Pool won't hold chlorine

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OasisSkr

Member
Jul 22, 2020
10
Northeast PA
Hello All. Having some problems trying to maintain chlorine in my 20,000 gallon pool with vinyl liner. I have a Hayward heater but haven't needed it lately. I have an inline chlorinator but it's been turned off as I've been trying to get my CYA down.

Problem started after a few vitamin c treatments to help with iron staining. Vitamin C works like magic (added polyquat 60 during treatment), followed up with Jack's Pink Stuff. Stain comes back once I add any amount of chlorine, but I've been putting in a bottle a week of Jack's Blue and that seems to keep it to a minimum.

I have dumped more than 50 percent of my pool over the past few weeks - attempting to reduce cya and iron content. I got my cya down from over 100 to 65. I know, still high, but hoping to get a new liner next season and full dump and will never use pucks again.

Anyhow, I've dumped 3 cases of cal hypo and at least 8 bottles of bleach into the pool (four bags at a time, or two bottles at a time). Can't get a reading above 1.4 or 1.5, even a few hours after shock treatment. I know I'm probably not adding enough based on my high CYA.

My question is: Can someone help me calculate exactly how much chlorine I'll need to SLAM? I have a case (12 bags) of cal hypo 73%, four bottles of 12 percent liquid chlorine and a few bottles of chlorox.

Here are my current readings:

FC .4
CC .4
PH 7.1 (using ph meter - might be a little lower on color chart using the drops)
TA 100
CYA 65

using TFT test kit

Thanks for all you do!
 
Rounding up CYA to 70 makes your slam level 28 ppm. I'd add all 4 jugs of 12% & go get more. There's no way of knowing the total amount of chlorine your slam will take. I'd get at least another 10 gals & see how long that lasts. Check FC level when you return from the store & add enough to get to 28. Keep checking & adding every hour or two until chlorine starts to hold.

Chlorine/CYA chart
Pool Math
 
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OK. Thanks. Process has begun. Four bottles in pool and wife's at the pool store now. Water is crystal clear, by the way. Just some light iron staining on the steps. I'm sure the SLAM will bring that back in full force, but I know that it's more important to avoid algae situation.

So, why isn't it safe to use the cal-hypo powder? Liquid sure is a lot easier, anyhow.

Also, I assume my phosphate levels are through the roof, given all the sequestering agent I've added this summer. Once I get my chlorine in line, is this something I have to worry about? From reading your forum, I know high phosphates in general aren't a tragedy, but with a higher CYA and iron staining, should I be concerned?

Thanks again.
 
Last time I had my calcium hardness tested at the pool store (a few weeks ago) it read 30 and they wanted me to add 55 pounds of hardness plus. My first year with the pool, I did add at least 50 pounds but have never been able to maintain, and it seems this is not important with vinyl liner?
 
Chasarms said:
It is very possible that the additional chemicals you are putting in the pool are either causing the chlorine to oxidize rapidly or interfering with your ability to accurately test FC.
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So, you think the Jack's Magic Blue Stuff might be giving me incorrect chlorine readings? If so, I've sure wasted a lot of money on chlorine this past month. Besides ascorbic acid, the only other chemicals I've added have been Pro Team Polyquat 60 and Jack's Magic. Last time i added AA was about a month ago. I have added quite a bit of Jack's sequestering agent, though.
 
OasisSkr said:
So, you think the Jack's Magic Blue Stuff might be giving me incorrect chlorine readings? If so, I've sure wasted a lot of money on chlorine this past month. Besides ascorbic acid, the only other chemicals I've added have been Pro Team Polyquat 60 and Jack's Magic. Last time i added AA was about a month ago. I have added quite a bit of Jack's sequestering agent, though.
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I don't know. But, any chemical you put in a pool has opportunity to react with any other chemical as well as the chemicals in the reagents. I would just want to know exactly what is in the various colors of "stuff," and how they may react with chlorine and/or reagents.
 
