Good info...but where is the water pump located on the 2106DS?
Not sure, but a good first place to look, is the front storage locker...if you see an open access space in one of the inner walls, or a screwed panel...it is most likely there. If you see a short length of hose, that is what you'd place into a open gallon of A.F. , after you set the by-pass valve to your potable water tank. If you have the factor installed by pass, and that hose, you WILL have that shut-off valve already installed as well. Same for the water tank by-pass hot and cold, and the two valves that cut off water into, and out of your HWT.
BTW, the most complete method of Winterizing, is to do both venues...blow out your water lines, (through the city water port (with the filter screen removed, and no more than 30 PSI set on your compressor regulator knob)), and then use your water pump in by-pass mode, to push A.F. to all water fixtures. Run your facets, shower wand, outside shower hot and cold, with the hand wand turned on, and toilet foot flush lever, until you see a full pink flow of A.F. If you have an outside cooking centre...make sure that is taken care of as well.
Make sure to also place 1/4 gallon of A.F. into each of your kitchen sink P-traps, bathroom sink, as well as the shower stall., as this will add in total, about the gallon of A.F. that you need in the Grey Water Tank. Place a full gallon of A.F. down the toilet into your Black Holding Tank..and then when you close the foot flush lever...place one to two inches of A.F. into the bowl, to keep your black seal ring, moist and lubricated. Check once a month during the Winter, to make sure the seal hasn't dropped that one to two inches of A.F. past it...as this is a good test of the seal's integrity.
If you ever do see it dry...you will need to obviously fill that one inch of A.F. back up...and in the Spring before you De-Winterize, buy a new seal and/or flush ball kit, and install in the toilet. The toilet should always hold enough water during camping season, to keep the flush seal moist. Never let it go dry, and stay dry between flushes. That one inch of water, you keep over the toilet flush seal, acts like your sink P-Traps...to keep gasses seeping up from the Black Holding Tank, let alone protecting the seal from dry rot deterioration.