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Thread: Joining threaded PVC fittings?

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    Joining threaded PVC fittings?

    I have finally finished the new pipe work necessary to install a new filter pump (it only took me 3 months!) The inlet to the filter uses a threaded fitting though, so I'll need to use either teflon tape or a thread compound to seal the joint before I can try it out.

    PTFE tape seems to be a popular choice, however I've read warnings that the tape lubricates so well that it can lead to over-tightening of the threads, resulting in excessive stress (and possibly failure) of the fittings. Apparently the best choice would be a non-lubricating, non-hardening, PVC safe thread sealant.

    But Teflon tape is available everywhere, while thread compound with the above properties doesn't seem to be available locally.

    Am I worrying too much about this? Should I just go ahead and use tape? The threaded fitting on the filter valve seems to be glued in - if it did fail it would not be an easy fix!

    I'd appreciate any thoughts or advice anyone cares to share on the subject.

    Oh, a bonus question: I plan to use silicon grease on all of the union o-rings. Any reason not to?

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    Re: Joining threaded PVC fittings?

    Tape is fine. 3 to 5 thicknesses of the blue roll stuff, 3/4" wide is best. Threads MUST be clean.

    Scott
    Owner of - PoolGuyNJ LLC
    Expert Pool and Spa Repairs, Renovations, and Augmentation. Helping people decide what is the right gear for meeting their needs. Expectations Set, Expectations Met, No Surprises.

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    Re: Joining threaded PVC fittings?

    Quote Originally Posted by PoolGuyNJ
    Tape is fine. 3 to 5 thicknesses of the blue roll stuff, 3/4" wide is best. Threads MUST be clean.
    Thanks for that. Well, it sort of worked... There's a slow drip, so I'll need to redo the tape at some point. There was no sign of any leaks (either water or air) from any of the glued joints or unions though, so I'm pretty happy overall.

    I'm actually looking forward to vacuuming the pool tomorrow.

    I'm not sure what you meant by 'blue roll stuff' - white tape on a blue spool, or blue tape? The blue tape claims to be twice the strength of the standard white tape so I used that. Only 1/2" though, the hardware store didn't have anything wider. It would have been easier with a wider tape, I'll try and find some for the repair job.

    I redid the tape 3 times before I was happy with it, the first time I screwed on the fitting it ran out of thread without meeting much resistance, the second time I thought there was too much resistance too soon. The third time was just right, or so I thought...

    How tight should the joint be? (It's a 1.5 inch fitting if that matters.) I did it firmly hand tight, but could have tightened it a bit further by hand. I was more worried about splitting the fitting than a possible leak.

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    Re: Joining threaded PVC fittings?

    White tape, blue roll. Different thicknesses have different colored rolls.

    Scott
    Owner of - PoolGuyNJ LLC
    Expert Pool and Spa Repairs, Renovations, and Augmentation. Helping people decide what is the right gear for meeting their needs. Expectations Set, Expectations Met, No Surprises.

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    Re: Joining threaded PVC fittings?

    How big is that pipe? As a rule of thumb, I have always used pipe thread compound on anything over an inch.

    Others have used teflon tape very successfully on the larger sizes but it has always seemed a little finicky to me. I think if you do it pretty often, it is probably easy to get a good seal but a DIY guy (me) may have a little more trouble.

    As for the exact "qualities" of the compound, I have never used anything other than the basic stuff found in the plumbing department at Home Depot/Lowe's. I hope I'm not missing something and using the wrong stuff but I've had the joints threaded now for about 6-7 years with no problems.
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

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