Curly Sue wrote:

As to the root penetration, the cost of replacing the sewer main is
much, much greater than giving the roots a haircut once a year. It
would be a 30-year payback. Neither plumber nor sewer guy suggested
replacing it at this time.

You have to take into account that the roots continuing to grow into
the pipe will greatly shorten its life expectancy. Once you have a
catastrophic failure, your options for repair become more limited. Also
your house will be uninhabitable till you get a repair, and that cost
has to be considered.

I had a bad root problem. We were lucky that I happened to be puttering
in the basement each time the overflow occurred such that it was
quickly minimized and nothing of value was damaged, however I
considered the real possibility that we'd not be so lucky in the
future.

Like you I did a cost/benefit/payback analysis. Once it got to 4 clogs
per year, I placed a value of $500 on each clog just for the disruption
to the family for not being able to wash dishes, flush, brush and
shower on the normal schedule (which had repercussions on our jobs) and
the inconvenience of cleanup.

We had a video camera analysis, and based on the sizes of the roots in
the pipe I figured we didn't didn't have more than 2 years before one
of the terracotta pipe sections split and collapsed, necessitating a
costly and disruptive trenching operation. So I added the cost of
losing trees and shrubbery and relandscaping to the cost of "riding it
out" instead of replacing it now, because those were avoidable costs. I
came up with the result that replacement within a month or two was the
most cost-effective, using one of the following technologies:

http://www.zoompower.com/bursting.htm
http://www.perma-liner.com/lateral.html

Note:
Both above technologies need to feed something through the existing
pipe, which is not possible once the pipe is collapsed. After a
collapse, there is no option but to dig out the collapsed portion.

I had the pipebursting one done. Replaced 10 ft of cast iron and 50 ft
of badly rooted terracotta. The new lateral will probably outlast the
house.

Both of those links above show a pit dug next to the house. In my case,
it made more sense to cut the slab floor of the basement so as to pass
the new pipe under the foundation. That was a 4 ft deep hole, as
opposed to 12' deep in the front yard.

To research this yourself, search terms for Google are

sewer lateral
trenchless
no-dig
pipe-bursting
relining
cured-in-place liner
CIPP

in various combinations.

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