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I place some water in the "cup" at the top and push a button and hold.HTM
The strips seem to work OK but I find the range isn't very good. Â I think there's a marker on the strip for 1500 and the next one is for 3000. Â If you are looking to make sure it's under 2000 it's hard to judge with the way the strips are setup.
I would not recommend using a spa with TDS over 1500. 3000 is useless as well as the pool should be drained at 2500.HTM