black tank flush lines
can anyone tell me where the tank flush line back flow preventer is located
for the black tanks on a 2018 sierra 384 QBOK. I put flow meters on both lines and still not getting any flow to the tanks. I have flushed the tanks many times by way of holding the toilet flush pedal down to flush the tanks after dumping black tanks. Also tried filling the tanks up several times past 2/3 full and flush and still cannot get any flow at the tank flush connections, I'm convinced the back flow preventers are in backwards.