Sewer back up suggestions: Despite living on the corner and thus presumably being the 'end of the line' on the sewer, we haven't had a problem until this last week as far as back up occurring after a heavy rain. The strange thing about this time is that even after a few days with no rain last week, there was still a visibly high level of water underneath the basement drain. As a result when it rained again yesterday, presto, more back up. It's not a lot of water but where poo is concerned, any is too much. I was thinking about putting some of those one-way drain valves on the existing basement valves to stop the back flow but I read that this can increase pressure in your sewer line possibly leading to a break. Anyone else have suggestions? I presume calling 311 is a waste of time.