Repipe to main sewer. surprise septic tank

[Avi Lah]

I bought a house last year after inspection 

A general Inspection report showed everything is ok with the plumbing. nothing came up. 

last month I had some warer backout issue coming up from the bath in the basement, ordered a plumber.  The fix the issue and installed a cleanout which was not there

But- Was a big surprise They told me - the sewer pipes connect to a septic tank not to main sewer line without permit. Should be connected to main sewer system and have it inspected. require re-piping the basement so that all plumbing empties into the public sewer line instead of the septic tank which need to be flash out. 

This cost 9k usd + redo the bath in the basement.

Nobody told me that when i bought it. Anything which i can do? Inspection didn't showed that (it was general inspection not a sewer inspection)  the seller didn't know its like that. 

[Chris Seveney]

@Avi Lah

99.99% of these you will have to bear these costs as most states are buyer beware and the seller may not have known.

If this was done to my house I would have had no idea as I bought it the way it is

Also an attorney to pursue this will cost you more than the fix and again you would have to prove the seller knew about this and willfully withheld it from you.