Teflon tape isn't a good idea on PVC threaded fittings, according to the fitting manufacturers. The primary purpose of teflon tape is to lubricate the treads so the fitting can tighten further with less effort, and that leads to breaking the PVC female fittings. Instead, the use of thread joint compound, a paste, which is made for use on PVC pipe, is recommended. Then notice that most PVC pipe thread connections don't have wrench flats or they have minimal wrench flats. That means they are not intended to be tightened with crescent wrenches, for example. Instead, tighten them by hand, plus a little with a wrench or adjustable pliers (not recommended by the manufacturers, but it works.) You have to get a feel for what the right torque is, judging by what you have found makes a non-leaking connection. It doesn't take long to learn what too much torque is, but the fittings are cheap, so replacing the broken ones isn't that big a deal.