PEX to Water Heater connection

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Brett Sanders

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Hi,

DIYer here replacing galvanized piping throughout home with PEX. When connecting the PEX to the water heater lines (in and out) can I just use a threaded PEX fitting into the dielectric unions that are there from the galvanized to copper connection? There is already over 18 inches of copper connected directly to the water heater so no issues there, it's just connecting the PEX to the copper. I attached a picture of the connections it is right now. It's 1 inch PEX that is going to be a short run to a tee branch off to 3/4 and a small 3 port manifold.

20211229_213737.jpg
 

wwhitney

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I think the OP's question was "it was easy to terminate the new PEX to a fitting that attaches to the existing dielectric union, is leaving the dielectric union there a problem?" I presume because the dielectric union is soldered on one end, and dealing with that solder connection would be additional trouble for the OP.

Cheers, Wayne
 

Terry

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Or if the PEX fitting is a 3/4" male fitting, the corrugated supply would thread on nicely.
He mentions 1" PEX, but the fitting looks to be 3/4"

corrugated-wh-supply-01.jpg


 
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wwhitney

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Or since the PEX fitting is a 3/4" male fitting, the corrugated supply would thread on nicely.
I don't see any corrugated in the picture, I think the "over 18 inches of copper connected directly to the water heater" is all hard pipe.

Cheers, Wayne
 

wwhitney

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Still not clear on the answer to the OP's question: the OP got rid of all the galvanized pipe because it rusts. Will the isolated dielectric union rust on the silver side? Or will leaving it in place be fine?

I'm not familiar with the construction of dielectric unions, if the silver side is all plastic lined so that there's no wetted ferrous metal, I would expect it to be fine to leave in place.

Cheers, Wayne
 

Terry

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What do you use in place of a dielectric union?

The 24" corrugated does the same thing. I'm in earthquake country, and they want flex connections here.
Also, they prefer a 6" brass nipple over the union pictured above, which will fail very quickly. We consider them a waste to install.

I almost never install an 18", the 24" allows for a much nicer bend.
 

John Gayewski

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The 24" corrugated does the same thing. I'm in earthquake country, and they want flex connections here.
Also, they prefer a 6" brass nipple over the union pictured above, which will fail very quickly. We consider them a waste to install.

I almost never install an 18", the 24" allows for a much nicer bend.
I'm almost too the point where I'm sold on thr flex connectors. What's a good full sized option?
 

Terry

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I'm almost too the point where I'm sold on thr flex connectors. What's a good full sized option?

I keep both 18" and 24" with me. I mostly just pull out the 24's, much easier to install.
And they last as long as the water heater in my experience.
New water heater, new flex.
Remove a flex at any point, toss it and install a new one.

corrugated-wh-supply-01.jpg
 
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Tuttles Revenge

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I wouldn't leave that old dialetric union for the same reason as Terry shows. They will rust.

How was the electrical bond taken care of?
 

Brett Sanders

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I don't see any corrugated in the picture, I think the "over 18 inches of copper connected directly to the water heater" is all hard pipe.

Cheers, Wayne
Yeah it's over 18 inches of hard copper that is brand new because I needed a new water heater and needed it before I started my PEX project so the plumber just connected to the old galvy stuff. If reusing that union works I'll go with that.
 

Brett Sanders

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One of my issues is I can't get the union at the heater itself undone, probably lack of correct tools, otherwise I would connect a corrugated pipe or something directly to the heater and connect the PEX to that. See pic of whole setup.

20211230_125015.jpg
 
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