The only pan I ever plugged is my finisher pan. That is 2x6 and has 2 compartments. If I don't have enough to use both sides I plug the pass thru and fill the other side with water. Then I can finish off the small batch in the one side.
Back when I had a 2x6 pleasure model, it did have a slide gate at each pass thru from one section to the next, but I never closed them, I just drew off slowly and maintained steady temp as much as I could. I thought those gates were to be used if you had to draw off faster to prevent mixing, but I feared burning the last section when that level got low.
Dave Klish, I recently ordered a 2x6 wood fired evaporator from A&A Sheet Metal which I will be converting to oil fired
Now have solar, 2x6 finish pan, 5 bank 7x7 filter press, large water jacketed bottler, and tankless water heater.
Recently bought another Gingerich RO, this one was a 125, but a second membrane was added thus is a 250, like I had.
After running a 2x3, a 2x6, 3x8 tapping from 79 taps up to 1320 all woodfired, now I'm going to a 2x6 oil fired and a 200-425 taps.