Is mixed plumbing a red flag?

Question

Somewhat odd question. I have a single family rental, which had updated plumbing about 20yrs ago, mostly copper, but the silly do it yourselfers have several occasions where that copper is touching steel duct work and other steel. If you know anything about metals, they don't love resting against other incompatible metals. I'm not a scientist (or a plumber), but I believe it's the steel that is corroding, not the copper. So maybe I can just put some plastic between them and call it a day, but my fear is that in the future the copper could leak, which could result in thousands of dollars in damage depending on when it's finally noticed. So my thought was to just replace that entire section with PEX.

So here are my two questions:

- Is it the steel, which is corroding? If so, I think I'm okay.

- If you were looking at buying a house or investment, and you saw a random area of PEX, would it make you worry that the house is filled with plumbing issues and that what you see is just one visible problem amongst many problems hidden behind the walls?

That second question is my concern with this plan. I suppose another option is to sweat new copper and protect it from steel this time, but not sure that really addresses my concerns.

Thanks in advance!

Scott E. · Answer

Nearly every house I've bought has had a mix of plumbing materials (most of the homes I buy are build in the 1950s).

I don't worry about random areas of copper or PEX. Both are fine ways to route water around the house. And running new lines is relatively affordable in the event you need to swap anything out.

Your steel on copper concern on the other hand does need to be addressed. I'd speak with a plumber on that one though.

David Lee Hall, III · Answer

I have had to fix this as well a couple times. Once when an HVAC guy almost electrocuted himself! The other time is a house I am currently working on and the ground was tied in at the outside faucet. When I replaced that with frost free and the plumbing to it with PEX, I had to reroute the ground back to the other side of the basement to tie in to the main shutoff which was still copper. This was also an instance of paying a contractor to go away. Electrician was upgrading my panel and was supposed to do this as part of the upgrade but stole a bunch of my supplies instead. Grrrr.

George Kopp · Answer

Thanks everyone. This makes me feel better about doing the right thing for the longevity of the house. I'm a big believer in overengineering vs. having an emergency call I have to deal with or pay top dollar for. I just needed some reassurance that a potential buyer down the road wasn't going to look at that random stretch of PEX and wonder if there was a fail, which could signify trouble behind the walls.

And while I also have done a mix in the past in cases where let's say a home is plumbed in copper but we are gutting the bathroom, so I'll do the entire new section in PEX (Uponor is my go to), and I know no one would ever bulk at someone updating a new bathroom with what is considered the modern alternative to copper. I was just worried that a random section in the middle of the basement of copper to PEX back to copper, or maybe to the water heater, would raise some eyebrows.

But given the comments, I think I'm going to do it. That copper has been touching the galvanized for 20yrs. I'm really nervous about the integrity of that section and don't need a call from my tenant saying the entire basement is flooded.

Cheers!

Jim K. · Answer

This is not a red flag. Now, if you have galvanized steel water supply plumbing that you want to leave in place running into newer copper piping, and you probably don't, you'll need a dielectric or brass union between the two. But where copper water supply piping just runs alongside or touches steel? It's not going to be a problem, ever.The only thing to be careful about when you find random PEX fixes in an older houses, usually in an exposed basement, is the chance that someone grounded power outlets to copper or steel water supply lines up on another floor in some random remodel way back when and these outlets lost all  grounding when the PEX went in. You tend to see that sort of thing when big old houses get converted into duplexes by people of questionable ability and maintained by those with even less.

Is mixed plumbing a red flag?

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