View Full Version : Galvanized Pipes on Hot Water Heating Systems

Nick Ostrowski
08-04-2007, 09:47 AM
I've been noting in my reports the presence of galvanized pipes on runs of hot water heating pipes for hydronic heating systems. I started wondering if galvanized pipes will have an affect on the performance of a hot water heating system in the same way they can affect water pressure over time in the potable water pipes. I know that the water contained in the hot water heating pipes becomes essentially chemically inert over time and may or may not cause the pipes to corrode from the inside out.

Any thoughts?

Nick Ostrowski
08-14-2007, 05:37 AM
Anyone? Bueller? Bueller?

neal lewis
08-14-2007, 06:53 AM

The oxygen in the water causes the rust buildup and reduces the water flow in water supply piping.

I have not heard of the same problems with hydronic heat. But, generally I see black iron for heating. I don't know about the inert quality of the water.

imported_John Smith
08-14-2007, 04:54 PM
Typically, you see calcium deposits choking off the pipes, and rust and pinholes developing under the calcium deposits. Anode+Cathode+Electrolyte = corrosion.

Corrosion is most aggressive on hot water piping as the temperature has a significant influence on corrosion rates. In a hot attic, with hot water - you are in the real sweet spot of corrosion development.

But - consider that the pipes are usually not the same temperature as the water in the heater because they lose heat when no hot water is flowing through them. In hot climates like Houston, most transplants from the North think they have a problem with their hot/cold water service as the cold typically puts out very hot water during our brutal summers.