In every state in this country, the seller of real property is required to disclose all items that are known that could materially affect the price paid or the desirability of the property to a willing buyer. If you can prove that the sellers knew of the sewer line problems of the home they sold you and they did not close this material fact to you before close of escrow (and you had no knowledge of this), you have a claim for concealment (fraud) against the sellers.Your damages would be the current costs of repairs of the sewer line or the diminution in value of the property at close of escrow (lesser of the two amounts).