Teflon tape or pipe dope?

kudzu9January 4, 2012

I'm re-routing some 1-1/4" copper plumbing and several of the connections are threaded, including a couple of fairly beefy unions. I've pretty much always used teflon tape on threads, except for gas lines where I've used pipe dope. I've never worked on copper this big in diameter before and was wondering if there is any clear advantage to using teflon tape over pipe dope...or vice versa.

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My first question would be why are you using threaded unions instead of sweat unions(solder type)?

I would begin by examining the entire layout and eliminate as many threaded joints as possible.

The question as to whether you should use PTFE tape or pipe dope is really a matter of personal choice, providing of course that you use the correct PTFE tape and install it in the manner as prescribed by the ASTM or that you select a pipe dope that is listed as approved for the type of material that you are conveying through the pipe & joints.

Personally, I like to use pipe dope on all permanent joints, which are joints that are intended to last the life of the structure.

When making joints that will most likely be replaced occassionally, such as attaching an angle stop, shower arm or a shower head, I prefer to use PTFE tape.

    Bookmark   January 5, 2012 at 5:59AM
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kudzu9, I feel comfortable with tape at threaded drain pipe junctions. You wrote 1-1/4" copper which might be DWV but not necessarily. There is a chance you are working with supply pipe (pressurized). In that case, a lot depends on other factors like whether you intend to leave it for decades or not. It can be soldered, even if threaded.

    Bookmark   January 5, 2012 at 6:15PM
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To clarify...I'm working on 1-1/4" copper that is the cold water supply coming into my house. When it comes up out of the slab in my utility room, there is a shutoff valve and then a pressure reducing valve. The PRV was installed in a location that is terrible for access (up against the wall), and has only one union, so I wanted to reroute the line so the PRV is easier to refurbish or swap out the next time I have to deal with it not functioning right.

lazypup- I am looking to minimize threaded fittings, but there will be a couple that I can't avoid with the way the PRV is designed.

    Bookmark   January 5, 2012 at 11:02PM
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