How high above grade is the disconnect?
Is the heater listed to be installed outdoors?
Man, I'd like to be in the valve bizz! I count six in that photo.
Bypass flush valve a must, ever year get out the bucket, sump pump, vinegar https://www.youtube.com/watch?v=8-ts7XuvS48
Is that a 2 pole switch? Dollars to doughnuts the WH install instructions call for a dedicated circuit