Not much debate - a non hardening thread sealant designed for PVC pipe is the preferred method and recommended by manufacturers. I've used both, and IME the thread sealant works better and is easier to use.
Is this the stuff to use?
Oatey 31230 Pipe Joint Compound with PTFE with Brush, 4 fl.Ounce
Description:
Non-hardening gray paste seals and lubricates threaded joints
For use on water, steam or air lines
Non-separating and non-toxic material
Not for use on Plastic threads
Lubricates and seals all threaded joints.
White, non-hardening, non-separating, non-toxic paste.
Withstands up to 3,000 PSI on gases from -50° to +400°F, and 10,000 PSI on liquids from -50° to +500°F.
For use with water, steam, caustics or dilute acid lines of PVC, CPVC, ABS, cycolac, polypropylene, iron, steel or copper
http://www.amazon.com/Oatey-31230-J...dening+joint+compound+thread+sealant+PVC+pipe