Cast Iron Sewer Line is clogged

[Matt Schambeau]

I have my first rental property which I purchased at the end of July in Roswell, GA which is just north of Atlanta.  It's a small duplex that was built in 1965.  This week I had two plumbing issues.  On one side there was a small leak in the blue poly water main near the meter and on the other side when you flushed the toilet water went in to the bath tub.  Both sides are 2/1's and Hispanic brothers live in each side (one with family and one with friends). 

I had both repaired and on the drainage issue the plumber stated there was women's products causing the issue.  Two days later the tenant called me back with the same issue.  This time the plumber ran a camera down the line and said the house was fine, but the cast iron sewer line from the house to the sewer was clogged with grease so bad he could not get the camera down it.  He game be the following options to get it fixed

1.  $6500 - Replace it all the way to the sewer with PVC I'm assuming

2.  $5000 - Find the bad section and dig it up and replace it.  Then jet the line out

3.  $2350 - Install a 4" cleanout and jet the line (no warranty with this option)

Has anyone dealt with this type of issue before.  Do these prices seem reasonable?  I'm going to try and get a couple more quotes today.  I would like to just do the $2350 option, but he stated that it may not work because we don't know the condition of the cast iron pipe is in.  Then jetting it out may cause leaks in the remainder of the line due to weak spots that are nearly rusted through.  He advised against it and recommended just replacing the entire thing. 

One other thing to mention, is the sewer line runs under a concrete slab/pad in the back that would have to be removed.

I appreciate any advice or help anyone can give me.