I recently had my salt water pool water tested at my local pool supply store. The readout lists Total Alkalinity (Input) at 121 ppm and Total Alkalinity (Adjusted) at 95 ppm. The store clerk could not explain the Adjusted number but told me not to worry, my Alkalinity number is "OK". All of the pool test kits, Pool Exact EZ digital Photometer reader as well as online blog and forum advise only talks about 1 Total Alkalinity measure. What is Adjusted Total Alkalinity and should I use that number or the more common Total Alkalinity (Input) number?
Total Alkalinity (Input) or Total Alkalinity (Adjusted)
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- Last Post 20 August 2021
Adjusted total alkalinity is calculated by subtracting 1/3 of the CYA level from the total alkalinity reading. As an example, if the TA reading is 120 ppm and the cya reading is 75ppm, the adjusted TA would be 95 ppm.
Since the acceptable range for TA in a salt water pool is 80-120 ppm, you can see that the adjusted TA wouldn't result in needing to adjust the TA level. Adjusted TA is a pool store thing. Nobody uses adjusted TA when calculating water balance. I don't know of a single test kit out there that has an adjusted total alkalinity test.
If you keep the proper amount of chlorine for the CYA level and keep the TA within the recommended range, you shouldn't have any issues.
Adjusted total alkalinity is also part of calculating the CSI, but that's another topic.