How long before measuring CYA after drain & fill

[SunnyOptimism]

For CYA test, what is the recommended amount of mixing time after a partial drain and fill. In my case, I drained approximately 900 gallons on a 17000 gal pool (~ 5%) and refilled with city water.

I tested the following day but the total run time of the pumps during that period before testing probably was less than 8 hours. I went from a previous reading of 60ppm to now reading 40ppm.

So either my previous reading was too high or my current reading too low. There's been a little rain water here and there but nothing that significantly altered the pool volume. Water is crystal clear and sparkly.


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[duraleigh]

Since the CYA was already "mixed" in your pool, there is no mixing time...the results should be essentially instantaneous.

If you drain 900 gallons from a 17k pool, you should experience a 5% reduction in CYA....so down to 57% instead of 60....not much.

I can't tell you which test was wrong so you might just split the difference and call your CYA 50 ppm.....that should work.

The pump run time is, essentially, not relevant. 30-60 minutes should be plenty to get everything blended.

 

[SunnyOptimism]

Yeah, I'm going to retest again tomorrow. I should probably buy the 50ppm CYA standard from TFTestKits to calibrate my eyeball to what the black dot disappearance should look like. I definitely tried hard to make sure I used similar lighting conditions. Perhaps I have Superman-like X-ray vision

I have a bucket of 1" spa trichlor tablets so if I felt like the CYA was truly low, I can always try to bump it a bit with those since they're smaller than a big 'ol 3" puck.

Thanks. I'm not going to lose too much sleep over this...just needed to do a sanity check...

Insane neurotic pool owner, CHECK!


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