So... you want to drain your water heater in the spring to get rid of anti freeze, or just rinse out the sediment, or just to get stale water out.
I fill the water heater tank with water first, by putting the winter bypass in normal mode, then turn on the pump, when the pump stops running , I turn the pump off. Then I unscrew the drain plug.
I forgot to run the hot water after I turned off the pump, to depressurize the system. The projectile plug missed me by a mile when it shot out at a surprisingly fast rate of speed. Luckily I found it in the grass. I only got a little wet. I could have lost a nut, or as it is called in the owners manual…a drain plug.