A few months ago we redid our water filtration system at work. We have an inlet and an outlet to a pump where it goes from PVC to a metal fitting into the pump, and from a metal fitting to PVC at the pump outlet. When we first assembled everything, those connections leaked. So we replaced them. We used a male PVC into a female threaded metal fitting with teflon tape. Everything was great for about a month. Today they both started leaking again. What would cause them to begin leaking after being fine for a month or so, and what do y'all think is the best way to fix the problem so I don't have to go fix it again next month?



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In my humble opinion, I suggest eliminating the use of plastic threading altogether. Sharkbite connections can provide a metal to metal thread, and would have the fewest joints. If you were to go as far as putting on something like this, you could eliminate the transfer of vibration between the pump to the rest of the system.

If the pump is running against a "dead head" without a flow, it will cavitate and heat up and that can cause male PVC threads to loosen and start leaking.