Are there more than 2 drains on '99 3023?

I tried to drain the plumbing system on my recently acquired 1999 3023. There are only two drains on the left side on the rear. I opened the sink faucet, both hot and cold and opened the faucet the the bathroom. But there is STILL antifreeze in the lines under the sink and hooked up to the water heater. On a different thread there was a schematic of the plumbing system for a 2002 2027 showing 4 drains, does the 3023 also have four drains?
I have attached some photos, there was some sort of short hose on the floor of the cabinet where the water heater is (photo enclosed). What is this for?