The question is....should I replace my cast iron sewer line outside with PVC?
Here is the story....
Building a pond directly above the line. The pond will be almost 3' deep, the line is 4'+ below grade. The house was built in 1915 and I'm sure the line is original to the house. The cast inisde has, and will be, all new PVC to 4' outside the foundation wall to a PVC cleanout.
The cast taken out of the house looks like some of it has started to corrode through, but the inside walls aren't horrid. I have exposed about 4'-5' of the cast that will be under the pond, because I wanted to see what it looks like. The part exposed looks very good. No visible cracks or rust. There is a small playground/deck area along the back 25' of my lot, so I can't replace that, which leaves about 30' of possible line to replace. Some of which is under a HUGE Silver Maple.
I should also note that when I bought the house from a foreclosure last April I had to have it snaked within 30 days of buying the house and 45 days later, I had to have plumber out again to get another backup taken care of. The 2nd time all they did was use a bladder to clear a clog. We then put root killer and something else down the drain and haven't had any issues in the last year.
So with all of that and given that I will be within about a 1'-2' of the line for 16' of the line, should I just do the extra work and dig it out and replace it while I'm there or just leave it alone and not fix what isn't yet broken? Even though the cast is about 100yrs old. I've had 4 people say they wouldn't mess with it, but none of them are experts or plumbers. One is a neighbor who lives 4 houses down and just opened his line up to tie into it for a garage and said his was clean.
Thanks for any input here, I don't know what to do. I don't mind the digging, but don't necessarily need the extra work.