Please read AQUATIP 1 first. Your salt system requires a constant level of salt in the pool water. My salt system operates best around 3,200 ppm (parts per million of salt in the pool water) although some salt systems operate efficiently at a higher or lower ppm. Salt ppm levels do change; usually they go down not up. Common reasons are rain, backwashing, and splashing pool water out of the pool. In areas with large rainfall amounts, salt levels can drop sharply in a hurry. Testing your pool salt level is easy.
Most salt systems have their own readout for salt levels. I suggest a second or third method as a backup. As always, your Professional Pool Supply Store will help you with a salt ppm analysis. The top picture on the left is using a digital salt tester. They are a bit pricey and require following some detailed instructions however they are very precise and for that reason used by many Pool Service Technicians. The drip method is my personal favorite. It uses a few drops of silver nitrate and a chromate indicator for a quick color change indication of your salt level. It is fast, easy to use and accurate. Test strips are also very popular and a quick way to obtain a salt level in your pool.