Hi from England! I'm pretty sure Arthur Hayes has guessed the same as I, there's a two-way switch for the main freshwater pump located by the side of the sink in my bathroom. If you can look out to the switch bank above the cooker you may well see the red LED light go on as you switch it in the bathroom.
If you (or an assistant) can see that happen, go to the cooker panel and switch the 'pump' off there, then try the switch in the bathroom again. I'm sure you'll see the pump LED come on again. Waste water's gravity fed to the black tank from the bathroom. Of course, this only refers to my model...a SV DP type, but it seems to be a Gulfstream thing. Good Luck. Tom.