2 black tanks?

[Tamster]

I have a 2017 Keystone Hideout 32BHTS that i just purchased previously owned. The bathroom is at the front passenger side, and there is a valve there on the driver's side to empty black and grey. There is also a valve to empty black and grey near the back, which is the one the park connected for me. When I went to empty the tanks yesterday though, the black won't empty from the back one. Is there a bypass I need to pull or something to have the front black tank drain from the back, or would I need another hose for that?

Thanks!

[sourdough]

Both dump outlets will need to be connected- they make a Y you can connect dump hoses from each outlet to one that goes to the septic inlet. The front one is for the black tank. The back one has 2 pull handles for the gray tanks. Looks like there are 2 30 gal. gray tanks. Below is a video of your trailer but a 2016 model - it had the best views and descriptions of the dump valves. At about the 1:15 mark he begins talking about the dump valves.

https://www.youtube.com/watch?v=D2BTdsNnmgY

[NH_Bulldog]

Based on your floor plan, I would suspect that you have 1 black tank at the front, plus 1 grey tank at the front. Then one grey tank for the kitchen sink and 1 small tank for the outdoor kitchen sink. This is also supported by the published specs indicating 60 gallons of grey (2x30) and 39 gallons of black (1x30 + 1x9). If you are pulling the rear “black tank” handle I suspect it only drains the small outdoor kitchen sink tank