Brass union vs Copper union

[PrecisionPlum]

Anyone have thoughts on Brass vs Copper unions.

Is one better over the other?

Your experience with them.

Thank you.

 

[Mitchell-DIY-Guy]

If I'm not mistaken, a copper union would probably be one that has sweat fittings for soldering. A brass union would be threaded.

The reason for this is brass, being a copper alloy, is a bit harder than pure copper, about twice as hard on the Brinell scale. Thus it can take threads a lot more robustly than copper.

So, if you want to re-use the fitting or are working with threaded pipe, etc. brass may be called for. If minimizing your work, use a copper sweat union.

 

[PrecisionPlum]

Any thoughts about one having greater reliability in providing a dependable seal then the other?

 

[Mitchell-DIY-Guy]

When I use any kind of flare fitting or a union, on the mating surfaces I always put a small wipe of thread sealant. That would be regardless of copper or brass, (or iron or stainless steel, just not on plastics).

My thread sealant of choice is: https://www.henkel-adhesives.com/us/en/product/thread-sealants/loctite_567.html

A well experienced plumber taught me to use this on mating surfaces as well as on threads WITH teflon tape. Never have I had a leak or issues.

Once properly assembled, regardless of copper or brass, I think you'll be fine. So why use one versus the other? There's the time and cost with threaded vs. unthreaded. Brass unions are probably twice the cost of copper, and if you are putting them on conventional copper pipe/tube, then you have additional fittings to get threads; threaded adapters. But as for the robustness of the union itself probably doesn't matter much in most environments.