CYA falling faster than "normal"

Westovers

LifeTime Supporter
May 31, 2009
83
Austin, Texas
I seem to be having trouble keeping my CYA level up above 50. (It dropped to 20 in just months.) Is there anything that affects the CYA level besides losing water from the pool and replenishing from tap, rain, etc. (like high pH or TA, or anything)??
 

Richard320

TFP Expert
LifeTime Supporter
Jan 6, 2010
20,815
San Dimas, CA (LA County)
Westovers said:
I seem to be having trouble keeping my CYA level up above 50. (It dropped to 20 in just months.) Is there anything that affects the CYA level besides losing water from the pool and replenishing from tap, rain, etc. (like high pH or TA, or anything)??
Supposedly there is some sort of bacteria that converts CYA into ammonia. Otherwise, it's there and unaffected by the rest. Do you have an auto-fill? Maybe you have a leak somewhere and the autofill keeps you from noticing.
 

Westovers

LifeTime Supporter
May 31, 2009
83
Austin, Texas
No autofill. Just using the hose periodically and occasional rain water. What about measuring CYA at FC shock level? That's when I got the 20 (down from 50 or 60).
 

Richard320

TFP Expert
LifeTime Supporter
Jan 6, 2010
20,815
San Dimas, CA (LA County)
Westovers said:
No autofill. Just using the hose periodically and occasional rain water. What about measuring CYA at FC shock level? That's when I got the 20 (down from 50 or 60).
Are you using drops or strips?

Drops won't care. Strips probably will, as the dye will bleach out or discolor.
 

chem geek

TFP Expert
LifeTime Supporter
Mar 28, 2007
12,082
San Rafael, CA USA
The bacteria that consume CYA and convert it to ammonia should not survive in the pool if there is measurable FC. There is a slow oxidation of CYA by chlorine, but this is usually around 2-3 ppm CYA per month though it seemed to be more like 5 ppm per month for me this year. Perhaps some enzyme product was used that is accelerating the CYA breakdown...a mystery.
 

dschlic1

LifeTime Supporter
Oct 5, 2007
564
Valrico, FL
My experience says differently. I have lost 10-20 ppm of CYA per week with a FC of 2 to 3 ppm. Other signs are a slight haze and a higher than normal chlorine demand. May not be bacteria, possibily be a water borne mold. The haze is from white particles in the water. Very small, but can be see with naked eye against black background. Shocking at very high levels will get rid off it.
 
G

Guest

dschlic1 said:
My experience says differently. I have lost 10-20 ppm of CYA per week with a FC of 2 to 3 ppm. Other signs are a slight haze and a higher than normal chlorine demand. May not be bacteria, possibily be a water borne mold. The haze is from white particles in the water. Very small, but can be see with naked eye against black background. Shocking at very high levels will get rid off it.
The white particles are most likely calcium flakes from your SWG... Just curious, do you know what your phosphates level are?
 

chem geek

TFP Expert
LifeTime Supporter
Mar 28, 2007
12,082
San Rafael, CA USA
dschlic1 said:
I have lost 10-20 ppm of CYA per week with a FC of 2 to 3 ppm.
Wow! We should really try and figure out what is going on with your pool to have such a high CYA loss. So you must be adding more CYA regularly. Assuming your CYA level for your SWG is around 80 ppm before it drops, then that's a drop of 13-25% per week and I doubt there's anywhere near that amount of water dilution (940-1875 gallons) even if you had a leak (unless it was very large). Are your other water parameters stable such as Calcium Hardness (CH)? What is the CH of your pool and your fill water? Did this rapid drop in CYA only start to occur when something else changed such as your seeing these white particles?

If you are trying to maintain a CYA level of 80 ppm as is recommended for an SWG, then your FC level of 2-3 ppm is too low so the higher chlorine demand could be either from having your CYA too low (i.e. not at 80 ppm) or from nascent algae growth.

