Like the others have said it depends on exact profile, a traditional 20x40 with equal deep / shallow split is going to be in the 36,000 gallon ballpark, on the low side it may be as small as about 32,000 gallons, either way for now dose as if it were 36,000 gallons, if you get bigger changes than expect reduce your estimate of size next time and go from there.
Hello , This thread has been inactive for over 60 days. New postings here are unlikely to be seen or responded to by other members. For better visibility, consider Starting A New Thread.
Welcome to TFP! For a wealth of pool care information please check out our free Pool School. If you are in need of specific help then we encourage you to Register and ask us here in the forum!