Front water Tank

[Sakoten]

I have a 2004 Bavaria 38 any idea how I use the water from the front tank . The rear one empties but it doesn’t use the front one . Any help gratefully received

 

[yoda]

There is a 2 way valve just before the pump in the heads.
Owners manual here:
https://bavariayacht.org/downloads/manual/Bavaria 38 2002 2003.pdf