Improper Sump Pump Discharge

I was inspecting a 20yr old house last week and when I entered the home I could smell sewer gases, I thought because the house was vacant for 6 months that it just needed to be aired out. Upon entering the basement I found that the sump pump was dicharged into the main sewer line. This is a big problem for several reasons. 1) The sewer gasses entering the home can make the occupants sick or worse because the gases could contain methan. 2) This is the lowest point so if the sewer line backs up it is heading straight for the sump pump and the the basement floor. It may not back up if there is a back check valve installed, And in this case they did not have one installed. As you see in the picture the home owner removed the clean out cap to allow for the discharge hose, Then they shoved a rag around the discharge pipe to help prevent the odor from entering the home, However that did not work. I was very puzzled by this set up because there is a hole in the foundation wall from the builder to allow for exterior drainage of the sump pump.

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