Why mixing copper and galvanized pipes is a bad idea in your home.
If you are the proud owner of an older home in one of the more vintage neighborhoods in South Africa, you are probably aware of the old galvanized or “Steel” Plumbing pipes in your home. No doubt you have had more than a few plumbers around to fix leaks here and there. There is a common problem these days with fixing these pipes.
In most cases a plumber will not replace the pipes with steel galvanized pipe (It takes too long and requires specialized pipe threading tools) but rather adapt to copper, this results in a “temporary” fix, but long term it accelerates the corrosion of the existing pipe work in your home. This accelerated corrosion of pipes is called galvanitic corrosion.
Galvanized pipes should not be connected directly to copper pipes, period. The only time one can successfully replace a section of galvanized pipe with a section of copper is to make use of a dielectric union to ensure the metals do not have direct contact. In layman’s terms, this can be a simple brass fitting that separates the 2 metals (Being copper and galvanized steel). Brass is an alloy of copper and nickel. It provides a nice transition between piping of copper and galvanized steel (which is coated with nickel). The brass transition prevents an immediate potential difference between copper and galvanized steel, hence preventing corrosion in the long run.
So in short: when you are planning a major renovation of an older home with galvanized pipes, you need to make sure that your plumber installs new copper piping, or at each connection with the old galvanized steel, your plumber must Separate the 2 metals with a brass fitting, or a specific dielectric union that has a plastic lining separating the 2 metals.