I have the herbie on my 300 and love it you just get a little trickle down the emergency I dont have the gate valve on mine it just makes it easier for tuning than a ball valve like I have .
My drain it like this one. On my emergency it drops down to a 45 degree, pipe goes over to the drain section and another 45 degree down into the sump. Andy ideas on at least getting the emergency drain to be quieter?