Hi, I have a 2010 Cougar and I have a grey water tank and black water tank with two pull levers, one for each grey and black, all near the front of the RV. Also in the back of the RV there is a sign on the side that says "Grey Tank" and another pull lever. I have no clue what this one is for. Nothing in my RV materials explaining it. Is it a third tank, (second grey tank)? Odd. The grey tank up front services grey water from the shower, bathroom sink, and kitchen sink. What is this mysterious one all about? I live in this RV and it has not been on the road while I have owned it.