stubborn leak on water line input to Kohler K-302 shower valve

[aeromike]

I'm having a heck of a time trying to get my hot and cold water connections on my Kohler shower valve to stop leaking. See photo below. I have not worked with this type of water connection before and I'm stumped on how to deal with this issue. It appears to be a ball and socket type interface that simply relies on the fit between the two surfaces and I cannot get the interface between the male ball and female socket shown below in the photo to stop leaking. The photo shows some residue from some plumbing thread lock sealant that I tried on the connection that did not work so I cleaned it up as best as I could.

Does anybody have any ideas on how to make a reliable connection with this type of water connection interface?
Thanks.

 

[Breplum]

That joint is called a union (maybe a 'ground joint' union).
They are typically easy and only thing needed is a drop of any lubricant of choice on the threads and a good wrench.
The metal to metal of the ground joint should hold. you could try some teflon tape for hoots and giggles. shouldn't be necessary and I would not trust it without permanent access.

 

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[aeromike]

Thank you so very much sir. I used some tri-flow lubricant that has teflon microparticles in it and the union nut snugged tightly and very smoothly with not even a hint of thread galling that you can sometimes feel through the handle of the wrench in the last few degrees of rotation before the nut is tight. The joint leak is gone. This is a very simple and elegant solution and I thank you so much for sharing your knowledge.