We have had a green pool before and never emptied it. I also had a coffee colored pool when switching from Bacquacil (spelling) back to chlorine. I don't know about your area, but we have a great pool store right in town that tests the water and can tell us exactly what to do to clear it up. It's still early in the season and I hate to see you put all that water down the drain. We have problems here with oak leaves and even though we cover it, we still end up with them on the bottom of the pool slimy and gross. Emptying the pool would work I guess, but I would really get professional advice before doing it.