I drained a little more than 1/2 my pool, and refilled with tap water. I intend to go with liquid chlorine now, instead of Trichlor / Cal-hypo the pool guys were using.
Just tested results:
25000 gallon inground, vinyl-lined pool
82 degrees (water)
Direct sun from 8am to 4pm daily.
pH: 7.2 (LOW)
All good except pH. I added roughly 32oz by vol of soda ash. (I say roughly because I didn't have an exact measuring tool).