Brass and stainless compatibility

kcopp

I just read on another website that brass and stainless threaded fitting/ nipples do not play well together in potable water.... is this true? If so Why?

Alan (California Radiant) Forbes

It depends on what kind of stainless steel. Copper is in the middle of the galvanic chart:

http://www.npfasteners.com/pdfs/galvanic-corrosion-chart.pdf

The further away you get from copper on the chart, the more likely you will get a reaction.

SWEI

The series also changes with different electrolytes. Many of the standard tables are based on low oxygen seawater.

kcopp

the fittings I am looking at are 304.
So many water heaters are 316.
We commonly use copper & brass fittings to hook these up.
Makes me wonder now.
Brass may be a better alternative.

SWEI

We've been using 304 SS nipples for about two years now -- remediating non-barrier piped RFH systems, for unpressurized solar drainback, and on DHW.

ISTR the inner tank on the SMART series are made out of 304 (or 304L) and those work fine with our city water. I will monitor the DHW installs (especially the ones that are running continuous 140-160°F temps) over the next few years just in case.

If the chloride levels in the water are such that they cause issues with SS indirects, I would certainly consider 316 instead.

Paul48

Some of the lower grades of stainless will actually hold a magnet, and rust in the right(or wrong) conditions.