Requesting Selling to Compensate on repair

[Ernest Ho]

A few months after close, and after a couple months of rehab, I finally have a tenant move in.  Quickly, the tenant discovered a problem with the sewer pipe.  This was not something the seller had disclosed.  The seller had inherited the property, and did not live there personally.  Some other family members were living there, on and off.  I believe the period between the inheritance to putting on the market was around 2-3 years.  Anyhow, the seller is claiming they did not live there, and therefore did not know about the sewer problem. Roto Rooter said there was a job about 1 year ago.  

According to the neighbor, this was a long problem that orginial owner had known for a long time but have not fixed it.  It was a very familiar issue recognized by the neighbor as soon as they saw roto-rooter there again.

How do I go about claiming the cost from the seller?  I feel the seller has responsibility to find out from whomever living there any problems they know of.

Thanks!