Well since it has worked before, pushing air in a low psi (5) would probably clear obstructions in the fresh water tank drain connection. To make sure any of the water system does not get pressurized, I would open a tap on the kitchen sink, remove fresh water fill cap and then push air in drain for a few seconds and see if it clears obstruction.
2011 Rockwood 8319SS with ProPride 3P hitch/GoodYear Marathons/TST TPMS 507
2008 F250 Lariat CC SB 6.8L V10 4.10 axle ratio (NITTO TERRA GRAPLER G2 LT275/65R20E)
Yamaha 3000iseb generator:Progressive Ind. EMS-HW30C : Eastern Ontario
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