Salt Generators

I have a "Clormatic" brand generator, and after 4 years it failed. The cell was warranted for 2 years, and prorated for an additional 3 years.
I'm convinced that ignorance on my part contributed to the failure.
I was unaware that elevated levels of "Nitrate" and "Phosphate" in the pool water significantly reduced the efficiency and hence the chlorine output of the cell.
I purchased NITRATE test strips from "Hach" company , catalog #27454-25, and "PHOS-Free" from the local pool store. This solved my problem after I dumped and refilled a third of the pool.
You need to be aware that with Nitrate and Phosphate in the water, the 26volts DC imposed on the cell is not producing the proper quantity of chlorine,and is reducing the life expecting of the cell.
Use fertilizer with caution around your pool.

Hmmm. sounds like TDS might be at play here. High TDS will increase the electrical conductivity of the water. Ideally the TDS should be almost the same as the salt level from what I have been able to ascertain. Not familair with the SWG you mention so I don't know if it has a readout on it of salt level which is usually a conductivity reading of the water but the introduction of nitrates and phospates from fertilizer runoff would certainly raise your TDS and that would produce a correct reading with a much lower actual salt concentration in the water.

Maybe I'm splitting hairs but it's not about the cell-phosphate relationship. High phosphates will eat up your chlorine in the pool. If the phosphates are high enough the cell won't be able to keep up and it's time for phosphate removal, either with No-Phos or Alum. My phosphates build up >3000 ppm within 3 years from fill water and even with supplemental bleach, residual chlorine disappears quick at that value. Phosphates won't reduce the life of the cell unless you increase output to compensate for them.
Hope this helps, Tony