Drain Pipe

Inspected a house with a septic tank today. Inside the house there was a perimeter floor drain system around the foundation wall that drains to the sump pump well. When running water in toilet, sink, and tub I noticed the water was coming into the basement under the block foundation into the perimeter drain and sump pump. I have never seen this before. Why would you want waste water coming back into the house. I was unable to see the septic tank lid. There was a 3" pipe outside with a cap on it and a black rubber hose coming out of the ground at against the foundation. I was unable to see the end of the hose. Help

Ya got main drain problems Bro how loud can you say plumbing contractor