On one of our weekend camping excursions all they had left was one site left and it was water, electric, and sewer. We just used the sewer drain at the end to dump everything. We noticed all the other sites were all hooked up the whole weekend. Do you open your black and gray tank when you have a hook up like this or do you open one of those for the weekend and dump the one you don't used at the end. Thanks for clarifying for me. 
