I would run on city water until I was confident everything was looking good. Then I would run the FW pump. When you turn it on it should not run very long if at all. Then shut of the city water pressure. Try flushing the toilet and listen for it to come on and shut off (without pulsing) after the flush. The RV could need all the lines filled. Additionally, ensure their are no leaks inside and out. Good luck..
Don & Dona W/yorkies Gizmo, Master Chief, & Tali
2011 Flagstaff 8528 BHSS 2015 Ford 6.7 XLT
2010 Full Timers & Still Going