How best to change a section of PEX hot water return line between two FIP tee fittings?

Question

I want to change the section of PEX hot water return line between the 1/2" tee fitting near the floor beam and the 3/4" tee fitting at the water heater drain.

I want to keep it simple with the fewest fittings and joints. However, I want to add a ball valve at the 3/4" tee so I can isolate that section of line without draining the tank. I want to stick with PEX line, but I was thinking of using shark bite type fittings.

I have zero plumbing experience and not a lot of common sense. I had a licensed plumber plumb my house, and the return line in the pic is his handy work.

I had to remove the water heater so that I could have a concrete floor installed. I ran into a problem when I went to reinstall that section of return line. As I was tightening the ball valve onto the nipple it was loosening up from the PEX fitting. I had a similar problem connecting to the nipple at the 3/4" tee.

I have slow leaks on both ends.

I've done some research and scoured Home Depot dot com. It seems like this should be as easy as connecting a garden hose to two faucets.

Answer 1

You don't need to replace anything.

Hold the Tee/Valve so they don't move, tighten the PEX fitting to each one, done. If the other end is also leaking, start with tightening them into the other fitting, finish with tightening the PEX fitting.

Standard PEX threaded fittings rotate so they act as unions (you turn the fitting, not the tubing, it spins inside the tubing)

You probably need some pipe dope, since you have "zero plumbing experience" and are working with threaded fittings. In that case, remove the fittings, apply dope to the outside of the male threaded part, reassemble. But you can start with trying to just tighten things properly, as there might be enough left on the fittings from before.