Well this morning, the salt reading was back up to 3000 PPM, though instant salt is showing 2700 (it was 2900 to 3000 with the old cell). I just realized that I do have a salt test after all. It came with my PS234 kit but I never used it before. The drop test read 3400 PPM, which seems to be in the ball park of the 3000 that the Aqua Rite display is now showing. So now I'm thinking it's probably just a minor variation between what the old cell and new cell is reading, and my old unit was fine all along. So I'll put the old one back on and consider the new one a spare!

Is there a shelf life for either chemical in the salt test (potassium chromate & silver nitrate)? The test kit is 7 years old. Neither reagent bottle was ever opened before today, if that makes a difference.

Thanks,
Steve