Seller Didn't Disclose a Major Issue - Now what?

[Stacey Lancaster]

Hello, we recently bought our first STR cabin in Gatlinburg. After the plumbing backing up three times in the last two months with just normal use, we have had two plumbers confirm that the main line is clogged with broken pieces of toilet. This cabin burned down during the Gatlinburg fires and was rebuilt using the original plumbing lines. The toilet most likely exploded during the fire and pieces of it fell into the main line. The cabin was rebuilt in 2017 so there is no way that the sellers didn't know this was a problem.

The plumber is not able to remove all the pieces because some of them are large and won't make it around a curve in the line.  The solution is to excavate (under a massive storage building no less) and replace the entire line to the tune of $3,000-4,000.  This is in addition to the almost $1500 we've spent already.  

I'm not sure what my next steps should be?  Any suggestions?  

Stacey