What two manufacturers each declare
Two things, published by two different parties. The salt manufacturer declares a purity — the proportion that is sodium chloride — and states which additives are present or absent. The cell manufacturer declares a target salinity in grams per litre, and a salt specification the cell was designed for.
Both are honest and both are checkable. Between them they answer the only question that matters at purchase: will this sack keep this cell working.
Why 99.9 % is not the whole answer
Purity does not promise suitability on its own. A 99.5 % salt with no anti-caking agent may suit a cell better than a 99.9 % salt with one, because the tenth of a percent is where the difference lives.
Target salinity does not promise a quantity to add. Converting a salinity into kilograms requires the volume of water in front of you, which is not a figure anyone else can supply — and a stated pool volume is not the water the pool holds.
And neither promises output. What a cell produces per hour is its own published figure, and it depends on salinity, on water temperature and on the cell’s age.
What a sack is compared on
Grain size and dissolving time, because a fine salt dissolves in hours and a coarse one can sit on the floor for a day. Pack size and price per kilogram, since salt is bought by the 25 kg sack and the price per kilogram is the only comparable figure. The cell’s stated life, in operating hours, which is the real running cost of a salt pool. And a salinity reading, which means owning something that measures it — several test strips and most photometers do, and the pages say which.
The sack, the cell and the strip
Pool salt, where purity and additives are the two lines that matter. Salt chlorinators, where the target salinity and the cell specification are published and where a page prints them because the sack alone cannot answer the question. And the measuring shelf, where salinity is one of the parameters a strip or a meter either reads or does not.
What readers keep writing in to ask
Can I use table salt or dishwasher salt?
Cell manufacturers state what their cells accept, and that statement is what pages here report. The reason pool salt is sold as a separate product is that table salt is usually iodised and dishwasher salt is granulated for a different purpose — and both questions are answered by the cell’s own documentation, not by us.
What is an anti-caking agent doing in salt?
Keeping it pourable in a sack. It is a useful additive in a kitchen and an unwanted one in a pool, because it does not disinfect, does not leave the water and is one of the things a cell maker asks to be absent. Salt sold for pools states that it contains none.
What salinity does a chlorinator need?
A figure in grams per litre, published by the cell manufacturer — typically somewhere between 3 and 5 g/l, and different between makers. It is a property of the machine rather than of the salt, and the page prints it on the chlorinator rather than on the sack.
Does the salt get used up?
Electrolysis converts salt to chlorine and the chlorine returns to salt as it is consumed, so the cycle is closed. What removes salt from a pool is water leaving it — backwashing, splash-out, rain overflow — which is the same mechanism that lowers stabiliser.
Last reviewed 21 September 2026