Reliability of CYA Readings in a Pool with Excessive Algae

[mcolflesh]

Hello,

I am in the process of doing partial drains and refills on my pool with high CYA (between 90-100). This is a green swamp I am preparing to SLAM. Since I am waiting for my pool to refill, I was boning up on how to be best prepared to SLAM. I read a few things here and there about the unreliability of the CYA test when algae is high. Also, there seems to be some debate about the reliability of the CYA test when the water temperature you're testing is under 70 degrees F.

So, I'm hoping to retest for CYA in the next day or two after my water level is back up to operational level. Am I likely getting unreliable test results due to excessive amounts of algae. I read on on pool blog that I should pour my water sample through a coffee filter prior to running the CYA test if I have excessive algae. Any thoughts or feedback would be appreciated. Thank you!

 

[JoyfulNoise]

Temperature doesn't matter. Many of us have confirmed that the test reads equally well in cold water (temp <68F) or warm water. If the water were super-cold, like near freezing, the reaction that forms the cloudiness might be a little slower but it would still happen.

As for algae, it really depends. Most of the time, when people pull a water sample from a green swamp, the water sample is still mostly clear since it's really only in large volumes do you see the algae as a opaque green color. If the water sample itself were very cloudy, you might get a false-high reading but it probably wouldn't be too far off from your actual value AND it would error on the high side which means you'd probably add a bit more chlorine to the pool during the initial phases of the SLAM then you would otherwise. This would not necessarily be a bad thing and the water would eventually clear to the point where you could do another more accurate CYA test.

You can always take some of the water sample and just add it to the view tube. If you can fill the view tube to the top and still see the black dot, then the presence of the algae will have little impact on the reading.