CYA in pools

Maclin

Member
Mar 15, 2022
6
Cincinnati
I have a 40,000 gallon pool. I drain it to 2/3ds in the fall and let it refill with rain/snow. For the past 5 years I have had CYA levels way high (by memory I think around 100). Before that it wasn't tested for cya. Right after I learned of the cya overdose I switched to calcium hypochlorite shock from triclor. It didn't help much. So I switched to calcium hypo tablets in the chlorinator and tricolor shock. This helped and the levels are dropping but not as fast as I would like. It seems to me all available tricolor must have massive amounts of cya in it. Its been a year since I added any tricolor and the CYA level is still over 40. Pool stores tell me to drain it to 1/3, refill and test again, if still high, drain 1/3d again, etc. Doing that with a 40,000 gallon pool several times a year to deal with overloaded cya is kind of expensive and a lengthy process. It gets 1/3d fresh water yearly anyway. I did not know about the various warnings like explosions and dissolve problems (the calcium hypo I've used dissolves fine in the chlorinator). I asked an engineer at pentair why they disallow calcium hypochlorite in their feeders. He stopped responding when I asked that question. My question involves putting calcium hypo in a standard chlorinator. Is the explosion risk from direct contact of calcium and sodium chemicals? Has anyone else tried calcium hypo tabs in a standard feeder? At this point my feeder is acclimatized to calcium tabs. If I can get the levels down this year my plan was to maintain cya at the low end of recommended with tricolor shock and continue with calcium tabs in the feeder. Comments?
 

JoyfulNoise

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May 23, 2015
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It's a danger because someone could add regular trichlor tablets to the feeder with calcium hypochlorite in it, seal it back up and then the thing will detonate like a bomb. Also, calcium hypo tablets are typically composed with a binder material that can leave behind a goopy substance which will clog plumbing. Finally, trichlor tabs are acidic and all of the materials the feeder is constructed from are designed to work with low pH solutions. Cal hypo has very high pH and so there's no guarantee that the materials will withstand that.

As CYA of 40 is not high. You can easily manage a pool with 40ppm CYA just suing additions of liquid chlorine.
 

Texas Splash

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Welcome to TFP! :wave: To add to Matt's notes:
- Tri-chlor tabs (w/ stabilizer) and cal-hypo (w/ calcium) all have potential disadvantages when those levels get too high. For that reason we recommend using liquid chlorine or regular bleach to increase and maintain the proper FC level. If you elect to supplement with cal-hypo tabs, use a floater to avoid the feeder issue.
- Be sure to add all of your pool and equipment info to your signature. That makes a big difference on what your proper chemical levels should be. Include which test kit you are using.

 

Toxophilite

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Feb 23, 2022
608
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We have always been on aerobic septic systems which use chlorination in the final "clean water" discharge tanks. Pointless, but that's another debate.

Anyways, we have to use either cal-hypo tab feeders or 6% liquid bleach. Cannot use Di or Tri Chlor tabs at all- would build CYA in tank and pointless in darkness. Plus, there's a risk for cross-contamination and the danger mentioned above with mixing types in chlorine feeds. It's easier to just forbid "pool" grade tabs being used at all and sell cal-hypo tabs for septic systems. Probably good advice for pool feeders and cal-hypo warning, too!

Folks with feeders for tabs have a lot of trouble with fouling, as the cal-hypo tabs are soft and dissolve poorly, melt. They tend to create a mushy mess at times, sometimes swelling and requiring taking the tube down for maintenance. Liquid is the preferred method for that reason.
 
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Bperry

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Aug 20, 2020
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I have a 40,000 gallon pool. I drain it to 2/3ds in the fall and let it refill with rain/snow. For the past 5 years I have had CYA levels way high (by memory I think around 100). Before that it wasn't tested for cya. Right after I learned of the cya overdose I switched to calcium hypochlorite shock from triclor. It didn't help much. So I switched to calcium hypo tablets in the chlorinator and tricolor shock. This helped and the levels are dropping but not as fast as I would like. It seems to me all available tricolor must have massive amounts of cya in it. Its been a year since I added any tricolor and the CYA level is still over 40. Pool stores tell me to drain it to 1/3, refill and test again, if still high, drain 1/3d again, etc. Doing that with a 40,000 gallon pool several times a year to deal with overloaded cya is kind of expensive and a lengthy process. It gets 1/3d fresh water yearly anyway. I did not know about the various warnings like explosions and dissolve problems (the calcium hypo I've used dissolves fine in the chlorinator). I asked an engineer at pentair why they disallow calcium hypochlorite in their feeders. He stopped responding when I asked that question. My question involves putting calcium hypo in a standard chlorinator. Is the explosion risk from direct contact of calcium and sodium chemicals? Has anyone else tried calcium hypo tabs in a standard feeder? At this point my feeder is acclimatized to calcium tabs. If I can get the levels down this year my plan was to maintain cya at the low end of recommended with tricolor shock and continue with calcium tabs in the feeder. Comments?
Depending on your fill water, the calcium may start building up the same way CYA does if you continue using cal-hypo too long. Di-chlor powder and Trichlor pucks are the same basic thing in a different forms so adding them will add CYA. The only thing that doesn’t add anything other than a bit of salt) that doesn’t build up is liquid chlorine (like from Home Depot)

Your other question about the feeder was answered well by others.
 
