I have the Pentair Intellichlor SWG ( less than a year old). I recently had my 17,000 Gallon pool levels at the required level (3600). The light came on later with low salt reading. I tested and it was reading 2400. I added salt, got the level back up to 3600 and it's now saying low salt again and reading 2400 and it's only been a couple of weeks if that. We are in VA; temps in the 90's and we did just got six inches of rain. My question is it normal for the numbers to drop that much after six inches of rain and have to add 2-3 bags of salt again?