Dissimilar metals should not be joined, but it’s okay to join a brass manifold to steel pipe? Should I hunt for a steel manifold?

There are a lot of mixed messages about plumbing with dissimilar metals. Mainstream local plumbing shops sell brass manifolds. They say I can connect the brass manifold to steel pipe. Copper is very dissimilar to steel, and fittings for copper are brass. So if it’s okay to connect brass to copper and brass to steel, why couldn’t a copper pipe be connected to a (steel) hot water tank simply using a brass fitting? It’s supposed to be a dielectric fitting that insulates using rubber so the metals don’t touch.

OTOH, there is a gas-fired tankless boiler with internal copper pipe and a professional directly attached those copper pipes to galvanized steel pipes. Youtubers say copper should never join steel and they show examples of corrosion.

The question at the moment is whether this is a good idea:

galvanized steel pipe → brass manifold → galvanized steel pipe

I can get brass that is nickel plated externally, or it can be simple brass. The nickel-plated manifolds have integrated PEX valves. If one valve goes bad, then the whole manifold needs to be replaced as a single piece.

Shouldn’t the manifold also be made of galvanized steel? I wonder if it’s worth it to go on a hunt for something that’s uncommon.

#askFedi