Lately we've been seeing a number of our pools with SWGs with low salt, but everything shows they are working fine. Most of the pools in question are using EcoMatic SWGs. The Ecomatics read 100 when salt levels are where they should be, or at least thats how they are supposed to work. When salt levels drop below about 2500ppm, the number will drop below 100. There isn't an exact conversion for what the numbers mean as far as I know, but usually you can tell when it says 96 it only needs a little bit of salt, and if it reads 75 it needs more.
The pools I've been seeing will read 100 as if salt levels are fine. When I test the salt, I get all kinds of readings, which are all below the operating range. I've seen some as low as 1500ppm, yet the display still says everything is fine. I also see that the system is generating, based on the cloudiness at the cell. So up until now I have been assuming that if the pool is generating, it should be fine. I'm wondering if that is correct, or if a pool generating with a salt concentration of 3000ppm is working more efficiently, or generating more chlorine than a pool with a salt concentration of 1500ppm.
These systems are supposed to shut themselves down when salt levels are too low to operate. Will running with low salt damage the cell? Why might this be happening? Why aren't the systems picking up on the low salt level? Any thoughts?