CYA from 180 to 0? How?

[lmbr]

Hi everyone, I've got a weird problem here and I'm not sure if I should trust my test results.

I inherited a pool a year ago and used a Taylor test kit to get a CYA reading of ~180. Obviously not good, but I put off draining the pool at the time and instead only switched from stabilized to unstabilized chlorine. Now, a year later, I've tested the CYA again and got a reading of 0.

Should I trust this result and now try to boost the CYA? I'm not sure how to explain that drop, given that CYA doesn't evaporate and breaks down slowly.

Any help is appreciated. Thanks!

 

[PoolStored]

Welcome to TFP!!!

It is possible that you are 0, particularly if it has been a year, and your pool temperatures are high (80+)...

How old are your reagents (what is the date on the reagents, including the CYA reagent)?
Post a full set of results.
Would be good to get a picture of the CYA test in the tube to confirm...

 

[mknauss]

Welcome to the forum.
Did it rain this winter? Did the pool overflow or did you have to drain any water this winter? Your CYA will degrade some as Pool stated.
I would do an ammonia test before adding any CYA. See Ammonia - Further Reading

 

[woodyp]

Does your pool have an autofill?

 

[lmbr]

Welcome to TFP!!!

It is possible that you are 0, particularly if it has been a year, and your pool temperatures are high (80+)...

How old are your reagents (what is the date on the reagents, including the CYA reagent)?
Post a full set of results.
Would be good to get a picture of the CYA test in the tube to confirm...

Thanks for responding!

The water temperature on average is probably 10-20 degrees below 80. The date on the CYA reagent is 6/23, so expiring soon but not yet. I already threw out the CYA test in tube -- I can redo the test (I have enough reagent for probably only one more), but the tube was almost totally clear the first time.

By full results, do you mean for chlorine, ph, etc.?

 

[PoolStored]

By full results, do you mean for chlorine, ph, etc.?

Yes.

If the CYA tube was clear, no need to do the test again, save the reagent. CYA reagent is fairly stable.

 

[lmbr]

Welcome to the forum.
Did it rain this winter? Did the pool overflow or did you have to drain any water this winter? Your CYA will degrade some as Pool stated.
I would do an ammonia test before adding any CYA. See Ammonia - Further Reading

It did rain, but I never had to drain water. I'll go forward with that ammonia test before trying to increase the CYA. Thanks!

 

[lmbr]

Does your pool have an autofill?

Yes. But I figured that the CYA would stick around regardless since it doesn't evaporate.

 

[mknauss]

You must have an overflow if you did not have to drain water at all.

Unless you live in the desert.

 

[lmbr]

You must have an overflow if you did not have to drain water at all.

Unless you live in the desert.

It's possible that I'm misunderstanding something, but I thought the main thing that's been draining water from the pool is evaporation. I get probably ~10 inches of rain in a year and figured that evaporation was what covered for that.

 

[mknauss]

If you live where I live, yes. But the coastal areas of California got quite a bit of rain in a short time this winter. As I said, if you live in Barstow, not an issue. If you live in Ventura, hard to believe you did not get enough rain to cause overflow. I guess it could be, but everyone else on the forum from coastal California had to drain water pretty frequently.

 

[PoolStored]

It's possible that I'm misunderstanding something, but I thought the main thing that's been draining water from the pool is evaporation. I get probably ~10 inches of rain in a year and figured that evaporation was what covered for that.

Maybe update your information to include your city?

 

[getreal720]

I typically keep my CYA right at 30 PPM.
I close my pool right around the time the leaves start falling here in PA. I don't open it until around the start of June as the nights here just get too cold, even with a solar cover on it, to have it be very swimmable before then. This will be my 7th season with this pool now and 7th total for me maintaining a pool. It's an above ground pool, vinyl liner, sand filter... about 13,000 gallons of water.
Every June when I open the pool, I noticed that my CYA is usually at 0 and I have to add about a pound to a pound and a half to get it back to 30PPM IIRC. Not sure why but my CYA seems fully expire over each winter. No significant water loss. I normally add "maybe" 10% to 15% of the volume of the pool water back at the start of each season as the weight of snow and ice on the cover of the pool will force water out. So yeah, that factors in... but not 30 PPM to basically nothing. I also calculate how much CYA it takes to get back to the target of 30PPM given my pool water volume, so that means I'm usually bang on fresh out of CYA at the start of each season.