Wondering if CYA drops more rapidly in really hot climates

Woodberg

Well-known member
I'm beginning to wonder if the CYA level is somehow dropping more rapidly in pools in really hot climates like Texas. A friend of mine has been using pucks to chlorinate his pool for years. He does the standard weekly shocking treatment with some pool store product. Recently he had a very bad algae breakout and the pool turned green in a couple of days. All he evers measures is Chlorine level and PH. He didn't even know what CYA is. I figured I would use the opportunity to help educate him on the effects of high CYA. When I tested his pool, his CYA level was 60. This is a pool that is open year around with pucks used for sanitizing 24-7.

In my own pool in Houston, I use bleach primarily but also use pucks when I'm out of town. This spring my CYA level was low and I used a lot of pucks while my CYA level rose. However, it didn't rise nearly as fast as the Pool Calculator said. I bet I added 30 pucks over the course of the spring and my CYA rose about 20PPM.

Is there any information of other potential ways CYA could drop?
 

busbeepbeep

Member
Jul 5, 2007
24
New Orleans, LA
Re: My CYA seems to be disappearing

Woodberg, my pool is really hot Louisiana is having similar problems. I've added enough stabilizer to measure about 60ppm in my pool (8lbs), but still only seeing 20-25 ppm on my test. (Tried both TF-100 and HTH 6 way)
 

JasonLion

TFP Expert
Platinum Supporter
LifeTime Supporter
May 7, 2007
37,880
Silver Spring, MD
Re: My CYA seems to be disappearing

It has been a couple of years, but there have been problems in the past where CYA from the store didn't actually contain any CYA. On other occasions the CYA was actually 50% CYA instead of 100% CYA.

CYA does break down, but it does so really really slowly. Normally splash out and other forms of water replacement are far more significant.
 

Woodberg

Well-known member
All of my other numbers are stable. In my case, I would have just thought that my CYA would have increased more dramatically from using the number of pucks I used. In my friends pool, he is exclusively using Tri-Chlor pucks and yet his CYA was only 60. He does backwash occaisionally but not enough to to keep the CYA that low.

In my case, I have a cartridge filter. I have some splash out from the kids swimming but most of my water loss is evaporation which shouldn't reduce the CYA.
 

chem geek

TFP Expert
LifeTime Supporter
Mar 28, 2007
12,082
San Rafael, CA USA
Could dilution be occurring from rain overflow? According to this link you seem to get rain all year long in every month for a total of around 48" (4 feet) per year. If the rain is just filling up what is evaporated, then that shouldn't dilute the water, but if the water overflows from the pool, then dilution would occur.

The oxidation of CYA by chlorine is probably dependent on the temperature of the pool, but we keep our pool warm at around 88ºF and such oxidation seems pretty slow at around 2 ppm CYA per month, approximately (but our pool is covered during the day except for 1-2 hours). Even in hot spas (104ºF), people doing measurements found a loss of around 5 ppm CYA per month. Now it's possible that this oxidation is catalyzed by some sort of other chemicals or metals or occurs more rapidly when there is more sunlight, but that's just speculation at this point. Also, any loss of CYA through this mechanism would likely have a much higher chlorine demand since every drop of 10 ppm CYA would use up around 25 ppm of chlorine. It is known that the oxidation of CYA by chlorine does occur much faster at higher pH so has your pH been higher than normal, say at 7.8 or higher the entire time?
 

anonapersona

TFP Expert
LifeTime Supporter
Nov 5, 2008
2,598
In my pool the CYA is dropping. I have an abnormal amount of water loss in this 95-100 degree weather due to the waterfall. I don't run it all the time, due to evaporation and the big pump that runs it, but even running it 3x/day to keep the pools chlorinated means that some water evaporates or soaks through the rocks to be lost. And I overflowed once or twice - doh! And then heard the pump acting funny, went over there to find water gushing out of the top of the not totally screwed on automatic chlorinator -doh! So in addition to 4" of rain this month, most of which overflowed, I've added an extra 3 or 4" myself that overflowed.
 

ajones02

Platinum Supporter
LifeTime Supporter
Feb 4, 2010
118
Keller, Texas
woodberg, i've had some issue's as well with CYA disappearing. i did the bucket test and i do not have a leak. i do know i add water every 2-3 days and there is some splash out so that could be part of the problem as well. per chem geek suggestion, just chalk it up to a mystery, add some stabilizer and move on from there. i typically test my CYA every 2 weeks now just to keep an eye on it.
 

dd50

Well-known member
May 31, 2008
112
florida
I had the same problem when I purchased the product from Lowe's and that was before the rainy season. I then purchased from the pool store and so far so good and it has been raining every day.
 

Shane1

LifeTime Supporter
Apr 29, 2010
621
Buckeye, AZ 85326
Interesting post. I tried switching to bleach, but I changed my mind and went back to the pucks. I'm going to leave the pucks in and see what happens. My CYA is at 80ish as of last night. It's melt your face off hot here right now and will be like this till mid September. My pool gets nothing but sun all day, I have a cartridge filter so I dont backwash. I have a feeling though that backwashing is the key to a TF puck pool.
 

anonapersona

TFP Expert
LifeTime Supporter
Nov 5, 2008
2,598
Shane1, with every 4 of the 7 oz pucks you ought to see CYA rise by 10ppm in an 11,872 gallon pool (per the Pool Calculator, Effects of Adding Chemicals, at the bottom).

So, unless you somehow lose CYA it will be over 100ppm in, what, 2 or 3 weeks?
 

Shane1

LifeTime Supporter
Apr 29, 2010
621
Buckeye, AZ 85326
anonapersona said:
Shane1, with every 4 of the 7 oz pucks you ought to see CYA rise by 10ppm in an 11,872 gallon pool (per the Pool Calculator, Effects of Adding Chemicals, at the bottom).

So, unless you somehow lose CYA it will be over 100ppm in, what, 2 or 3 weeks?
Thats the way I understand it. We will get some rains this summer with the monsoons so that will give me some dilution, but then again if I shock with powder it all may be a wash. I'm really interested to see what happens. It does give me confidence to know that if it doesnt work out I can get every thing cleared up with the help form the people of this site....and for that I am thankfull :goodjob:
 

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