Re: Salt Water Pool Conversion
a couple of thoughts:
Does your pool have an autofill and an overflow? A malfunctioning autofill can cause what you describe.
salt levels move with down CYA levels since they are both only lost by splashout, backwashing, and leaks.. Have you checked CYA to see if it is decreasing over time?
If you are using salt test strips (AquaChek) they take a full 10 minutes to develop. Most pool stores do not wait that long and the instructions on the bottle are not that clear (I got the 10 minute time from a tech note on the Hach/AquaChek website if anyone is interested in my source). If you do not wait long enough the strip, which is really a titrator, will read low.
As far as the low salt light on your unit...Your unit is reading conductivity, which is affected by more than just the level of salt in the water. Temperature, the age of the cell, the cleanliness of the cell, TDS, etc. all come into play. Chemical salt tests are tests for chloride ions (whether they are strips or titrations aka drop count tests). The chloride ion level in the water does not always correlate to the conductivity of the water. As cells age they will act like the salt is low even when it is not. Handheld electronic salt meters that some poolstores use also work by measuring conductivity. They range from very accurate if they are kept calibrated to so bad that you can get a better idea by tasting how salty the water is. My experience has been that MyronL and Oakton/Eutech meters (often rebranded as Goldline) are dependable if kept calibrated but if the store is using someting else I would not trust the results.
Finally, if you and the pool store are all testing with strips I would suspect a bad batch. Hach/AquaChek recently had a bad batch of strips that they documented on their website.
Retired pool store and commercial pool maintenance guy.
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