CYA Drops Drastically

Mendy48

Bronze Supporter
Apr 27, 2018
902
Midland, MI
So I know I’ve been very lackadaisical when it comes to my pools CYA. It jumped from 50 (July 28th) to <20 (September 21st). We had a very hot summer, but it just didn’t dawn on me to keep an eye out on my CYA. I don’t think we’ll be swimming anytime soon, as the weather is getting pretty cold now. So I dumped a bunch of 1” Chlorinating Tablets in my Chlorinator (80onzes). I really don’t know why I did that. I was irritated and didn’t have enough CYA liquid to use.

Anyhow!!!! Is this normal? Is it possible to lose so much CYA in two months?
 

Newdude

Well-known member
Jun 16, 2019
4,566
NY
There were definitely other people who saw large unexplainable drops this year. Pretty much this whole year has been unexplainable. Across the board. A drop of 2-5 per month is expected. Maybe double that to 4-10 if you got heavy rains or extra sun like some areas did. 15 per month is just alot period. But then again, Its 2020. Lol
 
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Mendy48

Bronze Supporter
Apr 27, 2018
902
Midland, MI
Yeah... I’ve never seen anything like this before. It’s just very strange. I was expecting to see a CYA of 30, but not <20. Very strange 2020 year we’re in. 🤔
 

JamesW

TFP Expert
Mar 2, 2011
21,075
So I dumped a bunch of 1” Chlorinating Tablets in my Chlorinator (80onzes).
That was a bad idea. You should remove the tabs so that the fc doesn't get too high.

You can't just close the valve because the tabs are already wet and they will create a dangerous situation.
 

JamesW

TFP Expert
Mar 2, 2011
21,075
Yes.

You need to let them dry out. It's a bad situation because the tabs are wet and they are going to smell strong until they dry out. Make sure that they are not where pets or kids can get to them
 

Mendy48

Bronze Supporter
Apr 27, 2018
902
Midland, MI
So I go to the pool store to get liquid stabilizer. I need to up my CYA because I think it’s actually at zero. Though I can’t really measure under 20. But she then tells me that I don’t need my CYA to be high above zero since I’ll be closing it in four weeks. I looked at her and said well I need it anyway I didn’t feel like arguing. But that’s my experience with the pool store yesterday. 🤦🏽‍♀️
 
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Newdude

Well-known member
Jun 16, 2019
4,566
NY
For it to be ammonia it has to be zero. And zero again soon after you add, no matter how much. Supposedly it just eats up the CYA and the FC.
 

BowserB

Silver Supporter
Jul 29, 2018
363
Katy, Texas
Mendy, I've had CYA drops in spring and then again later in the summer. It's really hot down here in Houston, and the UV is murder. When the CYA drops, I first make a new batch of test solution to verify--and a couple times I've even taken a sample to Leslies for a second opinion. I normally chlorinate with liquid chlorine. If CYA gets low, I put tabs in a floater in the spa, which spills over into the pool. I put it in the spa just so it won't drift to a skimmer and cause excessive chlorine levels in the pump and heater. I check the CYA every couple days until it's back to normal. Then I store the floater outside under a bucket in a corner where the fumes will only bother rats and mice! Of course, I check the chlorine every day, as the floater usually doesn't raise it high enough on its own, especially with low CYA, and supplement with liquid chlorine. Sounds tedius, but it's only two or three times a year--or right now, since we've just had nearly 12 inches of rain in the last several days.
 
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Mendy48

Bronze Supporter
Apr 27, 2018
902
Midland, MI
So, I don't have ammonia at all. Doesn't FC have to be 0 for there to be a chance of Ammonia. I did the test anyhow, and it passed. Tested my pool's FC at 7, added LC to get 10ppm and tested again after 30 minutes. Pool FC is not 10ppm.

My CYA is just really really really low. If not "0". We've had a very very very HOT summer. I didn't check my CYA for 2 months during those summer months in Michigan. I checked my CYA again today, and the water is clear below 20...very very clear. So I added enough liquid CYA today. (see my PoolMath Log). I'm hoping for a better CYA result in 24 hours.
 

mguzzy

Gold Supporter
Jul 8, 2015
2,386
OV, CA
OK.. perfect I just wanted to make sure there wasn't something else going on in the soup bowl...

Sounds like you know the CYA dance wait awhile and we will see how it responds.
 
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simonoaks

LifeTime Supporter
May 28, 2015
296
Juno Beach , Florida
So, I don't have ammonia at all. Doesn't FC have to be 0 for there to be a chance of Ammonia. I did the test anyhow, and it passed. Tested my pool's FC at 7, added LC to get 10ppm and tested again after 30 minutes. Pool FC is not 10ppm.

My CYA is just really really really low. If not "0". We've had a very very very HOT summer. I didn't check my CYA for 2 months during those summer months in Michigan. I checked my CYA again today, and the water is clear below 20...very very clear. So I added enough liquid CYA today. (see my PoolMath Log). I'm hoping for a better CYA result in 24 hours.
As a side note, I always run an overnight test before adding CYA. I have been caught out before, where there was algae I did not know about , and then BANG ! I detect it through loss of FC and then have to SLAM at 80-90 CYA levels- which obviously means way more bleach, and the issue that you cannot test accurately enough for an overnight test , so have to let it drop to a testable level instead of holding at SLAM level.

Anyway, just a thought , just in case you do have to SLAM , it will be way quicker and easier at under 20 CYA!
 

thefloatqueen

Bronze Supporter
Dec 24, 2018
665
Columbus, OH
You’re not alone!! Last summer, my CYA stayed at 40 or 50 from the first time I added stabilizer when I first got my pool all the way until closing the first week of November — even with rain, adding fill water, splash out, hot temperatures, everything!

This summer, I’ve had to add stabilizer (via sock method) over 5 times just to barely keep it at 40. And that is NOT including the few times I added dichlor or a couple trichlor tablets in my 3” floater to try to slowly bump the CYA up (I strictly use liquid chlorine 99.5% of the time). I even increased it to 50 at one point since I knew it would end up dropping again. Very strange! Glad to know it’s not just me!
 
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DAB942

Gold Supporter
Nov 13, 2017
494
Space Coast, FL
So I know I’ve been very lackadaisical when it comes to my pools CYA. It jumped from 50 (July 28th) to <20 (September 21st). We had a very hot summer, but it just didn’t dawn on me to keep an eye out on my CYA. I don’t think we’ll be swimming anytime soon, as the weather is getting pretty cold now. So I dumped a bunch of 1” Chlorinating Tablets in my Chlorinator (80onzes). I really don’t know why I did that. I was irritated and didn’t have enough CYA liquid to use.

Anyhow!!!! Is this normal? Is it possible to lose so much CYA in two months?
I just went through the same thing. I put ten pounds of CYA in my pool and it did nothing. It was a roaster this Summer and rained like crazy too. I just added ten pounds over the last couple of weeks and mine went from 20 to 70. I'm starting to think that store sold me ten pounds of dextrose.
 
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