Transition from PVC to brass?

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Old 01-22-10, 12:43 PM
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Transition from PVC to brass?

edit: OK i did a quick search and found several previous threads on this exact topic. I'll try a threaded male pvc pipe to the threaded female brass with tape and dope.
 

Last edited by txnoob; 01-22-10 at 02:05 PM.
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Old 01-23-10, 07:55 AM
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Use tape OR dope, but not both.
 
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Old 01-26-10, 07:07 AM
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So on pvc to brass, just one or the other huh?

Is it because of the hardness of brass compared to the pvc that could cause damage to the pvc?

In the past I've always used tape AND dope on brass/brass, brass/copper, copper/copper.
 
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Old 01-27-10, 08:53 AM
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I use tape on plastic and dope on metals. When transitioning from one to the other, I use tape.
 
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Old 01-28-10, 12:53 AM
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I disagree with my friend Lefty and ALWAYS use a paste type thread sealant when assembling threaded pipe of different materials. Using only Teflon tape I have ALWAYS had leaks with plastic and metal.

Be sure that the paste you use is approved for BOTH piping materials AND the medium flowing through the piping.

Many pipefitters use BOTH Teflon tape AND a paste (or semi-liquid) thread sealant.

After more than thirty years of use my personal opinion is that Teflon tape has only one advantage, it is clean and easy to use. Unfortunately the biggest disadvantage to using Teflon tape is that on just about anything other than metal piping running potable water the Teflon tape alone will likely leak.
 
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Old 01-30-10, 08:24 PM
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Furd, you make good points, and I would tend to agree with you EXCEPT in the past 6 months I have taken apart a couple of old threaded joints where plastic pipe (ABS and PVC) were involved, and whoever put them together used some sort of pipe dope, and it appeared as though the dope that was used damaged the threads on the plastic pipe. It looked like a cancer attacking the plastic. Who knows what they used 15 or 20 years ago, or if it's even still available. But it makes me leary about using dope in contact with the plastic.

Wrap the plastic with tape and apply dope on top of that -- I'd be fine with that. It keeps the dope away from the plastic. Or just use teflon paste and forget the tape. Best of both worlds!!
 
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Old 01-31-10, 02:34 AM
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You're absolutely correct, Lefty, that's why I stress that the sealant MUST be listed as compatible with both types of pipe. Even some Teflon pastes are specifically listed as NOT safe for plastic piping.

In the past most pipe joint sealant contained some kind of petroleum derivative. Petroleum and plastics rarely are compatible. Although it will take years even the plastic gasoline cans will get hard and crack.
 
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