I recently added salt to our pool to soften the water because my kids liked the feel of our friends saltwater pool. Based on several online pool volume calculators, which returned 17000 to 23000 gallons, I estimated 5 bags would raise the salt level to 1800. I did not measure the salt level before adding it because I assumed it would be 0 since we have never added salt, but when I measured it a few days after adding the salt it was 3000ppm. So either there was already salt in the pool, which I doubt since it was drained and refilled 5 years ago, or my test kit is off.

So to get to my question, what is the best method of calculating the volume of water that my pool holds? The pool is 30' x 18' grecian shaped with a hot tub.

Thanks,
Zach