Drain valves

[billtrish]

I have just purchased a 2010 Elkmont and we really like what we see. I have been reading about all the problems other owners have had and the only thing I have found is the infamous leak from the bathroom fan. The only towing experience I have had with it is the 2 hour drive from the dealer to the campground where it is for the warm weather. It towed similarly to our 2720 SL except for getting 2-3 mpg less and driving slower at 60 mph plus or minus.
The main reason for writing, is that I noticed two drain valves at the right rear. What do these drain? Winter is coming and I want to know what's the deal.

[wbmiller3]

Our 2001 2619 trailer has 4 drain valves. Three look alike and drain various parts of the piping system. The fourth looks different and drains the water storage tank. Two are located at the rear of the street side of the camper and two are nearer the front on the same side. If you open a hot and cold faucet inside and then open all 4 valves, your system will be effectively drained of water.

There is more info on the plumbing system in the technical library of this site.