draining the grey water tanks

[fordtech 2008]

our first trip with our sundance 3300ck and when we opened the grey water tanks to drain them very little came out,both were showing 2/3 full,opened the black tank and shut it and the grey water tanks started draining, is there a special way to drain them?

 

[JohnDar]

I've noticed that my Gray #1 needs a little coaxing at times. I'll open it, then Gray #2, which flows fast. Then shut #2 and #1 will drain. It's still slow due to the position of the tank relative to the sewer connection. Normally, I dump the black first, then the grays unless only the gray tanks are full.