I have Peggie's book on order that discusses all this I'm sure, and I'm probably getting the cart before the horse - trying to design my system without having read the book, but here goes.I am ordering a Ronco replacement holding tank. I've had several discussions about the best location for the outlet. One school of thought is to put it at the bottom of the tank, with a 180 degree u (like the pea trap under a sink) going below the bottom of the tank to facilitate draining. Disadvantages: Waste will always sit in the U, and I have to drill holes to accommodate the U. The other school of thought is to put the drain outlet at the top of the tank, with a dip tube going into the tank to pick up the waste. Any recommendations for which way?