Poop in outside sink

Little update here...got everything fixed up and also installed a metal tail-piece so they can't get into my trap again. I see all the messages about sinks tied to the black water tank and it was odd to me as well but now that I know, I followed another's post that indicated they turn the outside sink on before pulling out to put more water in the black water tank. I used to sit there with my foot on the toilet supply to add water...SO MUCH EASIER NOW. As indicated, the more water in the black water tank...much easier to get a clean dump! Thanks for everyone's post here!