I believe the water serves a couple of purposes. 1) Spreads the heat evenly around the fat and helps speed the rendering.
2)Keeps the heat below ~212 degrees and keeps the fat from smoking and any meat bits from browning, leading to a cleaner tasting fat.
Sent from my SGH-i917 using Board Express
Traeger lil Tex, 2 Weber 22.5", UDS
Mop, Sauce & Two Smoking Barrels BBQ Team
They call me "Dave"