Pool size based on salt add

[devroute]

So I've been running along for 2 years thinking my pool is 18K gallons or so. Each time I use the pool calculator to determine how much salt to add it is telling me to add almost 2x as much as really needed to reach the target level. The first year I ended up adding too much due to this.

For example, this past weekend my salt level was 2500ppm and this was verified with a salt test strip and same reading on my Aquapure. The pool calculator said to add 78 pounds of salt to get to 3000ppm. Instead I added only a 40 pound bag and I ended up hitting 3000ppm right on the button, again verified with test strip and Aquapure. So should I assume my pool is only 10K gallons? (Pool calc says a 40 pound salt addition will move a 10K pool from 2500 to 3000).

For comparison when I add CYA & MA it is much closer in calculations, still a little overshot but not by much. Just trying to see if I can trust the salt and my pool is smaller or not. The size of the pool is a bit unknown since it was built by previous home owner. I do have the records and it seems like closer to 20K gallons of water was the fill.

Thanks!

 

[duraleigh]

What are the dimensions of your pool? I would start there.

 

[rdmustang]

I know exactly how large my pool is (down to the gallon) and the pool calculator tells me to add about 25% too much salt. It could also be a combination of bad tests (salt tests are notoriously inaccurate) as well as other chemicals adding salt (bleach for instance).

 

[devroute]

The pool is rather irregular shape, spa is easy calculation though, I'll eventually take the time to try and calculate it out. I was just trying to see if using the salt recommendations would be a good way to determine pool size. But as rdmustang mentioned he gets a higher recommendation as well.

 

[YippeeSkippy]

I would use chlorine as a better test. After testing the pool, add an amount that Pool Math tells you to add to increase it by x amount (say 3?) and after adding that much test your CL again. You might see it is spot on, or if chlorine level too high=a smaller pool. If chlorine level didn't hit the right amount that implies that the pool is larger than you know.

 

[duraleigh]

I know exactly how large my pool is (down to the gallon) and the pool calculator tells me to add about 25% too much salt.

I don't think PoolMath is making that mistake. did you take into account the existing salt in your pool before you dosed?

For what it's worth, I do not like any chemistry method to determine volume.....far too many variables. Measure your pool and post a pic if you need to know volume. Lot's of math folks here to help out.