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Is teflon tape recommended for threading plastic fittings onto metal ones? If so, how many layers? My fittings are 1 1/4" on a fairly low pressure water line.
 

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jschaben
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Is teflon tape recommended for threading plastic fittings onto metal ones? If so, how many layers? My fittings are 1 1/4" on a fairly low pressure water line.
3 months ago I would have said no. Since then I had to cut up some freshly installed CPVC to put tape on the one galvanized fitting in the whole mess. :censored:
I put about 5 turns on it when I finally got to the thing.
 

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Just call me Andrew
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Is teflon tape recommended for threading plastic fittings onto metal ones? If so, how many layers? My fittings are 1 1/4" on a fairly low pressure water line.

Yes, I would use both teflon tape and pipe dope, in whatever order you want (i put tapeon, then dope the outside).

If you are using the flimsy white teflon tape, I put a lot on, probably 6-8 layers.

If you use the good, thick teflon tape, 3-4 turns.
 

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Just call me Andrew
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I cannot speak for gas piping or air, but for normal household plumbing applications, I have never had a problem just using teflon tape, when it is applied properly. In spite of that, I still use both teflon tape and pipe dope (as do most of the pros on these boards).

Also, not sure what you are talking about (Master's compound). Is that another term for pipe dope/joint compound?
 

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Is teflon tape recommended for threading plastic fittings onto metal ones? If so, how many layers? My fittings are 1 1/4" on a fairly low pressure water line.
Many codes prohibit metal male into PVC female as the PVC female can eventually split due to the strain. They sell an adapter with a reinforced outer stainless steel ring to do this though even it is prohibited by some codes. This info and the adapter can be found here:
http://www.plumbingsupply.com/pvc.html#stainlesssteelreinforced
Click the "S x Fips" link for the info above.

Regarding using teflon tape, I always get leaks when using teflon tape alone on PVC fittings. Always! The fix I've found is to use pipe dope specifically made to be compatible with PVC, ABS and other plastic threads including metal threads. I use the Oatey Great White pipe joint compound with PTFE. Do NOT use regular pipe dope as it will deteriorate plastic.

Apply a thin coat of the Great White pipe dope on the male threads, wrap 3 turns of teflon tape on the threads, then another thin coat of dope over the tape. This method never leaks for me.

Note that there is the really thin teflon tape that is extremely hard to handle and thicker teflon tape is is much easier to handle. I use the thicker tape.

EDIT: Opps, I just noticed that you want to use a plastic male into a metal female. But the pipe dope and teflon tape info would still be applicable.

HRG
 

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Teflon tape isn't designed to seal a joint its there to lubricate it making your connection easier to put together. Pipe joint compounds do the same thing some also will seal it like blue magic, permatex etc. Always read the can to see I'd it's ok to use on your application before using it.
 

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I'm sold on tape called Blue Monster. Also their pipe dope. Neither one has failed me.
 
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