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Posted by hallerb@aol.com on July 26, 2007, 11:11 pm
> Eigenvector wrote:
> >> On Wed, 25 Jul 2007 21:46:48 -0700, "Eigenvector"
>
> >>> Do cast iron pipes rust inside to any large extent? I'm looking at
> >>> replacing the galvanize waste pipes that go to my septic and they meet up
> >>> at
> >>> the main line and dump into a cast iron pipe. The galvanized is rusted,
> >>> no
> >>> question, but I wonder if the cast iron would be too? I really don't want
> >>> to replace the sewer line into the septic tank.
> >> Cast iron will rust but then the rust on cast iron forms a sort of
> >> protective coating, preventing total rust through.
>
> >> However, what really happens with cast iron piping is that stuff
> >> adhers to the internal rust layer, especially chemical deposits. The
> >> pipes will slowly close up to the point of clogging.
> >> Regularly snaking out drain pipes will reduce this effect.
> >> I've used power snakes with cutting blades. Even they sometimes have a
> >> hard time cutting through the hardened crud. Let the pipe almost close
> >> down and it can be impossible to snake out.
>
> >> Doug
>
> > Doesn't sound like it reacts like galvanized then. whereas in galvanized if
> > you have rust, that means the walls of the pipe are seriously thin and at
> > the point of failure - reaming them out won't help, it will only hasten the
> > failure. So it sounds like it should be okay. Then replacing the
> > galvanized drain pipes with plastic and leave the cast iron sewer line
> > alone.
>
> Cast doesn't act quite like malleable iron, no, because it has more carbon.
>
> But, the prime reason is the difference in wall thickness--there simply
> is a lot more material in cast iron than in Sch 40 pipe. For a 4", cast
> 30-lb test (the lightest common), wall thickness is 0.35" while for Sch
> 40 it 0.237" -- nearly 50% thicker. Consequently, it has a longer life
> in general. Also, owing to being used almost exclusively for waste in
> residential usage, it is non-pressurized whereas water service piping is
> under pressure, accelerating any leak.
>
> There's a current other thread of a poster who has leaking cast mains,
> so it does happen.
>
> But, I agree w/ the other poster of "if it ain't broke, it don't need
> fixin'" unless you've already got it torn up and just go ahead or are
> doing extensive work that will be in the way if there's need for repair
> in the future.
>
> --- Hide quoted text -
>
> - Show quoted text -
sorry my main soil stack is 57 years old, and rusted thru leaking.
if your into it anyway replace with schedule 40 plastic. except
indoors in living areas, cast iron is quiet, with plastic you hear
every drop.
cast iron just fails slower
coming soon to this home, replace the main soil stack:(
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