A very peculiar question, kind sir
I supposed one can start by allowing his pool water to evaporate in the blazing summer heat in order to separate the solute (salt) from the solvent (water). After the separation, the obtained mass of salt can be measured on a scale in order to determine the concentration of salt that is present within thy swimming pool. This technique is the most classic of all, and is also the most expedient way to extract salt from water.
