Galvanized steel supply pipes

Is there any non-invasive way of identifying the existence of galvanized steel pipe in plumbing system (other than the tell-tale rust colored water) when the pipes are buried in finished walls or floors? I had read somewhere that a process existed which allowed a properly equipped person to measure the electrical conductivity of the pipe to determine if steel pipe exists along the run (steel and copper conduct differently).

A house that I inspected yesterday had a long-unused second floor bathroom and a tub in a separate room that delivered rust colored water (hot side only) when first turned on and for a couple minutes thereafter. (classic sign of steel pipe). However, the visible supply pipes throughout the house, including the unfinished basement were all copper.

The regularly used faucets didn’t show any color that was visible to the eye. There was no visible staining inside the 10+ year old dishwasher on the main floor of the house.

Note that the water heater is old (23 years) so rust in the heater tank is another possibility.

Yes there is, and you addressed it.


Visible supply pipe is copper.

Leave it right there and stop over thinking.

You should have a water pressure comment section in your report also but never play on something unless sure.
I may have asked the present owner and left it at that.

Not yelling ,just suggesting. :slight_smile:

Easily accessible old piping are usually replaced while less accessible piping are left in place (e.g. vertical piping between flooring).

While in basement/crawlspace look up for piping going to the upper flooring and you may be find galvanized supply and cast iron drain piping…

Food for thoughts,