"Eric in North TX" wrote in message
...
On Jun 21, 1:55 pm, "MiamiCuse" wrote:
Recent video inspection revealed that my 40 year old cast iron pipe under
the concrete slab is deteriated to the point of needing total replacement.
Some spots the bottom has reduced to nothing, some spots the corrosion
build
up looks like the inside of a cave...two independent video inspections
recommend total line replacement.

I have not yet done the finished flooring in the house, so I guess it's
good
news I found out now.

In order to replace the entire underground line, I can find a way to
determine exactly where it is (no, no records in the city I checked
already), and cut up the slab and hope for the best. Or I can just ignore
where the existing line is and just design a new route.

It seems designing a new route but tying in existing bathroom group has
the
advantage of not having to pinpoint exact locations of the line but only
specific locations where the existing bath groups tie in. And since I am
doing remodeling, 3 of the 4 baths I know where they tie in and I have not
backfill with concrete yet.

Doing a new line has the advantage of avoiding cutting a trench across
existing walls, I can possibly cut a line along a hallway in a straight
shot, but run the risk of running into other pipes below grade that may be
in the way (pool pump lines, supply lines, deck drain lines, roof drain
lines).

What is the ramification to the structure of the slab is it's a 90'x90'
slab
and I cut a 90' lone trench across it?

Is there any sense in not making a single 90' cut, but say 8 10' cuts with
several 2' sections uncut and I try to bridge under it will that "hurt"
the
structure any less?

I am laying in new 4" PVC pipe so the trench would be around 6" wide only
except where I am doing tie ins.

Thanks in advance,

MC

You could bore under the slab and push the pipe from outside. you
would have to do several bores to accommodate the various drains and
an excavation to tie it all together.

I will need to look into that. However, the worry I have is any horizontal
bores will end up cutting or breaking anything in it's way including copper
supply lines, pool pump lines, deck drain lines, roof drain lines, those are
all running under the slab across the sewer line either above or below.