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Maclin

Member
Mar 15, 2022
6
Cincinnati
I have noticed buildup in the feeder presumably from Calcium Hypo tabs, but so far it has been easy to wash out. I have not had an issue with feeders yet that I could attribute to chemicals. I also have not had an issue with calcium deposit buildup or precipitation, maybe because we in southern Ohio have lots of acid rain. Usually over a year I am raising ph.

My original post had incorrect figures, I had not looked at my notebook. 3 years ago the cyanate levels at the beginning of the season (when the water was diluted by 1/3d by rain/snow water over the winter), was over 150ppm. It caused copper algicide to precipitate copper cyanate, a beautiful, nearly fluorescent, lavender colored powder that lightly coated the bottom of the pool. Luckily the stuff redissolved or broke down by itself after a couple sweepings. But that began my battle with cyanate. Using calcium shock instead of triclor powder lowered cyanate to just over 100ppm. After another winter, again 1/3d rain/snow water added, it was just under 100ppm. So last year I used calcium hypochlorite tablets and triclor shock. Again, it just hung at about 100. From what I can tell 20-30ppm is where it needs to be, and in my experience if using standard triclor powder and tabs it is not possible to get it that low. Shocking the pool with calcium hypo does make the water slightly cloudy (as if using a sand filter), but it clears up after a few days. It is irritating that whoever makes triclor powder and tabs loads all of it with cyanate.
 
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Sunnydaze

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Mar 8, 2021
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It is irritating that whoever makes triclor powder and tabs all of it with cyanate.

There are only so many ways chlorine can be stabilized for packaging and use by consumers. It's a "pick your poison" situation when using powder and tabs. You're adding either cya or calcium. Liquid chlorine is the best option because it has neither. 🙂
 
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Endro32

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Jul 1, 2021
25
Rives Junction, MI
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I also have not had an issue with calcium deposit buildup or precipitation, maybe because we in southern Ohio have lots of acid rain. Usually over a year I am raising ph.

You won't necessarily see calcium buildup at first. Using cal-hypo will increase the calcium hardness of your pool's water, one of the factors that affects your pool's calcium saturation index. You start to see the potential for scaling and precipitation after this has been elevated for some time.

When you drain 1/3 of your water each season, you're also reducing the calcium hardness by 33%, so in the long term this may not end up being a significant issue for you. So while liquid bleach is still preferred as others have stated, I'd at least recommend having a good CH test on hand and using TFP's PoolMath app to watch your CSI throughout the season and make sure it stays in a good range. You can adjust your pH and TA slightly to help keep your CSI down if necessary.

And definitely use bleach when you shock. Trichlor pucks are designed for slow release while water flows over them in a chlorinator, not for instantly raising your pool's free chlorine level like bleach or cal-hypo granules are. Just don't get it on any clothes you care about ;)
 

magiteck

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May 20, 2020
850
Neenah, Wisconsin
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You’ve gotten some good advice here. I’m going to rewind a bit and strongly encourage you to read ABCs of Pool Water Chemistry and Recommended Pool Chemicals.

You first need to understand what you want in your water, and what the chemicals you’re using are adding.

You mentioned copper algecide- that’s another thing you don’t want.

The first rule of TFP is to know what’s in your pool water, and understand exactly how anything you’re adding to the water is going to change that. The ABC’s will help get you on the right path.

If you don’t already, also make sure to get one of the recommended test kits. Test Kits Compared

Step 1: Know what’s in your water.
Step 2: Know what you’re adding to your water.
Step 3: Enjoy one of these: How Clear is TFP Clear? Let's See (Pics Please).
 

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Maclin

Member
Mar 15, 2022
6
Cincinnati
You won't necessarily see calcium buildup at first. Using cal-hypo will increase the calcium hardness of your pool's water, one of the factors that affects your pool's calcium saturation index. You start to see the potential for scaling and precipitation after this has been elevated for some time.

When you drain 1/3 of your water each season, you're also reducing the calcium hardness by 33%, so in the long term this may not end up being a significant issue for you. So while liquid bleach is still preferred as others have stated, I'd at least recommend having a good CH test on hand and using TFP's PoolMath app to watch your CSI throughout the season and make sure it stays in a good range. You can adjust your pH and TA slightly to help keep your CSI down if necessary.

