PVC to copper compression fittings - Diesel Forum - TheDieselStop.com
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post #1 of 6 (permalink) Old 11-11-2007, 11:59 PM Thread Starter
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PVC to copper compression fittings

I have a PVC compression fitting coupling into the copper water inlet line in my house. The compression fitting was used because of the fire concern in the close space involved with a sweat fitting, A year after the compression fitting was installed it started leaking. Wouldn't you know I was traveling when it happened and a flooded room occurred. I found the compression nut was loose and tightening stopped the leak. Now, six months later it is leaking again. I'm traveling again but the house sitter caught it and the leak is small so the water is being caught until I get home. Do these fittings loosen with time or is there something I don't know about using them? I do know that codes do not allow them in a sealed wall but have seen a professional plumber repair a line in a wall with one. Is my only recourse sweating a fitting onto the copper and making sure all burning wood. etc. is extinguished?

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post #2 of 6 (permalink) Old 11-12-2007, 07:35 AM
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Re: PVC to copper compression fittings

Why not use a metal compression fitting instead of the PVC one, or is there not one made that will fit? I am assuming that you are joining two pieces of copper right? I am guessing that the constant warming and cooling cycles are causing the PCV to loosen. Cool water when it is flowing and then warms while static and near the water heater.

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post #3 of 6 (permalink) Old 11-12-2007, 11:58 AM
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Re: PVC to copper compression fittings

Sounds like a job for " Sharkbite connection system ".
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post #4 of 6 (permalink) Old 11-12-2007, 12:05 PM
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Re: PVC to copper compression fittings

From copper to PVC I have always used a threaded fitting, take it out and use Male/female adapters.

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post #5 of 6 (permalink) Old 11-12-2007, 04:06 PM
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Re: PVC to copper compression fittings

I've only seen PVC Compression fittings work over time on electrical systems (and not real well until they went to fiberglass reinforcing like Carlon plastics) and would not believe they are strong enough for a pressure fitting like that. PVC has creep properties and it will not maintain physical integrity over a long time under any but a minimum of strain.

That's just one reason why they don't use PVC rod as reinforcing in concrete.....

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post #6 of 6 (permalink) Old 11-12-2007, 08:25 PM
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Re: PVC to copper compression fittings

I had the same scenario at my first house. It was on 1" copper pipe, I had to go to a plumbing supply warehouse and get 1" compression fittings that were made of brass or bronze or something like that. Worked great, never leaked, expensive, $15 each and that was 15 years ago.

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