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Pool Water Salinity Info and Calculator

This calculator requires the use of Javascript enabled and capable browsers. This script is designed to assist in the process of determining how much salt must be added to a pool of water to achieve a desired salinity. "What is salinity?" you asked... (You did ask that didn't you? Salinity is a measure of total dissolved salts in sea water. Formally, it is calculated by weight as the amount of salt (in grams) dissolved in 1,000 grams (1 kilogram) of seawater, though there are other methods of practical determination of salinity, such as by volume, as in this calculator. This is usually handled automatically by saline systems but can be done manually with the assistance of our calculator. There are several converters within the calculator to provide for conversion between US gallons, Imperial gallons and liters, and to convert the designation of salinity from parts per thousand (PPT), parts per million (PPM) and percentage (%). Most salinity testing readers designate the amount of Total Dissolved Salts (TDS) in PPM; some are in PPT and a few are in percentage. Virtually all swimming pool measurements are designated in PPM for salinity. Most large aquarium measurements are in percentage. The other environments vary in designation, as do tester results by manufacturer and testing procedure.

Here are a few common benchmarks and some useful trivia as a reference (weights are based on distilled water; yes, saltwater weighs more per volume than fresh water):

The average ocean and sea water salinity is 35PPT, also known as 3.5%
The Red Sea is the saltiest at 4.25%
The Baltic Sea is the least salty at .7%
The Great Salt Lake in Utah varies in locations from 11 to 33%
The Dead Sea (really a lake) varies from 26 to 35%
The Salton Sea in southern California is 4.5% on average
Fresh water is less than 1PPT
Brackish water is 1 to 25PPT
Hypersaline water is greater than 40PPT
Human tears are 9PPT
Current saline swimming pool systems are 2800 to 4000PPM
Older saline swimming pools and therapeutic systems are 3500 to 6500PPM
Salinity (PPT) = Chlorinity (PPT) x .80655
1 liter of water = 1000 grams or 1 kilogram
1 US gallon of water = 8.3452641 pounds or 3.7854118 kilograms
1 Imperial gallon of water = 10.0222443 pounds or 4.54609 kilograms

Enter the Current volume of water in the pool being tested, in any of the three designations. That may or may not be the maximum volume. If you are adding water, enter that volume also. Then, enter the beginning salinity and the desired salinity. If you are filling an empty pool with fresh water, the beginning salinity would be zero (0). If there is already some salinity to the water, test it and fill in the appropriate value in the appropriate designation from your tester. Enter your desired salinity, for whatever your purpose. Click on Calculate and all values determined will be displayed to 5 decimal place accuracy. Because of variables in the volumes, readings and salts, and factors such as the evaporation rate (60 inches a year here in Palm Springs), the calculated values are always approximate but are still accurate enough for pools, ponds and aquariums. Our volume defaults are for a small swimming pool or a large therapy or tide pool, with no additional water being added initially. The default salinity is for ocean or sea water. The beginning salinity is for TDS but additions should be in pure non-iodized salt. You might also wish to use our Water Weight Converter.

Required Data Entry
Actual Current Pool VolumeUS Gallons  Imperial Gallons  Liters 
Added Water Volume To CurrentUS Gallons  Imperial Gallons  Liters 
Beginning Salinity PPT  PPM 
Desired Salinity PPT  PPM 

Calculated Results
Water Volume Total US Gallons
Water Volume Total Liters
Water Volume Total Imperial Gallons
Water Volume Change Percentage
Water Volume Change Percent
Salinity Net Change Parts Per Thousand (PPT)
Salinity Net Change Parts Per Million (PPM)
Salinity Net Change Percentage (%)
Required Salt Addition Pounds
Required Salt Addition Ounces
Required Salt Addition Kilograms
Required Salt Addition Grams
Updated 8.12.11

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