In a vinyl liner pool, the calcium hardness is not that important. However, I would recommend that you have the water tested and compared to the saturation index, which determines if the overall water chemistry is balanced, corrosive, or scale forming. It is the last condition that can cause problems with the swg.
The good thing is that once you've balanced your water to the saturation index, the swg should not do anything to cause it to come out of balance and should ensure proper operation of your salt system.
So, having said that, if you can provide a complete water chemistry test, we can help determine if you're balanced, or what chems are needed to balance your pool.
Free Chlorine
Total Chlorine
pH
Total Alkalinity
Calcium Hardness
Water Temperature
Cyanuric Acid
Salinity.