to transition to copper or galvanized, anything with IPS threads.
 
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Old 10-17-05, 10:58 AM
fuddy
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Thanks - found some valuable advice here - I'm confident I won't screw anything up now.
 
 

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