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Thread: Pipe thread

  1. #1
    Join Date
    Nov 2003
    Posts
    23
    IM looking for some help I need to seal pipe threads what is the best pipe dope to use I have a brass 1" valve and a 1" schedule 40 pvc adapter with male threads going in to the brass valve Water is going in to a heat pump units water temp 75 to 90 degrees teflon tape and teflon dope doesn't seem to be working. any help will be appreciate Thank you Herman.

  2. #2
    try another pvc adapter you may have screwed up the threads.Teflon tape and laco blue soft seal, liberally. when tightening make sure yuo use the right size wrenches and you should see a bead of the blue sealant build up as you tighten the fittings. Also make sure you wrap the tape in the propper direction.
    hope that helps

  3. #3
    Join Date
    Jul 2004
    Location
    Red Lion, PA
    Posts
    62

    Smile

    Do not use teflon or dope! use a good quality rtv silicone we have had problems in the past with our guys and teflon if you put to much on you can crack or distort the fitting causing a leak. the same for dope it makes the threads seat deeper than normal and can crack the female piece if its say a condensate pan .Ive found that a ring of rtv about a 1/4 way in on the male thread works great and have never had a problem

  4. #4
    Join Date
    Dec 2003
    Location
    Nevada
    Posts
    1,815
    rectorseal
    Quote
    “Engineers like to solve problems. If there are no problems handily available, they will create their own." Scott Adams

    "We can't solve problems by using the same kind of thinking we used when we created them."
    Albert Einstein

  5. #5
    Join Date
    Mar 2003
    Location
    NY
    Posts
    2,164
    I wouldn't mix brass and pvc threaded fittings on a heat pump loop. These joints will leak until the building is bulldozed.
    The cheapest solution is to use pvc valves and threaded fittings after. That way you can close the valve and fix the leaks for years to come. The other option, and in my opinion the best, is to flange the fittings. Pvc flange to threaded flange.

    Just to clarify, if you dont think the loop temp will ever go above 90f....... The differential in expansion rate will always cause the thread to leaks.

  6. #6
    Originally posted by dapper
    I wouldn't mix brass and pvc threaded fittings on a heat pump loop. These joints will leak until the building is bulldozed.
    The cheapest solution is to use pvc valves and threaded fittings after. That way you can close the valve and fix the leaks for years to come. The other option, and in my opinion the best, is to flange the fittings. Pvc flange to threaded flange.

    Just to clarify, if you dont think the loop temp will ever go above 90f....... The differential in expansion rate will always cause the thread to leaks.
    Your standard PVC dont do heat well. That is why CPVC was developed in the first place.

    In industrial sites, that gray PVC is used. It is much more expensive, but it works well and is very sturdy.

    Flanges work well. Teflon rope or Teflon string is good for flanged joints.

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