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Loctite calls this goop 30534 liquid thread sealant with PTFE/Teflon. The sheer amount of oxygen required to say that could keep several people alive for a month, so I’ll take a page from Smitty’s book (the oldest mechanic I ever worked with) and call it “pipe dope.”

Essentially, PTFE thread sealant is an improved, liquid (but very viscous) version of Teflon tape with a few noteworthy advantages. It’s not direction-sensitive, so the new guy won’t wrap pipe threads backwards, and it provides a better seal thanks to its anaerobic hardening properties (much like regular Loctite). You don’t need to keep different thicknesses around for different pipe thread sizes, either. The only major disadvantage is that Teflon tape has no set time, whereas this needs to be left alone for a few hours before use. This can be inconvenient, since an awful lot of repairs are done on pipe threads.

If you can let the assembly sit for a while, a $5-$7 can is a good idea. I’ve found it’s much more reliable than Teflon tape and does a very good job making up for pipe threads’ shortcomings. Larger hardware stores and industrial supply houses are your best bet if you’re trying to lay hands on a bottle, but if that chair’s just too comfortable, there’s always the Internet.

Loctite PTFE Pipe Thread Sealant [Google Products]

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9 Responses to Pipe Dope

  1. Mrten says:

    Just get loctite 55 (or 35082) instead of the teflon tape and learn the new guy the direction to wrap. Easier, less mess and no waiting time.

  2. jeffrey immer says:

    that stuff is a certified mess ready to get on an surface and impossible to clean off, i use it when i fix sprinkler systems, and always hate it but on pvc pipes it works better than tape

  3. Davo says:

    Is that why they call it “dope”?

  4. browndog77 says:

    Pipe dope with a set-up time? Absurd. I learned many years ago (from a very old-school plumber) that the only reason for doping joints was so they could be undone in the future. It is not supposed to be a sealant, at least not in a threaded joint. If the threads don’t seal, they aren’t properly machined. The teflon infused dope from Hercules works well, on threads as well as in a compression joint. (I know they shouldn’t require it, but in smaller tubing it is a good backup in case the tube happens to get turned in the fitting after tightening)

  5. Brice says:

    I wrap in tape then goop with Megaloc. The tape helps take care of any imperfections in the threads and the goop keeps it lubed for easy thread/thread sealing. Why megaloc? Paper towel cleanup, even in carpet.

  6. shopmonger says:

    It is used as a sealant… threads on plastic are not perfect, nor are they even perfect in metals. The reality is yes, if you could machine them perfect there would be no leaking. However we are in the bulk manufacturing world because a perfect pipe with perfect threads would cost 2-3 times as much. SO Dope or tape away… I use dope on larger diameter pipe and use tape on anything 1″ or smaller. Even on car fittings, you can clean it up with some solvent…..

    Also dope does a nice job on sink trap fittings. If you want to get things back a part later and there is heat use Antiseize….


  7. browndog77 says:

    I agree with you re: sink trap fittings, and any other compression type fitting which may have to be undone in the future. As far as car fittings, if you refer to flare joints, they should never be assembled with sealant on the mating surfaces!

  8. Shopmonger says:

    Browndog77 Good point…..nothing on a flare fitting………… All you will do it create a mating surface that cannot seat.


  9. David Smith says:

    Even if the threads are perfect, there is still a spiral leak path.
    Think about it.

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