Proper way to join PVC pipes to brass ball valve
This is the standard method of attaching PVC pipe to threaded fittings. More turns and less tape. Pipe threads are tapered, in my experience 1-2 turns past hand tight is not nearly enough (and I generally only use 3 turns of Teflon tape).

Make sure that your brass ball valve is not cracked, brass is fairly soft and I have seen the threaded part of brass valves crack longitudinally due to over-tightening, especially with some of the cheap thin imported crap valves these days.

If you want to be able to unscrew it later without cutting the pipes, install a union.