2&861 Combining grey tanks?

[Russmd]

I have a 2861DS. It has the standard 50 gal grey water tank and then a completely separate smaller (? 20 gal) tank just for the outside galley sink. The main grey water tank fills very fast. The galley tank rarely has anything significant in it. The outlets for the main grey and black are combined inside the compartment, the galley tank outlet is added on, under the frame just aft of the sewer compartment.
I'd like to install or rig something such that if/when the main grey water tank is full, I can open a valve and shunt some of that water into the galley tank.
Again, the outlets are separate and note the same compartment, but close.
Ideas?

[Joshua Cavitt]

You're going to have to have lines that go from one tank to the other and enough pressure to carry water from one tank to the other. It won't be easy but I'd like to see if it could be done.

[Russmd]

Yes, that's what I expect, but I'd like to know if anyone has done it. In the attached photo, the grey tank is above left, inside the compartment. The galley tank is below right with the actual tank strapped on underneath. The galley tank is well below the grey tank. I think an easy solution, however inelegant, will be for me to just run a short drain hose between the two outlets when necessary and let the upper grey drain into the galley tank when necessary.