When threading together PVC plastic pipe joints on a sprinkler valve repair you may wonder which should I use on the threads, teflon tape or teflon paste?
The answer is a little of both is best. It is best to apply a small thin layer of Teflon paste on the male pipe thread then wrap teflon tape tightly about 2 to 3 complete wraps around the fitting. Be sure it is teflon and not pipe dope. Pipe dope contains petroleum and will actually dissolve or melt away at the plastic possibly causing catastrophic failure. Careful to never over tighten plastic pipe joints together. This can cause the female side to crack. Another helpful trick is to lubricate with water the threaded joints before you screw them together this avoids the teflon tape and paste from getting scraped away from the threads. One more valuable hint is to beval the male pipe thread. This will enable the male fitting to screw further into the joint without it being over tightened. Remember to brush away any little plastic shavings from the thread’s before using the paste and teflon.