For some reason, perhaps length, this part of my post refused to show in the Preview and in the post above. I had placed it in the middle of my original message just after the first question:
Here is the section that got my attention. I called my parts supplier and got a little more than incredulity. They just said, we always recommend Teflon tape.
" Don't use Teflon tape, Teflon paste or pipe dope. Do use a sealant.
Teflon tape, Teflon paste and pipe dope is intended for metal pipe and fittings. Metal to metal fitting joints are more difficult to tighten than plastic; the surfaces tend to gall without the aid of such lubricants as Teflon or pipe dope. Plastic fittings do not need this lubrication.
When Teflon tape is wrapped around plastic male threads it adds to the strain and tensile stress. The tendency of most installers is to incorrectly wrap several thickness of tape around the male threads, increasing stain and stress further.
Teflon paste and pipe dope, just like Teflon tape, make threaded joints slippery. Their use on PVC fittings can be an invitation to over-torque.
When working with threaded plastic fittings do use a proper sealant. The right sealant for threaded joints is non-hardening, compatible with plastic and doesn't add slipperiness.
A non-hardening compound is forced by water pressure into potential points of leakage, thereby performing a true sealing function. Tapes and hardening pastes permit a leak path to develop when a joint is backed off, mechanically flexed, or expands with rising temperatures.
A sealing compound must be compatible to plastics. Many brands of pipe sealant contain oils, solvents or carriers that can damage plastic. A proper sealant must be certified by the manufacturer to be harmless to the fitting material and to not contaminate fluid in the pipe.
Finally, a sealing compound must not lubricate the joint to the point that over-tightening is encouraged. Several sealants on the market meet all these requirements."
I found no recommendations. My voice mail to Lasco was returned and I was told to try two products, IPS AllSeal and Permatex® Soft Set Thread Sealant 61 Blue.
I did a bit more searching and learned that both of these products are oil based. About ten years ago I stopped using an oil based Teflon containing pipe dope on plastic because I thought it was weakening the plastic. I looked for the can, but I've misplaced it so I can't say what it was. The parts that failed were black plastic reduction tees that I used to install Pepco QuadraBubblers. Perhaps they were not PVC but ABS. Perhaps I just overtightened the joints because they were over-lubricated and easy to over-tighten.
There are more articles on threaded PVC. You can access them from the Lasco home page: