If you do not flush enough water down the sewer pipe, chances are that the drain pipe cloggs.
The new 1 1/2 gal.. flush commodes can cause this to happen. Therefore, you maight replace the flush valve with one that you can adjust.
American Standard flapper valves need to have the float adjusted to give enough flush water to keep the sewer line from eventally clogging with solids.
The chain mechanism should be adjusted to allow more water to flow after flushing solids.