Question 610599
Assume 45 gallon pool (just to get a rate)

fill rate = 45 gallons / 45 hours = 1 gal/hr

drain rate = 45 gallons / 60 hours = .75 gal/hr

NET FILL RATE = fill rate - drain rate = .25 gal / hr

Time to fill pool w/ both pipes on = 45 gallons / .25 gal / hr

180 hours