I drain my system and fill with the pink RV anti-freeze, and pour some in each drain (water heater bypassed and annode pulled). Blowing out the lines get most of the water out out, but not all. Heck, have you ever taken a drink with a straw and blew it out? There is still residual fluid on the inside of the straw and it's a perfectly straight 8" tube, can you imagine how much is still in a RV water system? Pink RV anti-freeze is still needed unless you live in the south with only occasional freezes. I'll spend the $5.00 a gallon for piece of mind during my long winters freeze.
