Drastic Change in CYA & TA

[momtaps]

In the four years that we have had our pool, chlorine and acid is about all we ever need to add. Our CYA and TA levels have always been stable. Now, without any rain, only adding about 2" of water to the pool, and running the heat pump the last couple of weeks, our CYA has dropped from 40 to not even registering (I checked it several times with a brand new test kit), and our TA went from 120 to 80. I used PoolMath and added what needed to be added, but any suggestions as to what could have possibly happened?

FC5
TA 80
CH540 (it's always been high and we've never had any signs of scale)
ph 7.8
CYA Not even slightly cloudy in the tube (I entered 0 for CYA in PoolMath)

Thanks for your help!
Kristi

 

[pwrstrk]

My I ask what test kit you using and are you just opening it up for the season ? CYA can sometimes disappear over the winter.
Can you also give a CC test result ?

 

[momtaps]

It's been open since mid March. The CYA was at 40. I just added chemicals, so I will check the CC tomorrow and post results. I use the TF100 test kit. I tested with last years kit and again with the new replacement kit I just got in - same results so I don't think it is a problem with the test kit.

 

[duraleigh]

Re: Drastic Change in CYA & TA

Kristi,

I think the TA drop is reasonably close to normal......assuming it's been a couple of weeks or more since the last test.

The CYA loss is pretty inexplicable for now, As the forum grows older (7 years now, I think), we gather more information about our pools.

We have had other reports of CYA disappearing that can be attributed to an over-the-winter condition but yours seems not to be the case. No definitive answer for now but glad you caught it. Please put your City and State in your profile (it's in "settings"). Climactic info is helpful.