Water heater leaking

It takes time for electrolysis, even months or years. I am assuming this is right after he replaced the fittings? PEX pipe is plastic and I don't think you can get current flow through plastic.

A couple wraps of Teflon tape should be plenty on any fitting. Wrap so when you turn the fitting in it does not un-wrap.

Wondering how old the WH is and did this just start?

Not a plumber but I know how to pipe water, gas and refrigeration lines among other skills.

DennisG9 wrote:
Had black plastic 1/2 in pipe fittings for inlet and outlet pipes going to Plex lines. They started weaping at tank connection. Replaced them with copper theaded lines. Now they are leaking. I used teflon tape to seal the treads. Need something that works with the difference in expansion rates between aluminm tank and hard lines.

Any ideas??

I believe what is happening is electrolisys of copper being in direct contact with aluminum.

I replaced a plastic check valve (that cracked) with a brass one on my water heater with no leaks. How much Teflon tape did you use. You need about 7 wraps to make it leak free.

Have you tried this....re-establishing an air pocket at the top of the tank to allow for expansion?

To replace the air start by turning off the water
heater system, shut off the incoming water supply
and open the closest hot water faucet. Pull the
handle on the pressure-temperature relief valve
straight out to allow the water to flow from the top
part of the tank. Once the water has stopped
flowing allow the handle on the valve to snap shut,
close the faucet and re-engage the water supply.

They are both leaking? How old a tank, did they leak from day one? I have replaced plastic PEX fittings with copper or brass fittings without an issue. How do you crimp the PEX rings? Hose clamps usually will not seal tight enough.