More information is needed, including a careful review of the disclosure form and the contract. Feel free to contact me for a free initial consultation. You have to be very careful in assessing fault. It sounds like the inspector did his/her job (the inspection agreements tend to have liability caps) but that the seller both concealed information and gave false information. Realtors have obligations as well.
This response does not constitute legal advice and does not create an attorney-client relationship.
Wet basement cases are notoriously difficult to prove, but sometimes they are winnable. Every fact detail is important and you should consult with a trial attorney to obtain a full evaluation of your case.
You can reach Martin D. Koop at (419) 447-2521 or firstname.lastname@example.org. Martin Koop is an attorney licensed to practice in the State of Ohio. Answering your questions does not create an attorney-client relationship between anybody and Martin D. Koop. You should speak with an attorney to whom you have provided all the facts in your case, before you take any actions or make any choices that may impact your legal rights. I am not obligated to answer subsequent emails or phone calls unless you have formally hired me. I wish you the best of luck with your legal matter.