Basement Flooding / Sewer Back Up

[Ben Nantell]

Hey Y'all,

Wondering if anyone in here has had experience with back flow flood prevention systems? I had one installed 3 months ago at my property in Chicago. Recently due to the heavy rain my basement flooded again. I'm waiting a diagnostic review but based on my experience of the flooding issue, the flood prevention system was either installed properly and did not work, was damaged during the back up or couldn't hold the pressure. 

The backup occurred the same as before. The main city line backed up into my line, somehow got passed the flood prevention system and eventually coming back up through the shower basin and kitchen floor drain. 

Any thoughts / ideas on how to handle this with the plumber? He responded saying that they cannot guarantee never having a backup issue again 100% but this isn't a 10 year old system. It was installed and less than 3 months ago. 

Thanks again! Cheers - Ben