I recently bought a house that was built in the 40's. The previous owner finished the basement but never pulled the permits or completed anything to code.

We're having a hard time with the bathroom in the basement. The shower, toilet and sink overflow with raw sewage (it's disgusting) or the set up acts really strange (gurgles, clogs, won't drain, bubbles) whenever we get a rain.

The town did not install backflow regulators, even though the house sits below street level. Does anyone know whether these are required to be installed at the house-level, or if one was installed when the house was built in the 40's is it likely to fail over time?