Thank you very much!

I am still very confused as to why it says that I have a 21,000 gallon pool in my signature. I have an in ground 18x38 pool 3ft shallow 8ft deep, roman shaped with bumped out step. When I use online pool calculators, they indicate a 28-29,000 gallon pool, and the company that takes care of our pool says it is 33,000 gallons. I usually average everything out and say 30,000, but I want to make sure that I have all of the values correct before I start adding chemicals. It just seems like it is a huge difference. Thanks, again!!