We had something similar done recently. I had an
idea very similar to what you're thinking -- to push
PVC through and out to the main sewer hookup. A
plumber told me that wouldn't be legal. That makes
sense, since a smaller pipe pushed through would
not yield a sealed drain connection. There would
probably end up being sewage flowing outside from
the end of the pipe.
What we have are 2 or 3 foot sections of clay pipe.
They had shifted a bit and were getting clogged
with roots periodically. In the process of getting it
fixed I learned something interesting: The sewer
cleaning people who were charging $300 to ream out
the roots only use a small bit to make a hole. They
don't actually clear all the roots from the inside of
the pipe. As a result, that needs to be done every
6 months or so. For anyone doing that a better
solution might be to get a commercial grade, 50'
reamer with cutting bits and maintain the drain
themselves. Such a tool is about $500, I think, so it
would pay for itself on the second use, and the reaming
would last much longer than one gets from the
sewer cleaning people.
The final solution was overpriced. It was $4,600
for a crew of about 8 men, but most of those men
were not necessary, and most of them weren't actually
doing anything aside from handing a wrench to the
boss. It took a few hours, then one man stayed for
a few hours more. But the price is typical. It's based
on a rate of $100 per foot. The solution is clever. They
first run a sleeve into the old pipe, after having thoroughly
reamed out all the roots with a number of different
cutting bits. The sleeve then somehow gets pumped
with a liquid. I don't exactly know the details. Then they
inflate the inner sleeve to push the liquid against the pipe
and they cure the liquid, with heat, I think. The result is
a tough plastic pipe that looks to be maybe 3/16" thick,
which is molded to the old clay drain pipe. No more roots
because they no longer sense the water. As part of the
deal we got a DVD movie showing the length of the finished
drain pipe. :)
It seemed like a very good solution, though it's only been
there a year so far. I think the companies are price gouging,
but probably because they can get away with it. To open up
the ground and run new pipe to the street costs in the 10s
of thousands, so the liner is cheap by comparison. And of
course these are plumbers getting plumber's rates.
One limitation, though: In our case the clay pipes had
separated a bit and the sealant between them was gone,
but the pipes were still OK. In some cases the old pipes
will be collapsed, badly broken, or rotted away. In that
case I'm not sure they can use the plastic liner. The whole
thing would probably have to be ddug out and re-piped.
On the supply line, I don't know. If you're hooking up
to municipal supply you're going to have to talk to them
to see what they allow.