I went to prepare for a water heater drain and anode replacement and noticed something troubling. The water heater side of the cold water valves is corroding.

House is a 2017 build. As far as I can tell everything behind drywall is PEX.

Ball Valve
WH Connector

Do I just need to clean things up and buy a new(higher quality?) fitting for in between them? Is this a case of the wrong materials touching and I should somehow reorder or choose different fittings?

I'm guessing this 3/4 in. MIP Lead-Free Brass Pipe Hex Nipple Fitting would be the direct replacement of what is corroding but will it just happen again? Or is it the valve?

Album with pictures

Usually it was a tiny leak that made the corrosion from mineral buildup. Wouldn't worry about it much.

Be prepared that getting the old anode out will be a MAJOR pia. Buy a long pipe to use as a breaker bar. Break it loose before draining. Ask me how I know.

If going to the trouble upgrade to the better type of metal for the anode. Mg? 3 years isn't enough time for the original to be bad yet.

From the pics it looks like they mixed galvanized nipples with a brass shut off. Galvanic corrosion may occur if dissimilar metals are connected together in a plumbing system. Go back with brass nipples and a brass shut off and you should be fine

I agree with Absolute that it appears you had a tiny leak at that connection point that caused the corrosion from mineral buildup as it's only evident on that one side of the threaded fitting.

If it was a dissimilar metal issue, you would see the same on the other threaded fitting.

Edited as JP76 opened my eyes and I corrected my stance in my follow-up response below!

The other fitting by the pex looks to be a brass fitting instead of galvanized like on the heater side

JP76 said:

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From the pics it looks like they mixed galvanized nipples with a brass shut off. Galvanic corrosion may occur if dissimilar metals are connected together in a plumbing system. Go back with brass nipples and a brass shut off and you should be fine

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This was my hunch too since the corrosion is nearly identical for both water heaters.

Its a cheap troubleshooting step either way. If this is the problem, anyone know if the brass valve can be brushed clean and kept in use? In other words, would it be the brass or the galvanized nipple that is degrading?

JP76 said:

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The other fitting by the pex looks to be a brass fitting instead of galvanized like on the heater side

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Ah, Yes, you are absolutely correct JP76. I didn't catch that.

Yes, the galvanized fittings need to be replaced with brass fittings, Timber08, in order to prevent the galvanic action that is taking place and causing the corrosion!

Awesome, thanks for the help. Without the ability to run to the hardware store multiple times I wanted to get some advice before I make an online order.