29Ppm Chlorine

[openbahr]

Hey guys,

I open my pool my self, thanks to this forum, and in the past I was having problems with my pool not holding chlorine on startup

(good ole chlorine lock).

Thanks to the guys here, I learned about amonia in the water and how it must be eliminated before the pool will hold chlorine, and that I didnt need to spend $35 a bottle for PhosFree.

Thanks Chemgeek and others.

so this year I wasnt messing around. I dumped 10 gallons of liquid chlorine into the ~23,000 gal pool at startup.

Wow, that did it. That was 6 days ago and the levels are still at 29ppm. I know that the levels will come down over time but I am wondering if

it could be damaging my filter or heater. I was low on my Taylor test kit chems so I dont kno my FA or CYA but my PH is very low (7.0).

I will be adding Borax tomorrow to raise PH.

thanks in advance for any help.

Mike

[chem geek]

If you already had CYA in the water, then you should be OK. If not, then that was way too much chlorine. The chlorine level should drop during the day if exposed to the UV in sunlight. In general, you should test first before adding chemicals to the pool.

[openbahr]

Thanks man.

How long do you think it would take the levels to

Drop on their own? We are supposed to have a heat wave

Here in the south jersey area and the kids are

Getting antsy.

If it would take a while, would you recommend

A chemical like Sodium Thiosulfate to lower chlorine levels?

[jkusmier]

Sodium thiosulfate isn't cheap, and you need CYA anyway. I would buy a few 5lb jugs of CYA and a 5-pack of skimmer socks and start adding CYA ASAP - hose out the skimmer basket, place a sock, replace the basket and pour enough CYA to fill the sock. Close the valve to the main/floor drain to increase flow through the skimmer. Check the sock every few hours and keep refilling w/ CYA. Your CYA probably dropped to near zero in the offseason. Per the pool calculator, you'll need to add 123oz of CYA (roughly 10 lbs by weight) to reach 40 ppm for a ~23K gal (non-salt pool) or 184 oz (roughly 15 lbs) to reach 60ppm for a salt pool w/ a chlorine generator (many recommend 65ppm but I'm aiming for nice round numbers). You'd be surprised how quickly it dissolves, and even low levels of CYA will curb the damaging effects of such high FC levels. Once you've reached your target CYA level you shouldn't have to add any unless you have to do partial drains/refills or dump water after heavy rains. Splash out will have a nominal impact on CYA. Good luck, and steer clear of stabilized forms of chlorine like pucks and sticks (although I use them sparingly at opening if I have some around).

[openbahr]

Wouldn't cya hold on to the chlorine??? Still 29ppm

[jkusmier]

As chem geek explains:

"Most of the Free Chlorine (FC) in a pool with CYA is not actually the disinfecting form, hypochlorous acid, nor its relative that is not a strong disinfectant, hypochlorite ion. Instead, most of the chlorine is "attached" to CYA in a series of chemicals called chlorinated isocyanurates. These do not disinfect nor do they appear to inhibit or kill algae, but they are more resistant to breakdown from sunlight. CYA protects chlorine from breakdown from the UV rays of sunlight through two mechanisms: 1) direct shielding by CYA via absorption of the UV rays thus protecting the chlorine at lower depths and 2) CYA combining with chlorine to form more stable, though less reactive (i.e. not a disinfectant nor algaecide) compounds.

The amount that CYA reduces the disinfecting chlorine concentration is huge. At a pH of 7.5, a reasonable rule-of-thumb is that the disinfecting chlorine concentration is reduced by a factor equal to the CYA concentration in ppm. So at 30 ppm CYA, the disinfecting chlorine concentration is 1/30th that found with no CYA and the same FC level. The science behind this has been known for a very long time -- published in 1974.

As for high levels of chlorine being damaging to equipment and bad for swimmers, that is true when there is no CYA in the water, as with indoor pools, but is not true in pools where CYA is used, as with outdoor pools. Yes, even the small amount of disinfecting chlorine in an outdoor pool with CYA is a strong oxidizer and disinfectant and will corrode metal faster than water without such chlorine, but it's very slow compared to having chlorine without CYA."

[openbahr]

I think I am getting it.

My ph is also very low now 7.2 is the lowest the Taylor kit goes and I am at least there.

Do you think it would be smart to raise PH now or should I wait till the FCC comes down?

Thanks so much for your help.... BTW pool store told me to not put CYA. Ugh.

[jkusmier]

I would throw in a few cups of pH up (sodium carbonate). Have you measured TA? Because if it's low then you can also raise pH while raising TA by adding baking soda (sodium bicarbonate).

I would also start adding CYA through the skimmer. If you can't find skimmer socks at your local pool store, a pair of pantyhose will do. But I would start introducing CYA. Hopefully your pool isn't vinyl lined.

[openbahr]

It is vinyl lined.

Is that very bad?

I added a pound of cya I had in the shed in the skimmer though a skimmer sock .

And I went to buy more but they were sold out.

So I bought "instant conditioner" and added half the bottle so far

[jkusmier]

It can fade the liner. Go to Wal-Mart and buy HTH stabilizer and conditioner.

[jkusmier]

On second thought - if pH is 7.2 I'd leave it be. I wouldn't add any pH up or baking soda for now. In fact, if your FC is still reading 29 I suspect your test results are off. FC would have dropped somewhat in 48 hours, even with overcast skies. How old are are your Taylor kit and reagents? They may need replacement. I'd still add some more CYA, stop at 5 lbs until you've ordered a new kit or replacement reagents. You need CYA anyway, and your level should have dropped near to 0 in the offseason, but you should still be cautious before you can test w/ new reagents. Good price on new K-2006 and replacement reagents at http://www.amatoind.com/taylor-test-2006-p-555.html

[openbahr]

I just bought both the powder and drops for FCC test new this week. I am waiting for the reagent for the cya test to come in the mail. I will test again in a few hours but it really has been way up at 29ppm for at least 3 days. The days before that I stopped counting after 12 PPM because I was running low on reagents. But got refills now as I said.

