CYA Disappears in Summer

Shocktop2000

Member
Jul 16, 2019
13
Houston, Texas
14,000 gallon plaster pool with the following readings:

PH - 7.5-7.6
CH - 300
FC - 5
TC - 5
TA - 60
CYA - <30
Water Temp - 90-91 F

This summer I started the season with a CYA somewhere under 30 (no cloudiness at the top of the tube on the Taylor kit). I used trichlor pucks to start the season. I got the CYA to 45-50, and switched over to liquid chlorine. I add muriatic acid to keep the PH in the 7.4-7.6 range. With the hotter temperatures in Houston, I get really light yellow algae outbreaks a few times a summer. It starts on the rocks under my waterfall. As soon as I see any yellow algae coming off during my weekly brushing, I hand brush the entire pool, shock it with Cal Hypo (CH was 180 when I started the summer) up to 30 ppm, vacuum the dead algae with the robot vacuum, and then clean all of the pool equipment. This usually leaves the pool perfect for 6-8 weeks until the next signs of algae appear. I am OK with this process. I always keep the FC up to advised levels for stopping yellow algae. I think with the hot temperatures and extensive landscaping around the pool (dropping debris in daily), yellow algae is just a part of life for the pool. And I am happy to maintain it this way. It never gets out of control or stops the pool's use.

Having said that, I checked my CYA levels last week, and the CYA is back to somewhere under 30. It is likely around 10-15 as the water is cloudy in the tube, but not anywhere near making the dot disappear. My understanding is that unless you have a leak or severe splash out, your CYA levels should stay relatively stagnate over time. Mine is anything but that.

Is there a mixture of warm temperature and algae blooms that will eat the CYA? That is the only thing I can figure. I am not really complaining because using pucks to bring it back up is easier than adding liquid chlorine. But curious chemically if this is a known issue.
 

Dirk

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Nov 12, 2017
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Central California
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Sorry, I can't help with your actual questions. The experts will be along in a bit to help you. But once you get that part figured out... You shouldn't have to live with algae like that. Keep in mind that TFP suggested levels and recommendations are just that: suggestions. Every pool is different and TFP guidelines can't possibly cover all the variables for every pool every where. If it turns out that you were, in fact, maintaining all your levels per TFP, and are still having problems, then it's time to adjust those levels to find what it takes to keep your pool happy and healthy. So maybe up your FC a few notches, or whatever. The correct levels for your pool are what work for your pool.
 
Last edited:

Texas Splash

Mod Squad
TFP Expert
LifeTime Supporter
While CYA seems to be one of those trouble levels that most people struggle with at high levels, it can indeed degrade over time. We are not surprised to see anywhere from 3-5 ppm of CYA disappear each month from that normal chemical process. Add to that the 10-15 +/- testing variation of the test itself and it's easy to see why you may a bit low right now. As it's still quite hot in our region, I would increase the CYA to at least 40, or perhaps even 50 to get you through Sept-Oct.

As for the algae, well.......if that's the process you like to use it's your choice of course. We use the SLAM Process to kill and remove algae. Hope that helps.
 
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mknauss

Mod Squad
TFP Expert
Bronze Supporter
May 3, 2014
35,980
Laughlin, NV
Pool Size
6000
Surface
Fiberglass
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-40
My understanding is that unless you have a leak or severe splash out, your CYA levels should stay relatively stagnate over time. Mine is anything but that.
CYA degrades 3-5 ppm per month with up to 10 ppm or higher per month at water temperatures above 85F or so. With your rain overflow and higher temperatures, your CYA levels are expected. You should be testing CYA monthly during the swim season.
 
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BowserB

Silver Supporter
Jul 29, 2018
393
Katy, Texas
I see the same CYA drop, and I'm in the west Houston area--Katy. I don't have algae appearances, though. You didn't say how you normally chlorinate your pool or what levels you maintain generally. You also didn't mention the source of your chemical levels--that is, what is your test kit, or is it the pool store? Could your chlorine level be insufficient to prevent algae. Incidentally, it is recommended here that you complete a signature that includes all the pertinent information about your pool. It saves time for people wanting to help with problems.

I started in April with CYA of 20 and used tabs in a floater as part of my chlorination so as to raise CYA. I also use 12.5% liquid chlorine from Leslies (still the best price I can find at 16.99 for 4 gallons). When CYA was close to 40 with the TF-100 test kit, I took out the tab floater and continued with liquid chlorine only. Just this weekend, I found CYA had dropped back below 30 again, and I attribute that to rain dilution and water temps at 88-90 most days, so the floater is back in the pool., but I'm still using liquid chlorine to be sure. Daily tests to confirm. I really don't want algae!
 

Jeff J.