If there were bacterial (or other microorganism) conversion of CYA into ammonia, then 10-20 ppm CYA would result in a chlorine demand of 25-50 ppm FC or 3.6 to 7.1 ppm FC per day higher than normal and I doubt your higher chlorine demand is that high. So while part of what is going on might be some more resistant mold converting some CYA into ammonia, some of it might be getting broken down by other means, perhaps in the SWG though most people don't see this (at least not as much as you are).
 

chem geek

TFP Expert
LifeTime Supporter
Mar 28, 2007
12,082
San Rafael, CA USA
Westovers said:
I seem to be having trouble keeping my CYA level up above 50. (It dropped to 20 in just months.) Is there anything that affects the CYA level besides losing water from the pool and replenishing from tap, rain, etc. (like high pH or TA, or anything)??
The chlorine oxidation of CYA occurs faster at higher pH so perhaps with the waterfalls and resulting carbon dioxide outgassing the pH gets high there such that CYA breaks down faster. However, this would normally be accompanied by a higher chlorine demand. If your CYA is dropping by 10 ppm per month, then that should result in about 25 ppm FC higher chlorine demand per month or around 0.8 ppm FC per day higher demand which is certainly possible. On the other hand, if the resulting ammonia were formed in the waterfall, it could outgas and not create a chlorine demand.

With your spillway, waterfall and SWG, I presume that your pH may run high, correct? Are you using 50 ppm Borates in the pool? If not, then it might help keep the pH from climbing as high as quickly and that *might* reduce the rate of CYA drop if it's caused by chlorine oxidation of CYA at higher pH.
 

dschlic1

LifeTime Supporter
Oct 5, 2007
564
Valrico, FL
I only have that loss of CYA when the "white haze" is in full swing. When the pool is clean (which it has been for quite some time), CYA loss is 10 ppm or less per month which is in line with CYA loss due to chlorine. My normal chlorine demand is around 2 ppm per day. During a "white haze" event the chlorine demand can reach 5 or 6 ppm per day.
 

chem geek

TFP Expert
LifeTime Supporter
Mar 28, 2007
12,082
San Rafael, CA USA
Mmmm...well this does sound like the "white haze" is some sort of microorganism that "eats" CYA to produce ammonia creating a larger chlorine demand. There is also a larger chlorine demand trying to kill this stuff. It doesn't sound like a typical bacteria as that is usually easily killed by chlorine (except in biofilms, but that would be on surfaces and not free-floating in the water). Could be something like white water/tissue mold.

Any idea what triggers a white haze event? Any guess as to what it might be?
 

Beez

LifeTime Supporter
May 19, 2009
785
Dallas, TX
I have no idea if this is related at all, but my CYA did not seem as persistent this summer as it did last summer. I raised it to 60 in June, and by the beginning of August it was 40. No splash out, no backwashing, minimal dilution.
 

anonapersona

TFP Expert
LifeTime Supporter
Nov 5, 2008
2,598
So, where does CYA come from? Is it something that can be manufactured "better" or "worse"?

Are we seeing a "Walmart Effect" where something thought to be standard and consistent is secretly downsized or cheapened for economic reasons resulting in early demise? (recalling my Irish Spring soap from Walmart that had a large corner shaved off, presumably to reduce the advertised price)

Or is this a "melamine in the milk" event where something has been added to stretch the test data falsely while making the product weaker and cheaper?

Just wondering if those things are even possible with CYA.
 

chem geek

TFP Expert
LifeTime Supporter
Mar 28, 2007
12,082
San Rafael, CA USA
There aren't really varying quality levels of CYA. There can be fillers so you might get something that isn't as pure, but that would show up initially after addition as not increasing CYA as much as you expected.

The oxidation of CYA is a known and documented phenomenon. It's just that it usually is much slower than is sometimes seen. It more typically drops 2-3 ppm per month (at 3 ppm FC with 40 ppm CYA), sometimes 5 ppm per month, and in hot spas it's seen to drop at around 5 ppm per month (at roughly 4 ppm FC with 30 ppm CYA)l. There is also the known effect of bacterial conversion of CYA into ammonia and it looks like we have something similar going on with the "white haze". And remember that these rates of drop don't include the drop from water dilution.
 

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