2003 Pleasure Way Traverse Grey Water Tank/Valve

I've recently purchase a 2003 Pleasure Way Traverse, which has been great thus far. However, I can't locate the grey water tank and valve to drain the waste water. The very brief manual says the tank is "located above the floor under the microwave cabinet". However, there is no access to this. Then it says "open the valve for the grey waste tank". But I don't know where this valve is. I have hooked up the sewer hose to the coupling for the drainage, which is underneath the floorboard on the side. Any idea where this valve is?