Is there some advantage to having a bronze pump over cast iron?  I currently have an Armstrong E9B (bronze) that i am investigating replacements for for the day i need to replace it.
Thanks

bronze pumps found in residential application are designed primarily for use in potable water systems. There is no advantage when used in a proper closed hydronic system.

Bronze pumps are required when there is no oxygen barrier in the piping, PEX however has the oxygen barrier so there is no need to spend the extra money for Bronze.

PEX (cross-linked polyethylene) may or may not have an oxygen barrier.

Ferrous (Iron) VS non Ferrous (Bronze)
If your system is a non ferrous or all non Iron/steel system you will likely want to stay with a bronze pump.
If you have an iron boiler, steel pipes and or parts, steel or cast iron radiators and so on the bronze pump is not doing anything for your system.
With a non Ferrous system oxygen barrier pipe is unnecessary.
Dan

What is the function of the pump?? Hydronic heating, Solar DHW, DHW circulator, ??
What type of fluid is it pumping?? Potable water, nonpotable water, glycol mixtures, silicon or mineral oils??
What materials make up the rest of the system? Pex, copper, galvanized pipe, etc ??
I would assume that the original installer had a reason for the bronze pump and would only change it to cast if I were POSITIVE that it was compatible with the intended use.

Bronze in a non oxygen barrier situation... OK. I have non oxygen barrier PEX installed in a slab. Therefore I have to use a bronze pump? Why? What happens if another one is used?

And no I have not installed anything yet. The pipe was put in for future use. At present shop is not heated. I'm just slowly collecting info for when it is needed.