Cya fluctuation

[grottoguy]

We use the TFP test kit that this cite recommends and my wife does the pool testing for consistency. Our CYA seems to fluctuate a lot. Sometimes its 50, then it could be 65 or if I add some stabilizer, it could be 70. But then it drops. We bought the test CYA solution that I saw mentioned on this cite (where you pour in the test solution instead of the actual pool water) and everytime she uses it, she gets 50 (which is what she is supposed to get). Thus, I think her testing of the CYA is accurate.

My question is should CYA be fluctuating with perhaps evaporation or PH movement? Our new Pool was just filled in June and PH does rise frequently, if that affects CYA.

Thanks

 

[YippeeSkippy]

Hmmmm... new pool, with autofill. Any chance of their being a leak you're not aware of which is causing it to be refilled (diluted) continuously?
Have you had enormous amounts of rain that have caused the pool to require draining down at times?

pH does not affect CYA, although evaporation does because you refill with fresh CYA-free water.

 

[JoyfulNoise]

CYA only changes with dilution - drain&fill or leak.

The CYA test also has a stated accuracy of +/-15ppm. It can also vary a lot with lighting conditions. It is good that only one of you is doing it regularly.


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[grottoguy]

There is no chance of a leak because my autofill has not been on. I haven't needed it till now and they need to fix it anyway so I have had it turned off at my hose bib so no water could have been going to the pool. We also have never drained the pool for any reason. I'll test gain today and see what we get. Thanks everyone.

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The only thing I can think of is that we were losing water to evaporation and then getting more water from rain

 

[JoyfulNoise]

There is no chance of a leak because my autofill has not been on. I haven't needed it till now and they need to fix it anyway so I have had it turned off at my hose bib so no water could have been going to the pool. We also have never drained the pool for any reason. I'll test gain today and see what we get. Thanks everyone.

- - - Updated - - -

The only thing I can think of is that we were losing water to evaporation and then getting more water from rain

Evaporation will not affect CYA. If the rain water simply replaced evaporated water then there's no change in CYA. If the rain water overflows the pool or if it filled it up and you then drained it, that could change CYA. Typically speaking, unless your pool volume is fairly small, a 1"-2" change in water level is usually only a few % change in volume. For example, 3" of water level change in my pool is only a ~5% change in total volume. that would be unnoticeable on a CYA test.


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