Slow draining sink - rusted galvanized plumbing
I had two slow draining bathroom sinks, one of which cleared up beautifully when I replaced the trap (clogged with rust and other gunk). I tried the same fix on the other, but it didn't help much, if any. So I took the trap back off and ran a hand snake through the galvanized pipe that goes into the wall (this was rusted pretty bad, but not any worse than the other sink). The snake would only go in about 2 ft before it got completely stuck. I'm guessing the rust is built up much worse somewhere in there, causing the blockage. I will probably rent an electric snake and give it another shot. Other than that, are there any tricks to this type of situation?
I suppose the worst case scenario is that I will need to replace the galvanized plumbing. I was told that the house sits on a slab foundation and that the plumbing is likely encased in the foundation. Any idea of what this type of job would cost? I know you would have to see it first, but any kind of estimate in thousands of dollars would help me get a feel for what I'm dealing with.