Originally Posted by prairiecamper
If you have tried all 8 suggestions and still no joy, it is probably the check valve at the outlet side of the pump. When the pump builds up enough pressure a pressure switch turns the pump off, however if the check valve leaks back the pressure switch won't turn off the pump. Sometimes you can seat that valve by turning off the pump and using the outside city pressure source. Also if you do that and your trailer potable tank starts filling slowly you will know that it is in fact the check valve. Good Luck
This just went to the top of my check list. Very good suggestion prairiecamper. KyDan suggested a bad pump also.
checking the check valve should be the very next item to do. I have heard of brand new pumps having check valve issues.
2013 Forest River Salem Hemisphere SBT312QBUD
2001 CrewCab F-250 7.3 PowerStroke Diesel
SuperChip, BTS transmission, 6.0 Trans Cooler