Weight or volume


Well-known member
Aug 1, 2010
Columbia, SC
I am working with balancing a spa and a pool. I am using the Pool Calculator for the pool and another calculator for the spa. I am wondering how most people use the recommendations. It seems most of the information is usually based on weight. I learned on the spa (I had it before the pool) and learned using volume measurements. I have tried a scale to weigh the chemicals but the measurements don't seem to correlate.

chem geek

TFP Expert
LifeTime Supporter
Mar 28, 2007
San Rafael, CA USA
Weight measurements are the accurate ones assuming concentrations are known (at least for The Pool Calculator; I can't comment on the other calculator you are using since I don't know what it is). Volume measurements are always approximate and based on a density estimate. You can always measure the weight of a known volume of settled product (tap the cup to settle the contents) and can do your own conversions, but usually The Pool Calculator is pretty good.

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