We have lived in our newly built home for one year. We have a bathroom upstairs and one in the basement. The home is a bi-level with a finished basement...The downstairs toilet does not like to hold water in the tank periodically.....The system got bad in the last three weeks and actually clogged up. The toilet was barely flushing, so I called a plumber....in the mean time I ran a load of wash....what a mistake all the water came up the toilet downstairs and flooded my family room. The plumber came with a snake and got the toilet flushing again.....Three weeks later we noticed the downstairs toilet is starting to slow down again....so I ran a load of laundry and when it first drained the toilet girgled and sucked all the water out of the toilet and now seems to work well again....is holding water. We had a contractor come in to see what would be the problem.....he has no answer for us....we are afraid eventually it will flood again.....Any ideas what we can do?? or what would cause the problem?