I bought a Fluidmaster bottom entry float valve to replace an old ball valve in a toilet. While I was trying to tighten it onto the pipe connection I didn't notice a fibre washer had deteriorated and was bulging on one side, and as I tightened the connection it pushed the valve thread out of alignment and caused me to slightly strip the plastic thread. I managed to correctly rescrew everything after replacing the washer, but now I can't get the connection tight enought to stop it leaking. I've tried PTFE tape and Bosswhite, but it seems to need so much force to tighten the nut to stop leaks that the other end of the valve connection keeps unscrewing (where it enters the cistern). I can't find anyway to get both ends of the valve to screw in without leaking (to the cistern and to the water feed). I've probably ruined the valve thread and should buy a new one, but is there any way to fix it?
Thanks,
Ken