PEX compatible ground union?

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  • Thread starter Stephen Tashi
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    Ground Union
  • #1

Stephen Tashi

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TL;DR 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.

Answers and Replies

  • #2
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?
  • #3
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.
  • #4

Use “adapter” in your search term rather than “fitting”. Totally different results!
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  • #5
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.
  • #6
Maybe two adapters in series then? :smile:
  • #7
Your union goes on the appliance and would screw into the PEX adapter, then?
  • #8
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.
  • #9
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.
  • #10
Page 13 of Sharkbite’s catalog has a water filter installation kit. Should be something there for your application.
  • #11
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.
  • #12
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¢.
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  • #13
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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  • #14
These are readily available in the UK for a number of plastic pipe solutions e.g. (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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