I had a condo built in a brand new complex about 3 years ago. From day 1 I began to have plumbing problems at the frequency of once every 3 to 4 months on average. Last year, after much documented evidence and pleading with the builder, they discovered that I had a condition known as backwash where instead of the water in the toilet flowing away from the condo into the main sewer line it would on occasion (if all conditions were right, like everyone in my building using water at the same time) would come back up into my condo. It was caused by a sinking of the main line right at the point of the plumbing entering my condo. In any case, last July the builder agreed to replumb that bathroom and the associated plumbing. I have not had a problem since that time and feel that the problem has been resolved. In light of not having problems, is it necessary for me to disclose that I once had this problem to potential buyers. I am afraid if I say something it will deter a potential buyer. HELP!!!! Please advise.