I seriously doubt that the cast iron lines have anything to do
with your problem unless they are not set to adequate flow grade.
Cast iron can grow nodules on the inside of the pipe that snag
scum and solids, but I have never seen any grown shut to the point
of slowing water.

I suspect your problem lies elsewhere. If the original piping is
fairly easy and it would make you feel better, go ahead and
replace it. I just don't think it will be the end of your
troubles.

(top posted for your convenience)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Keep the whole world singing . . . .
DanG (remove the sevens)




wrote in message
ups.com...
Hi,

I recently posted about water backing into our tub on the first
floor
where the tub, kitchen sink and dishwasher all share a common
drain.
After having a plumber out to snake it it started happening
again today
so I snaked it myself and this time I was able to unclog it
myself. I
learned a couple of tricks watching that plumber!

But the big problem is that it keeps reclogging so we must only
be
opening a small passage each time we snake it. A guy I know
looked at
our plumbing downstairs and pointed to a section that is older
pipes
and said if I replace this one section it will cure the
problems. He
thinks the insides of that pipe have mineral scale built up and
that we
are only clearing a small hole each time we snake it. There is
a lot
of plastic pvc that was installed when we had our kitchen and
bath
renovated but there is this one section that is the old stuff.

What do the plumbing experts here think about this?

Thanks,
Steve