Pre 2019
The Black “T” Handle under the sink is the fresh tank drain valve – by pulling that it will relieve the fresh water tank.
There will probably be alittle left in the tank even after draining – the best way to get the water out is to tilt the trailer towards the backend as much as the tongue allows it to angle the water towards the outlet side where the drain is.
We would advise raising the front of the trailer as much as possible, pulling the Black drain valve open/up, and the allowing the water to drain.
2019- Present
Under the trailer behind the driver side wheel is a valve connected to a blue pipe. To drain the fresh water tank just open that valve.