Total Alkalinity and Adjusted Total Alkalinity

[cheshamjim]

The test printouts from two different pool stores I've used show a Total Alkalinity catergory and an Adjusted Total Alkalinity category. Sometimes the adjusted is lower and sometimes the two numbers match. This over the span of 15 tests since May 8.

What's this all about?

-Jim

[cwstnsko]

The only adjustment to TA that I'm familiar with is to subtract 1/3 of the CYA value from the test results. This is sometimes referred to as CYA corrected TA. Usually this "correction" comes into play when discussing the Saturation Index, and even then it is debated as to whether the correction is appropriate. This site usually doesn't put a lot of merit in the saturation index unless you're running a heater. I usually keep my CYA low enough that the correction is not significant one way or the other.

[waterbear]

When you add CYA (stabilizer) to a pool it forms a secondary buffer system of cyanuric acid/cyanurates in the water. This will test as part of the Total Alkalinity (cabonic acid/bicarbonate/carbonate buffer system) on the test but is not really part of it. A mathematical correction is applied determined by the pH and CYA level at the time of the test and then subtracted from the TA to get the ajusted TA. The jury is still out on the value of this correction although Taylor Technologies (manufacturer of one of the better lines of water testing kits) does endorse it. IF the pH is 7.4 then this correction is approx. 1/3 the CYA level.