Plumbing PEX compatible ground union?

Stephen Tashi

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Summary
Is there a ground union fitting that can be installed directly to PEX pipe?
Is there a "ground union" type of fitting that can be installed in PEX lines without requiring additional adapters that screw into the fitting?

I need to plumb a whole house sediment filter. Ideally, I like a union fitting that was PEX on one end and threaded on the other. This would allow me to re-do the connection to the filter housing if the first test showed it leaked. It would also allow easier replacment of the filter housing if that is ever needed.
 

berkeman

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Sorry, I'm no expert on plumbing, but why would you need to ground PEX "pipe"? It's non-conductive, no? The fittings appear to be metal, but if the PEX pipe is non-conductive, it doesn't seem like grounding would do anything. Or are you using the term "ground union" for something other than electrical grounding?

 

Stephen Tashi

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I'm using the terminology "ground union" because, on the web, I read that it's a particular type of union fitting. The adjective "ground" doesn't refer to an electrical ground. I'd actually be interested in any type of union fitting that was easy to install in a PEX line.
 

chemisttree

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Stephen Tashi

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Use “adapter” in your search term rather than “fitting”. Totally different results!
The problem is that "adapters" are not unions. A union is a fitting that can be unscrewed to allow easy replacement of whatever device ( valve, regulator etc) the union attaches.
 

berkeman

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Maybe two adapters in series then? :smile:
 

chemisttree

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Your union goes on the appliance and would screw into the PEX adapter, then?
 

Stephen Tashi

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Your union goes on the appliance and would screw into the PEX adapter, then?
It can be done that way. What I'd prefer is a union that had one side already adapted to PEX. An adapter wouldn't be needed. There would be one less joint to worry about.

In my recent plumbing experiences, brass-to-brass threaded connections are the most difficult to get leak free - even with teflon tape or thread sealant. If I attach a brass bodied pressure regulator in the middle of a PEX line using adapters on either end, then to tighten or re-do a leaking joint between the regulator and an adapter, I must first release the adapter from the PEX line by cutting the clamp that holds the PEX line and perhaps use a heat gun to get the PEX off the adapter.
 

chemisttree

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Perhaps behind-the-wall installations for regulators and temperature mixing valves are done with no thought of how to quickly replace them because of what you have experienced with leakage. But I can’t imagine a ground union would fare much better in that application but they do make quick connect PEX adapters. Sharkbite sells them.

 

chemisttree

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Page 13 of Sharkbite’s catalog has a water filter installation kit. Should be something there for your application.
 

Stephen Tashi

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On this project ( entry of main water line, shut-off valves, pressure regulator, sediment filter) I plan to install everything in plain sight - nothing inside walls! I've used Sharkbite press-on fittings in a temporary role, but don't trust them long term.

As a digression: My experience with Sharkbite press-ons is they don't leak when applied to pipes that are new and round. On old copper pipe that is out-of-round, they may leak. They are not recommended for copper "tubing" - the copper sold in rolls - as opposed to copper "pipe" which is sold in straight lengths. The press-on fittings are not as easy to remove as is often portrayed on the internet. I bought special pliers-like tool to take them off.
 

Averagesupernova

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My opinion on plumbing fittings is to avoid anything that is uncommon. I try to find a way to make the connections using quite readily attainable fittings. If for some reason down the road I need to do a disassembly and ruin a fitting in doing so, it will be easier to find replacements. My 2¢.
 

marcusl

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At one time, the mating parts in a ground union were ground together with a polishing compound to get a leak-tight metal-to-metal seal. This is still done to valve/valve seats in high performance automotive engines. These days I think unions are just machined with a flare to achieve a seal, but the name endures.
 
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These are readily available in the UK for a number of plastic pipe solutions e.g. https://media.screwfix.com/is/image//ae235?src=ae235/5653F_P (Hep2o is a PB system which I do not believe is permitted in the US) but you would need to find one suitable for your US supplied pipe.

If there is not a specific fitting available then use a compression adaptor to join the PEX pipe, using the correct insert (I assume this is allowed/available in the US?)
 

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