Here is a picture of the single point drains and fresh water tank that is under the passenger bed. The first line on the left coming out of the tank is the fresh water supply line that connects the tank to the water pump. Notice the valve on that line is positioned parallel to the line (Open).
The next line coming out of the tank is the tank drain. Notice the line comes out and immediately is plumbed downward. That is the discharge line that drains underneath the RV. Notice the valve on that line is positioned perpendicular to the line (Closed). To drain the tank, open this valve. Be forewarned -- the tank drains REALLY SLOW.
If you notice further to the right in the picture, you will see two more valves, both positioned closed, on a blue line and a red line. These are the single point drains to drain cold water from the cold water lines (blue) and hot water lines (red) when you winterize.
Speaking about winterizing, that blue line sticking up in the air with the white cap on it is the antifreeze syphon line that you use when you winterize. You connect the antifreeze bottle to the top of the line and then you run the water pump to syphon antifreeze into your water lines. You also have to reconfigure the water heater bypass lines under your refrigerator behind that louvered access panel so that you don't try to syphon antifreeze into the water heater when you winterize -- it's just a waste of 6 gallons of antifreeze.
I have compiled and edited a Vegas/Axis Owners Manual that contains a host of information that is not in the generic Thor manuals. Send me an email to firstname.lastname@example.org
and I'll send you the electronic file for the manual.