And definitely use bleach when you shock. Trichlor pucks are designed for slow release while water flows over them in a chlorinator, not for instantly raising your pool's free chlorine level like bleach or cal-hypo granules are. Just don't get it on any clothes you care about ;)
Thanks, I think bleach is the way forward.
 

Maclin

Member
Mar 15, 2022
6
Cincinnati
You’ve gotten some good advice here. I’m going to rewind a bit and strongly encourage you to read ABCs of Pool Water Chemistry and Recommended Pool Chemicals.

You first need to understand what you want in your water, and what the chemicals you’re using are adding.

You mentioned copper algecide- that’s another thing you don’t want.

The first rule of TFP is to know what’s in your pool water, and understand exactly how anything you’re adding to the water is going to change that. The ABC’s will help get you on the right path.

If you don’t already, also make sure to get one of the recommended test kits. Test Kits Compared

Step 1: Know what’s in your water.
Step 2: Know what you’re adding to your water.
Step 3: Enjoy one of these: How Clear is TFP Clear? Let's See (Pics Please).
We have 3 big dogs who also swim, and the copper algicides are good for a broader spectrum of things.
 

magiteck

Gold Supporter
May 20, 2020
850
Neenah, Wisconsin
Pool Size
13600
Surface
Vinyl
Chlorine
Salt Water Generator
SWG Type
Solaxx (Saltron) Reliant / Purechlor R5
We have 3 big dogs who also swim, and the copper algicides are good for a broader spectrum of things.
Just be careful; as you introduce copper into your water, the copper stays there. It is not 'consumed' like chlorine is. So the more often you use it, the more copper you keep adding, while the old copper is still there.

At a certain level, copper in the water can cause staining, and also do things like turn blonde hair green.

The only way to remove copper from the water is to drain.

Edited to add: Here's an article from years ago about a child who got sick from swallowing pool water that had a high level of copper in it. I might have a similar worry if the dogs are drinking the water.
 
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magiteck

Gold Supporter
May 20, 2020
850
Neenah, Wisconsin
Pool Size
13600
Surface
Vinyl
Chlorine
Salt Water Generator
SWG Type
Solaxx (Saltron) Reliant / Purechlor R5
Thanks, I did not realize that. That explains why all triclor has it in abundance. That really puts the issue in clearer focus for me.
Since chlorine is a gas, all of the forms of solid/liquid chlorine for pools are chlorine bound to something else. The full chemical names give away what they are adding to the water along with chlorine:

Bleach/Liquid Chlorine = sodium hypochlorite
Cal Hypo = calcium hypochlorite
Dichlor = Dichloroisocyanuric acid
Trichlor = Trichloroisocyanuric acid

Liquid Chlorine is recommended here because it adds nothing but salt (and chlorine) to the water. All other forms of chlorine products add something which can accumulate to undesirable quantities.

Sometimes they'll get crafty and use alternate chemical names, like dichloro-s-triazinetrione for dichlor, but that's just another name for Dichloroisocyanuric acid.
 

Maclin

Member
Mar 15, 2022
6
Cincinnati
Just be careful; as you introduce copper into your water, the copper stays there. It is not 'consumed' like chlorine is. So the more often you use it, the more copper you keep adding, while the old copper is still there.

At a certain level, copper in the water can cause staining, and also do things like turn blonde hair green.

The only way to remove copper from the water is to drain.

Edited to add: Here's an article from years ago about a child who got sick from swallowing pool water that had a high level of copper in it. I might have a similar worry if the dogs are drinking the water.
Thanks for the info.

I test for copper. Since I refill about 12,000+ gallons a year (30%±) it doesn't get high (typically 0.1 to 0.2). I add it at the beginning of the year and let it coast from there. I believe the level for drinking water is 1.3ppm. I've never been close to that. All plumbing is hdpe and pvc, so no contribution there.

The high tech chemical algicides are hard to find hard research data on beyond marketing data, I expect they are proprietary. Maybe someone out there has some real data on what they kill and what the safe levels are? Our tap water reports (Butler County, Ohio) do not disclose lead and copper levels beyond "below EPA action levels", but in the last few years I have not had to add tap water to the pool because we are now getting so much rain yearly I have to drain some out once or twice a summer to maintain skimmer levels. I have to drain a lot out when opening too, because it fills above skimmers over the winter. All the acid rain we get also ensures I've never had high ph, and even using part Calcium Hypo I usually have to raise ph once or so a year.

(I just tested our tap water and its below 0.05ppm)
 

ladylonghorn

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Jan 14, 2016
34
Frisco, TX
Pool Size
16700
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Liquid Chlorine
There are only so many ways chlorine can be stabilized for packaging and use by consumers. It's a "pick your poison" situation when using powder and tabs. You're adding either cya or calcium. Liquid chlorine is the best option because it has neither. 🙂
So are you saying to not use any tabs at all and just as a regular routine, daily adds of liquid chlorine? If yes, how do I calculate how much liquid to add daily if going that route?
 
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