We recently purchased a 20019 Trail Runner and were working on sanitizing the fresh water system as it sat for a prolonged period prior to us purchasing. I located the drain for the fresh water tank, however when you turn the valve, the tank will not drain. Thinking there was a blockage; I tried running a strand of 14 gauge romex, no blockage in the valve, however the romex will not make the 90 degree turn in the pex. I used a compressor set at about 25-30 psi, I can hear the air going into the fresh water tank and hear water bubbling when water is present in the tank, but still no water will drain. Does anyone have any thoughts or ideas, or encountered this? Any input would be greatly appreciated.