The kitchen drain uses 2" galvanized piping that's fifty years old. It
clogs up sometimes and I have to use the power auger drill attachment
to get things moving again. There is the potential that the drain
could decide to clog when the dishwasher is draining and nobody is
around to prevent the flooding.

So, looking into replacing a section of galvanized pipe with PVC. It's
all exposed in the basement so access is not a problem. What I noticed
is that the pitch of the five feet of horizontal portion, before it
reaches the 45 deg elbow going to the main waste line, is slightly in
the wrong direction! So what I think is happening is the solids are
settling back near the 90 deg sweap instead of heading downstream, thus
choking of the sweep connecting the vertical portion coming from the
sink to the horizontal section.

My fear is that the horizontal run is probably pitched wrong because it
is supporting the weight of the galvanized vent stack that tees off of
where the p-trap enters the line upstairs. Cutting out the horizontal
portion of the galvanized pipe could then create more problems if
everything shifted. I don't want to try too hard to jack up the
horizontal pipe given its age, but if I could just a bit what could I
use to suspend the galvanized from the floor joist above it? This
stuff is pretty heavy.

Thanks!