I have never tested my fill water for salt; perhaps I should. Prior to installing a SWG we used cal-hypo and bleach. I know that bleach adds salt to the pool water. Chem geek posted the following:
"ALL sources of chlorine add salt because when the chlorine gets used up / consumed it results in salt. For every 10 ppm FC added by ANY source of chlorine, it will result in 8.2 ppm salt from the consumed chlorine that turns into chloride salt. With bleach, chlorinating liquid, and lithium hypochlorite, there is an additional 8.2 ppm salt upon addition so the net total result is 16.5 ppm. However, even at 3 ppm FC per day chlorine usage for 6 months this is around 890 ppm added salt if you had no water dilution." See
bleach-leaves-to-much-salt-in-the-pool-t25232.html
You will save time, money, and frustration if you do all the water testing yourself. Pool stores use water testing methods that are fast so they can quickly sell products and move on to the next customer. If your water quality is beginning to show problems waiting a day or two until you have time to run to the pool store to have the water tested will only make the problem worse and more expensive to resolve.
For example, if you go to the pool calculator,
http://www.poolcalculator.com/ , and see the CSI, you will see that proper pH control is important to preventing scaling of your SWG plates.
I have not relied on pool store testing for three years and our pool has improved in feel and appearance.