The valves are on the end of the low point drains. You have 2 drains per side, one for hot the other for cold water lines. Just turn the valve and they will drain. I open the faucets inside so there is no vacum created and they can drain.
I also winterize with air. I just close the valves, hook up to city water connection, put air compressor on 20 LBs, and go around opening faucets until no water comes out, including low points. Run some anti-freeze through water pump, pour some in drains, done. As we do most of our camping in the cold weather instead of summer, we are ready to go.
Make sure and drain the water tank, valve is hard to get to, but is back by the rear landing gear.
