RV Repair: RVs Gray Water Tank, piping connections, gray tank

Question
When the gray water tank gets over filled, shouldn't it overflow from the bath tub since any piping connections from the sinks & tub should be sealed? I noticed my gray tank started leaking (reading full on gauge) right after I moved it from the levelling blocks but not before.

Answer
what kind of unit do you have there are pee traps on the sink and tub.but if it is full it will back up a level off just like a kitchen sink if you go to drain it and on side is full and the other is not.but the piping is backed up it will back feed the other sink and level off