I have a formula for calculating the amount of sodium bicarbonate to add to pool water to achieve a desired increase in the total alkalinity of pool water which works perfectly and here it is: 1.5 multiplied by the factor for gallons of water in the pool (30,000 gallons is 3.0, 20,000 gallons is 2.0 and so on) so let's use the factor 3.0 in this example, that answer multiplied by the desired increase in total alkalinity in parts per million so let's use 20 ppm in this example so we would multiply by 20, and that answer divided by 10 to yield the lbs. of sodium bicarbonate (9 lbs. in this example) to add to the pool water to achieve the desired 20 ppm increase in total alkalinity. I used to have a formula for calculating the gallons of water in the pool by knowing how many lbs. of sodium bicarbonate I added and then measuring the increase in total alkalinity of the pool water but I lost the formula and would love to have it back. So let's say I add the same 9 lbs. of sodium bicarbonate to the pool water and it raises the total alkalinity of the water by the same 20 ppm. Can someone tell me how to turn the formula around to yield the gallons of water in the pool? This really helps on irregular shaped pools. 