I had 2 weeks to find a house to buy AND move 350 miles away. This problem was undisclosed by seller. Both toilets over-flowed when solid waste is ummmm, in the toilets. Plumber told me that it was because the toilets were from the 1990s. He wouldn't let me chose the new toilets. He put in Gerber Viper ADA toilets. Problem was not corrected and the handles on both toilets go down half way sometimes and there is a weak flush then. One of the toilets runs for about 35 seconds before it shuts off. Plumber returned and increased the fall of the pipes in the crawl space by 20%. I've now paid near 1500.00 and I still have the same problem. The plumber said that he would look at the stack next. There are new pipes from the house to the road, no trees near the house and when the man looked in the cleanout he said it looked fine. I'f I put a cup of Dawn dishsoap in the toliets and flush with a pail of hot water, the waste goes down. Any ideas what the problem could be? Should I ask him to look at the stack? Thank you.