Quote:
Originally Posted by rfuerst911sc
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From the folks who make them ...
whose recommendation matches up with my limited knowledge here.
https://www.bing.com/search?form=MOZSPG&pc=MOZI&q=threaded+PVC+joint
https://www.lascofittings.com/threads
The "Do's and Don'ts" of Assembling Threaded Plastic Fittings
Today, there are millions of miles of plastic piping with threaded fittings, providing reliable, leak-free service. However, a tiny percentage of those threaded plastic fittings may leak or break. The reason for this is improper assembly of threaded joints.
Here are some of the Do's and Don'ts of PVC joint assembly:
Don't over-tighten joints by giving them "one more turn to be sure."Do finger tighten plus one or two turns - No More.
Don't wrap Teflon tape or Teflon paste or pipe dope to add bulk to or to lubricate the joint. Do use a sealant for threaded joints.
Don't use "stronger" Schedule 80 threaded fittings on the assumption that they may solve the problem of splitting through over-tightening.
Do use only Schedule 40 threaded fittings with Schedule 40 pipe and fittings.
Don't over-tighten.
Do finger tighten plus one or two turns.
On threaded male PVC fittings each successive thread is slightly larger in diameter than the one before it. Female threads get successively smaller. This is called taper and the amount of taper is specified (1¾ degrees) in the American National Standard B2.1. All pipe manufacturers voluntarily follow these standards to assure their customers they are receiving quality materials.
Because the threads are tapered, additional turns cause the female part to stretch or undergo "strain." This will split the female fitting just as a wedge, driven by a sledgehammer, will split a tree stump.
The amount of strain increases as the size of the pipe decreases. Therefore it is easier to split smaller diameter threaded joints than larger ones. It is also easier to over-torque smaller diameter fittings because their resistance to torque is less. Table 1 gives Strain and Tensile Stress levels according to pipe diameter.
... lots of good plumbing tech stuff ... will read later !