“ I have a rental house and the tenant has parked in the backyard without my knowledge. The big issue comes now that my sewer line is crushed due to their use of the backyard as a parking area. I would believe that I am not held responsible to pay for these repairs but would like your answer on this matter. I live in Wichita, KS and the rental is located in the same city. Please send me an answer and any other information as to my responsibilities in this situation as the landlord. Thank you for your time.”
As a general matter, tenants are not supposed to commit “waste” while they are in possession of the property. Waste is a technical legal term that includes things like causing undue damage of the type you describe.
So, assuming you can prove that they caused the damage, it should be their responsibility to deal with the cost. Whether this debt is collectible is, of course, a separate question.