Karin & Others,

The 60 - 80 ppm CYA recommended by the SWCG manufacturers is because the cell instantaneously creates a high concentration of chlorine, and kills the chloramines as well.

Without the high CYA, the chlorine would be used up rapidly before it gets into the body of the pool.

With my SWCG, a 50 - 60 ppm CYA level appears to work fine. So 50 ppm you are using is in the ballpark.

Regarding the staining, it could well come from your fill water, but others with more experience can help you. Have you tried to brush this stain? To my knowledge CYA does not stain, otherwise we would be using something else.

Your water chemistry apart from the CYA is also in the ballpark, and I can well understand your frustration with 4 pool stores giving you different readings, so I take them with a pinch of salt (pun intended) They do not know how to be consistent. Once you do it yourself the same identical way each time, you will be less frustrated

mas985, I would use option #2, based on what I said at the beginning. The cell should produce the chlorine regardless, and if not you can always aise the output. A bit of trial & error. I have not heard of CYA dissolving plaster pools. That's a new one to me. Will have to investigate.

Hope this helps.

Pat