In the state of Illinois does a backflow regulator have to be installed in basement apartments?

I recently moved into a newly constructed basement apartment. I also participate in the HUD program. This apartment was inspected and approved by HUD officials. However, everytime it rains my plumbing backs up in the bathroom and floods the apartment. The landlord admitted to me that there was no backflow regulator put into the plumbing and that is why the plumbing keeps backing up. It's been over a week and the landlord will not fix it nor return my phone calls. Wouldn't the county require this fixture if the aprtment was done with a permit (right now I am hightly doubting he got a permit)? It's adams county in illinois by the way. Wouldn't HUD have checked to make sure there was one installed in the apartment. I've been trying to get ahold of my caseworker but she won't return my calls either.