Roaches inside my home
Roaches live inside your drains, especially if you have cast iron drain pipes. Roaches live/nest inside septic tanks and man holes, then they run inside the pipes into you home or commercial property. P traps are full of water and if they become dry, the roaches can walk right out of the drain pipes and into your home living space. A crack inside the cast iron is also another signal of how roaches got inside your home, their has been cases of 30 or more roaches under kitchen sinks because there is a crack under the concrete slab, and the water makes a sink hole under the slab, allowing the roaches to craw up into your home living space.
Get a Backwater valves installed to stop them marching in !