Well-known member
Aug 6, 2019
223
Staten Island NY
14,000 gallon plaster pool with the following readings:

PH - 7.5-7.6
CH - 300
FC - 5
TC - 5
TA - 60
CYA - <30
Water Temp - 90-91 F

This summer I started the season with a CYA somewhere under 30 (no cloudiness at the top of the tube on the Taylor kit). I used trichlor pucks to start the season. I got the CYA to 45-50, and switched over to liquid chlorine. I add muriatic acid to keep the PH in the 7.4-7.6 range. With the hotter temperatures in Houston, I get really light yellow algae outbreaks a few times a summer. It starts on the rocks under my waterfall. As soon as I see any yellow algae coming off during my weekly brushing, I hand brush the entire pool, shock it with Cal Hypo (CH was 180 when I started the summer) up to 30 ppm, vacuum the dead algae with the robot vacuum, and then clean all of the pool equipment. This usually leaves the pool perfect for 6-8 weeks until the next signs of algae appear. I am OK with this process. I always keep the FC up to advised levels for stopping yellow algae. I think with the hot temperatures and extensive landscaping around the pool (dropping debris in daily), yellow algae is just a part of life for the pool. And I am happy to maintain it this way. It never gets out of control or stops the pool's use.

Having said that, I checked my CYA levels last week, and the CYA is back to somewhere under 30. It is likely around 10-15 as the water is cloudy in the tube, but not anywhere near making the dot disappear. My understanding is that unless you have a leak or severe splash out, your CYA levels should stay relatively stagnate over time. Mine is anything but that.

Is there a mixture of warm temperature and algae blooms that will eat the CYA? That is the only thing I can figure. I am not really complaining because using pucks to bring it back up is easier than adding liquid chlorine. But curious chemically if this is a known issue.

Are you using one of the recommended test kits? AFAIK, if you are following TFP, you shouldn't have periodic algae outbreaks. When you see the algae, do you do a complete SLAM? If not, you may have never killed it all. You should probably do an OCLT.
 
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Shocktop2000

Member
Jul 16, 2019
13
Houston, Texas
Are you using one of the recommended test kits? AFAIK, if you are following TFP, you shouldn't have periodic algae outbreaks. When you see the algae, do you do a complete SLAM? If not, you may have never killed it all. You should probably do an OCLT.
I use the Taylor Kit for all testing. I believe it is the K2005 as I do not test for chlorine levels by titration. This clearly inhibits the SLAM test.

I always keep the chlorine at the recommended range for CYA levels. Right now, my CYA is below 30. My FC never drops below 3. If I am not trying to raise CYA, I use liquid chlorine. I buy the 2.5 gallon jugs from pinch a penny in Houston ($32 for 12.5 gallons of 10.5% liquid chlorine).

And no, I have never completed the SLAM as advised. I normally just rock it to 30 ppm, clean up the dead stuff and move on. It is a pain in the Rear, but it only happens once every 6-8 weeks or so. And gives me a good excuse to scrub down the plaster.
 

Dirk

Gold Supporter
TFP Guide
Nov 12, 2017
8,624
Central California
Pool Size
12300
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-40
As mentioned, you're free to care for your pool as you see fit, of course. But the TFP methods work. You're mixing and matching advice from multiple sources, including some you've come up with on your own. One of my favorite pearls to share here is to advise against that very MO. It didn't work for me when I tried it. Doesn't sound like it's working for you either. Up to a month ago, I was able to brag that since following TFP instructions 100%, I've had zero algae and zero scaling. Haven't had either for years. (Before TFP, I had both, regularly.) But a month ago I got a little lazy and I let my FC dip. Boom - algae. In my mind, this only further substantiates what I've learned here. Follow it blindly = no problems. Stray from the program = problems. For me, it's proof that I don't need to question.

If dealing with algae every couple months works for you, you're golden. If at some point you want to maintain an algae free pool, we can help you.
 

cadillacmike

Member
Nov 5, 2013
10
West Central FL
I didn't know that CYA levels would drop if it was hot and sunny enough. That's interesting news. I need to get more CYA test reagents.

BTW, there are three pool supply places near me, and NONE of their readings ever matched. I would pull water for all three at the same time from the same place in the pool (where one of the discharge jets is) and bring them to the 3 places. Only Ph came close once but still off by 0.2 each. And not even their recommended levels for the tests matched. It's comical, except for the fact that I don't like overtreating the pool and don't like wasting money on unneeded chemicals. One is leslies and they are always pushing to reduce phosphates to lower than what I deem necessary.
 
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Dirk

Gold Supporter
TFP Guide
Nov 12, 2017
8,624
Central California
Pool Size
12300
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-40
Phosphates? What are. phosphates? Kidding... we don't put much stock in worrying about phosphates around here. We would, of course, if we happened to be selling phosphate rememdies...

