That is one way to tell that you need to dump the gray water tank, when the water backs into the shower pan.
Idiot lights for gauges are not reliable and most do not work anyway, specially the cheap ones in C class RV's, mine quit about the 3rd month and I have not used them since 2002, grey water backing into tub, time to dump grey.
Black water showing in toilet tube time to dump black tank, in any case my wife can hear the noise change when the black needs dumping, she is one hell of a sensor.
navegator
