My garden hose pool filler contraption failed (again) and I'm trying to attach a less expensive float valve to the filler line. The pool filler PVC pipe is 1/2" and terminates flush with the pool wall. The 1/2" male threaded float valves have no way to attach to the pipe. I've tried turning down adapter fittings to fit inside the 1/2" feeder pipe and using marine epoxy to bond them together, but the water pressure blows them out. Is there a way to cut internal threads on PVC pipe? Another way to attach the float valve? Or am I stuck with replacing my Pool Sentry every 3 years?