You should pull test sample water from about 18" deep, or arm's length, and as far from returns as possible, halfway between deep end and shallow end. Same place each time.
 

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jberns

New member
Aug 8, 2020
4
Northern California
I'm in a particularly hot part of California and my pool water temp goes from 80 to 92 degrees between May to September just from the sun beating on it all day long, no shade in the yard. I also lose about 30 ppm CYA each year and need to re-boost it every April with 5 lbs of "conditioner" granules from home depot. My pool also has a built in hot tub that shares the water and we use that year round, so that's another source of heating the water. This is an 18,000 gallon in ground plaster pool. I use liquid 10% chlorine only and have not had any water problems thanks to the methods outlined on this site.
 

cadillacmike

Member
Nov 5, 2013
10
West Central FL
No way I'm getting that deep with my knes and back. I get as deep as I can though. The retuens are at the halfway point but I'll start taking them away from the jets instead of in front of them.
 

Katodude

Silver Supporter
Aug 22, 2017
1,270
West Palm Beach/Florida
Pool Size
15000
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
Hayward Aqua Rite (T-15)
Take a 1/2” , 6 foot long piece of PVC. Drill a hole in a cap and cap one end of the PVC. Use your finger to cover the hole, stick the pipe into the water about 2 feet. Release you finger, cover the hole and pull out the pipe and put the water in your container. Just like using a straw to sample a drink.

Its what a bunch of us around here do.
 

Dirk

Gold Supporter
TFP Guide
Nov 12, 2017
8,624
Central California
Pool Size
12300
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-40
No way I'm getting that deep with my knes and back. I get as deep as I can though. The retuens are at the halfway point but I'll start taking them away from the jets instead of in front of them.
No hands and knees, don't even have to touch the water in winter:

sample pipe 1.jpg sample pipe 2.jpg

I use it twice each time. Dip once and then use that water to rinse out my sample container. That rinses both the pipe and the container. Dip again for the sample. As Kato describes, It's important to put your thumb over the hole first, then put the pipe in the water, then release your thumb after you get the pipe to depth. That way the water in the pipe is from depth, not any from the surface as you push the pipe down into the water.
 

poolnoobgrandma

Gold Supporter
Sep 15, 2018
570
Seminole, FL
No hands and knees, don't even have to touch the water in winter:

View attachment 157686 View attachment 157687

I use it twice each time. Dip once and then use that water to rinse out my sample container. That rinses both the pipe and the container. Dip again for the sample. As Kato describes, It's important to put your thumb over the hole first, then put the pipe in the water, then release your thumb after you get the pipe to depth. That way the water in the pipe is from depth, not any from the surface as you push the pipe down into the water.
I've been doing this since I saw the recommendation here. I am pretty sure I get water from more than 18 inches deep. Is that a problem?
 

Dirk

Gold Supporter
TFP Guide
Nov 12, 2017
8,624
Central California
Pool Size
12300
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-40
You're fine, you're just trying to avoid anything that would influence test results negatively: so not too near the surface, not too near the bottom, not too near the returns or skimmers, etc. And it's not all that critical anyway. These are just good testing procedures. We're not curing cancer COVID-19...

I believe it's important to be consistent more than anything else: doing your own proceedures the same way each time. That way you'll get more reliable results. So if you see a dip in FC, it's not because you tested one day at one end of your pool, and the next day at the other end, it's because there is actually a dip in FC.
 

Kevinr14

Well-known member
Mar 8, 2021
74
Phoenix, AZ
Pool Size
15000
Surface
Plaster
Chlorine
Liquid Chlorine
This is news to me that cya degrades over summer. I thought the whole point of using liquid chlorine was to avoid adding cya because it never leaves the water and requires a partial drain to remove. So it requires monthly additions of cya in hot regions?
 

poolnoobgrandma

Gold Supporter
Sep 15, 2018
570
Seminole, FL
This is news to me that cya degrades over summer. I thought the whole point of using liquid chlorine was to avoid adding cya because it never leaves the water and requires a partial drain to remove. So it requires monthly additions of cya in hot regions?
I think it depends on how much rain you get, and how much sun you get. Here, in hot, sunny, rainy Florida, we end up having to add cya sometime during the season. It's not like a test daily kind of thing, but it's not set it once and check next year, either. In other places where evaporation is much more of an issue than having to drain due to excessive rain, I think the cya builds up more.
 

mknauss

Mod Squad
TFP Expert
Bronze Supporter
May 3, 2014
35,980
Laughlin, NV
Pool Size
6000
Surface
Fiberglass
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-40
So it requires monthly additions of cya in hot regions?
Test your CYA monthly. Get a floater and a small tub (5lbs) of plain tablets. When you go away for more than a couple days, float a couple tablets to maintain your FC. This will add a touch of CYA. You will lose 10 ppm or so a month in Phoenix. June. July, and August.
 

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