Scott,
Thought I'd jump in here. I used my water bowl, that came with my 18.5, once or twice before I found out
about using sand & a terracotta tray as a heat sink. I haven't used water for years. It's easy to do, just
fill your water bowl full of sand and put it back into your WSM. Then cover a terracotta planter tray with
tin foil (to catch the drippings) & placed the foiled tray on the top of the sand filled water bowl. I have never
looked back! To me it's the perfect heat sink. The sand holds the temp steady, it never needs refilling, my
hands don't get burned trying to refill the water, I never lose heat or create more heat by opening the door
to check the water, etc, etc, etc.
When the grease gets to be a bit much, I un-foil the tray over a garbage bag, and re-foil the terracotta tray.
My 2¢.