Sorry you’ve had issues. But I’ve used that kit for years and it’s spot on accurate. I’ve even measured homemade standard solutions and it comes well within testing error limit. The chemistry behind the test is very simple so there’s not much that can go wrong. Perhaps there’s something in your water interfering but it’s hard to say. I’m not a huge fan of Hayward cell salinity measuring methodology as it uses the cell itself to act as conductivity probe. That can be fraught with difficulty as it assumes all cells are the same and infers EC based on cell electrical parameters. Not a good assumption to make. That said, none of the manufacturers do a very good job on salinity measurement so you have to take what you get.
Meters are not foolproof. Even if they are calibrated against a standard, it still isn’t going to give accurate results because pool water has lots of dissolved ions in it. That is going to produce an offset in the measurement that you can’t account for easily. So, in the end, it’s no better than using the SWG because you really have no way of knowing how the EC value compares to the true chloride content of the water. The K-1766 measures chloride content exactly.
Hope you get it sorted out. And, on the bright side, you have a spare cell. Or, maybe you can come up with a creative way to run both cells in parallel and then halve your pump run time.
I understand your point about the chemistry using the K1766 vs the reliability of meters.
So where does this leave an average pool owner like me when trying to figure out if a new cell is needed?
I followed the standard advice here using the K1766 results compared to the old T15 cell salt readings, which lead to buying a new cell. But when the new cell resulted in the same results as the old cell, I had the cells tested (both passed no problem). I had the store that tested the cells also check the salt level (they used some kind of electronic meter) and their result was in close agreement with what my SWCG is reporting.
So what do I do going forward? Just feed the SWCG when it reads low as long as it’s producing adequate FC, and just have the cell tested if I suspect it’s dying? Worse case, when the existing cell proves dead, this may result in high salt warning with a new cell, requiring some water replacement/rebalancing a few chems.
If I just rely on the K1766 to tell me when to replace a cell, then I risk the situation buying an expensive new cell unnecessarily.
You mentioned something in the water possibly causing an interference. Anything in this list stand out as a possible source of interference?
68% Cal Hypo (LC was in short supply at opening, I don’t normally add calcium, so CA level is usually below 100)
10% liquid chlorine (normally use at opening, and once in a great while to bump up FC if needed)
Water softener salt (no additives)
100% CYA (70-80ppm)
Borax (used to raise pH at opening)
Boric Acid (50ppm)
Washing Soda (used at opening to raise pH and TA)
Jack’s Magic Purple Stuff (2qts at opening, approx 12oz weekly for iron stain control. Using a Taylor drop test recently, phosphate measured 2000ppb)
My apologies to the OP for sidetracking this thread. Perhaps this discussion should be continued in my SWCG thread (Moderator, please advise)?