This is crazy.

I ever added a few hundred gallons yesterday to try to dilute it.

I will let you know in a few hours.

[openbahr]

Came down a bit but still at 23ppm.

What is a safe level to swin at??

[openbahr]

Cya reagents just arrived!

And my cya level is now reading about 90-100. UGH!!

I thought for sure that the cya dropped as you thought.

Now what?

Cya- 90

Fc- 23ppm

Ph -- less than 7.0

TA-- 50ppm ( when doing test reagent went from bluish green to orangish at 5 drops, never really went "red" as it says in kit)

I also ran heater to get temp up to 80 degrees in hopes that a higher temp would bring fa down quicker.

[openbahr]

The hell with it.

I dumped a few hundred gallons and refilled

I tested again and I'm still at 23ppm

I called the pools store to see if they had sodium thiosulfate and they were confused. Then I said do you have something that will lower the chlorine levels. They said "oh dechlor" which IS thisolfate or sodium sulfite maybe. No indication on label. How is that legal? so, I bought 3lbs.

Hopefully that works because my kids want to kill me right now.

[openbahr]

FINALLY!!

Only a couple of hours after I added the "dechlor" we are down to 12.5 PPM. (:

[chem geek]

For lowering the chlorine (or bromine or other oxidizer) level, one can also use hydrogen peroxide and it will not leave anything extra in the spa since it converts to oxygen gas when acting as a reducing agent. You use the same volume of 3% hydrogen peroxide as 6% bleach gives in Free Chlorine (FC). Though that's fine for a spa, for a pool with 23,000 gallons you can get 27% hydrogen peroxide in Baquacil Oxidizer Shock where for 23,000 gallons it would take around 6-1/2 cups to neutralize 10 ppm FC.

[openbahr]

Next morning and my fc is only 1.5ppm.

My cya was like 90 so should I not use chlorine tabs (pucks) ??

[chem geek]

You may have overdosed on your chlorine reducer. So now you need to get the chlorine back up. Yes, stop using tabs since your CYA is already high. You'll need to keep the FC at a minimum of 7 ppm with your 90 ppm CYA level. If you do a partial drain/refill to lower the CYA level, then you'll be able to target a lower FC level, but there's nothing wrong with working with what you have as long as you keep the FC up. Though it sounds like a high chlorine level, it really isn't because most of the chlorine is bound to CYA and nearly inactive.

So get some chlorinating liquid or unscented plain bleach (NOT splash-less, outdoor, scented, etc.).

[jkusmier]

Richard, I hope you're well. It's been awhile since I bugged you - and I have quick questions I've been meaning to ask for years now re: CYA. Can chlorinated isocyanurates ever become HOCL, or are they forever bound w/ CYA? If so, what is the process? Just curious, and thanks as always.

Sorry, openbahr, I didn't think your CYA could possibly that high after an offseason, particularly since you opened w/ liquid chlorine only.

[chem geek]

Yes, I'm doing OK. Thanks for asking. The process between the chlorinated isocyanurates (chlorine bound to CYA) and hypochlorous acid (unbound active chlorine) is a chemical equilibrium where it goes back and forth relatively quickly. There are many different forms of chlorinated isocyanurates, but the dominant one has one chlorine and one hydrogen and is negatively charged. I designate it as HClCY^- where the "CY" is the core CYA ring with nothing attached. CYA itself would be represented by H₃CY with all hydrogen and no chlorine attached. The most dominant chemical species at pool pH are represented by the following equilibria:

HClCY^- + H₂O <<<---> HOCl + H₂CY^-

"Chlorine Bound to CYA" + Water <<<---> Hypochlorous Acid + Cyanuric Acid

HOCl <--> OCl^- + H⁺

Hypochlorous Acid <---> Hypochlorite Ion + Hydrogen Ion

The first reaction goes much faster in the left direction than in the right which is why most of the chlorine is bound to CYA, but it is still going back and forth. About half of the chlorine is released by CYA in 4 seconds with the above reaction, but in practice there is another pathway not shown via another chlorinated isocyanurate and that has half released in 0.25 seconds so is in practice what happens when you measure chlorine in the chlorine test kits. The hypochlorous acid gets used up during the test and as it does, more chlorine is released so you end up measuring all the chlorine in the time of the test -- the chlorine bound to CYA along with hypochlorous acid and hypochlorite ion. In the first reaction, half the hypochlorous acid gets bound to CYA in 0.04 seconds when the CYA concentration is 30 ppm. So in order to balance out the forward and reverse reaction rates, which is the definition of equilibrium, you need to have a lot more chlorine bound to CYA than hypochlorous acid.

So you can think of Cyanuric Acid as being able to hold chlorine in reserve releasing it as needed. It is essentially a hypochlorous acid buffer. It's a way of significantly moderating chlorine's strength while providing a reservoir of chlorine so that one does not run out.

[jkusmier]

Thanks Richard. I appreciate the explanation - I suspected some equilibrium, given all I've read of "reserve" but now I understand better. Wet, cloudy season in StL so far - reminds me of 2008, our first full season after building the pool. Upside is the solar cover is working, water feels pretty warm.