The upstairs toilet began to leak and I decided to fix it. In my investigation I found a number of problems. Here is what concerns me. The toilet drain Y's off to the vent. The vent appears to be a 3". After removing a section of the floor I found the drain for the 2 sinks share the same line (3") but in the center it Y's off to the main line that is smaller (2"). The Y is pointed to the sinks. This means the sewer water from the toilet must go down the 3 inch pipe and then make a 235 degree turn to get down the smaller drain. Is this right? Do I need to replace the smaller line or can I T into the larger line or reverse the Y?