Hey Woody.

The reason I asked about the test method was to see if you were relying on the unit to tell you the salinity. Since you're using an electronic tester, that's out (as is the temp. skewing your results). I'll assume that the tester has been calibrated correctly.

With you having an autofill, I'd say you are loosing a lot of water daily Since the board doesn't want to enlarge the trough, can you put up a barrier to minimize the loss? Another possibility is to somehow deflect the water coming off the ledge so that most of it will stay in the collection trough (though that's likely to be less aesthetically pleasing to the pool users)

Please let us know how things turn out & of course, ask any other questions you have.