Stacks (galv or cast)

How can you tell the difference between Galv steel stacks and Cast Iron. Do the Cast iron pipes rust a lot more? Both Magnetic and appear too similar to me.
Any help would be appreciated.

Galv steel waste lines are a concern, with known corrosion issues. They will be duller grey in color for older pipes. Joints are generally threaded, but can be no-hub for repair. Galv steel was used for old smaller fixture and branch lines.

Cast iron waste lines are more durable, and will be a black or dark in color. Joints are generally bell-and-spigot for older pipe or no-hub for newer pipe or repairs. Larger 3" waste stacks will almost always be cast iron instead of galv steel.

Note that sometimes exposed metal waste pipes are painted, and there are other types of branch and stack pipes, but they are hard to confuse for galv steel or cast iron.

Hope that helps … :wink:

DWV - CI Hubless Joint.jpg

DWV - Cast Iron Pipe.jpg

DWV - Galvanized Steel & CI.jpg