Posting a message to the forum will remove the above advertisement
  1. This site uses cookies. By continuing to use this site, you are agreeing to our use of cookies. Learn More.
  2. Checkout our Plumbers Insurance area - heavily discounted Public Liability Insurance and Van Insurance specifically designed for plumbers.

Discuss Seeping threaded fittings... *stainless/brass plastic* in the Plumbing Forum area at

  1. Deuce

    Deuce New Member

    Hi all, just joined to try and get a definitive answer on this!

    When connecting threaded fittings, metal of plastic, what single application thread seal product works best?

    We have tried:
    • PTFE + silicone. Virtually always seals but will seep if agitated after cured.
    • PTFE with Fernox general purpose thread sealant, still sometimes seeps on larger threads 1" or over, and can also fail if agitated after cured.
    And also just silicone on some ABS/PVC threaded fitting, as advised by the manufacturer (PTFE can react apparently).

    We have to quite often adjust the layout of the kit we assemble and we need to be able to make and break threaded connections relatively quickly, cleanly and not waste time re-working seals as we currently do sometimes. We use threads up to 2" max.

    Cost of solution is really not an issue as it's having way more impact on time than we can afford as it is. We also need to be really confident our kit will not leak/seep at all.

    I have been looking at Loctite 5776 (LOCTITE 5776 - Thread Sealant - Loctite) and wondered if anyone here had used it, or similar, or could reccomend another product.

    I guess as it's so important we don't get leaks, products used reliably for gas might prove most appropriate?

    Many thanks in advance

  2. ShaunCorbs

    ShaunCorbs S. Mod Trusted Plumber GSR Top Contributor!!

    577 is great but won't work on anything plastic

    Sounds like you need loctite 55 or boss white and hemp
    • Like Like x 1
  3. Chalked

    Chalked Plumber GSR

    As Shaun says . Don't use 577 on plastic! It ONLY works with metal.
    • Like Like x 1
  4. Deuce

    Deuce New Member

    Thanks both of you.

    How reliable/foolproof is 577 generally? For example silicone smoothed into first few threads is normally extremely reliable, initially. But it's not reliable long term. So we need a high tech product that seals as reliably but also copes better with a little movement over time. Can't use a thread 'lock' product though as we do need to be able to break the connections sometimes..
  5. ShaunCorbs

    ShaunCorbs S. Mod Trusted Plumber GSR Top Contributor!!

    Never had a leak and you can disassemble when you need to
    • Like Like x 1
  6. Deuce

    Deuce New Member

    Have you used on threads up to 2"? And I assume just the 577, no other products used alongside it?
  7. ShaunCorbs

    ShaunCorbs S. Mod Trusted Plumber GSR Top Contributor!!

    Yep and straight medium non tapered pipe

    Even done an pita 4" one that was in a floor

    Follow the spec tho eg need to clean the cutting oil off before you apply it
    • Like Like x 1
  8. Last Plumber

    Last Plumber Plumber GSR Top Contributor!!

    I take it this is a threaded joint?
    What are you putting together?
  9. Deuce

    Deuce New Member

    That's very reassuring to hear! I'll get it ordered.

    Yes we clean the fittings, we use loctite spray cleaner.

    Thank you so much for the help ;)
  10. Best

    Best Trusted Plumber Top Contributor!!

    Don't use actual Boss White on anything plastic. It is oil based and will react with most plastics and destroy it
    • Like Like x 1
  11. Deuce

    Deuce New Member

    Yes, threaded fittings. Everything else we don in solvent weld as far as possible.

    The equipment itself is mostly pool filters/pumps. Which are normally all done with solvent weld. But we have to make the kit modular, mobile and very tough, so we often go onto stainless/brass fittings. We use composite bulkheads to go from one to the other unless we have no choice but to directly mate metal and plastic threads..
  12. Deuce

    Deuce New Member

    Thanks. As it happens I just ordered Loctite 5331 for the plastic threads. So should be all OK.
  13. ShaunCorbs

    ShaunCorbs S. Mod Trusted Plumber GSR Top Contributor!!

    Loctite 55 for metal to plastic threads
    Loctite 577 for metal to metal threads
    • Like Like x 1
  14. ShaunCorbs

    ShaunCorbs S. Mod Trusted Plumber GSR Top Contributor!!

    Never tried that myself let us know how you get on
    • Like Like x 1
    • Friendly Friendly x 1
  15. Last Plumber

    Last Plumber Plumber GSR Top Contributor!!

    I see. I was asking just to make sure that they are taper threads and not face joints.
    If you've sorted it, then all's well and good.
    • Like Like x 1