After my second use of the onboard fw tank system. I began to get air in lines. Consultation of others threads pointed me in several directions (all rather obvious to one comfortable with plumbing!) What I found as the cause was startling. The suction line from fw tank to pump inlet had a small clean hole 1/32 of an inch drilled through it. The location of the hole was covered with degraded floorboard sealing caulking. Close inspection of location ruled out accidental perforation. This perfect hole almost suggest worker sabotage during the construction of my 2013 Rockwood pop-up. Several other construction and quality issues (remediated myself!) only lend credence to a seriously disgruntled worker.
I can try to send pictures to anyone interested! (I say try, as I am not as proficient with computers as I am with plumbing