Re: Adjusted? Total ALk?
First I want to say that their numbers are bogus even for the ajusted alk!
The level of cya in the water will test as part of the total alkalinity even though it is not part of the carbonate/bicarbonate buffer system we are testing when we test alkalinity. There is a mathamatical correction that is applied based on pH and CYA level to be subtracted from the ALK to get the 'adjusted alk'. This supposedly more truely represents the amount of carbonate/bicarbonate in the water. The value of this adjustment seems to be the topic of some debate. Taylor Technoligies sees merit in it. Your pool guy was right in saying that if you had no CYA the ALK and Adjusted ALK would be the same. Personally, I don't think it matter much unless the CYA levels are above about 60 ppm since below that it really doesn't change th ALK reading very much. If you want to get a 'quick and dirty' adjusted alk reading then subtract 1/3 of your CYA reading from the ALK if you pH is 7.4 or above and 1/4 of your CYA if the pH is 7.0-7.2. You can see that if the CYA is above 60 ppm at normal ph (7.4-7.6) this means that it can affect the ALK reading by 20 ppm or greater... If you CYA is around 30 it really only changes it by about 10 ppm which is nothing to lose sleep over!
Hope this explains it.
The reason I say the Alex readings are bogus is that they are done with test strips and a reader. They have your CYA closer to 60 ppm than 30 ppm to get that much of a difference in the ALK and the adjusted ALK. I would trust the ALK reading from your drop baed kit. Your adjusted ALK is in the neighborhool of 110 ppm....perfect!
Retired pool store and commercial pool maintenance guy.
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