My son-in-law has a Salem trailer. The 3"pipe from toilet to tank looks like it goes to about 2" from bottom on tank. Therefore the toilet solids will not flow out in the tank. I think the pipe needs ...
The pipe may be glued and may be inserted into a rubber bushing. In my RV it is glued. You will need to remove the toilet and take the screws from the flange to find out.