Chasarms said:
I don't know. But, any chemical you put in a pool has opportunity to react with any other chemical as well as the chemicals in the reagents. I would just want to know exactly what is in the various colors of "stuff," and how they may react with chlorine and/or reagents.
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My understanding is that Jacks Magic is well respected company. I looked up the ingredients for Jack's Magic The Blue Stuff and it says ---
Mixture of proprietary diphosphonic and tricarboxylic acids and Phosphorous Acid .

I knew there were phosphates in all the sequestering agents. Last time tested, reading was 700.

Would the high phosphates cause inaccurate chlorine readings?
 

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After four bottles of 12.5 % liquid chlorine, reading was .8 FC and .4 CC.

Also, talked with tech guy from Jack's Magic. He said Blue Stuff is phosphoric acid, which doesn't feed algae and will not mess with test agents. The bad phosphates are orthophosphate.

Also, it's hot as heck here, so maybe the heat is adding to my problem
 
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Four gallons of 12.5% LC should take your pool up 25 ppm of FC. There's no organic that is going to consume it in half an hour while you wait for it to mix and test., and if there was, you'd know it. The pool would look like a sewer.

You either have a chemical in the pool that is interacting with the chlorine, or there is an issue with testing. My guess is the latter.
 
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I did an AA treatment earlier this season and the AA will eat up your chlorine. How much AA did you add? If you added more than was required it will take a while to get past it, how much depending on how heavy the application was.

Following advice I was given here, I have avoided re-staining. That process involves dropping pH to 7.2 and then slowly try to rechlorinate 1ppm at a time. Add a little chlorine (whatever amount yields 1ppm in your size pool and concentration of LC), wait 1/2 hour, test, repeat til chlorine holds, then continue to slowly raise to target. Between each addition evaluate for re-staining. If observed, drop pH to 7.2, add sequestrant (don't overdose, go by label directions), and proceed. The polyquat 60 will also eat up chlorine so important to follow label directions on that as well.

One more thought, you didn't perhaps use Jack's Scale and Copper remover did you? That is sulfamic acid and although very effective, will chew through chlorine for a much longer time.
 
JeanZ1 said:
I did an AA treatment earlier this season and the AA will eat up your chlorine. How much AA did you add? If you added more than was required it will take a while to get past it, how much depending on how heavy the application was.

Following advice I was given here, I have avoided re-staining. That process involves dropping pH to 7.2 and then slowly try to rechlorinate 1ppm at a time. Add a little chlorine (whatever amount yields 1ppm in your size pool and concentration of LC), wait 1/2 hour, test, repeat til chlorine holds, then continue to slowly raise to target. Between each addition evaluate for re-staining. If observed, drop pH to 7.2, add sequestrant (don't overdose, go by label directions), and proceed. The polyquat 60 will also eat up chlorine so important to follow label directions on that as well.

One more thought, you didn't perhaps use Jack's Scale and Copper remover did you? That is sulfamic acid and although very effective, will chew through chlorine for a much longer time.
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Thanks for responding. I did not use Jack’s scale remover. The AA treatment was about a month ago, and I did it exactly as you described, also based on direction from this forum. The problem started right after, as I was never able to get chlorine back in the water. I was adding gradually over a few days, but couldn’t get it above 2. Those first two weeks after, I was afraid to add more than a bottle a day for fear the stain would return. But then it started getting hot, and I realized iron stain is unsightly but algae would cause nightmares. So I started trying to shock, but to no avail.
Right now, after adding 6 bottles of liquid chlorine (12.5%) and 4 bags of cal hypo today, there is light staining and FC is reading 5.8. This is the highest it’s been in a month. There is powder floating around. I’ll check again tomorrow morning.

I don’t think I used too much AA (about a pound and a half), but even if I did, it’s gotta be gone by now. I have used quite a bit of sequestering agent, though.
After the first big dose of chlorine today, I found gray splotches with black particles on the floor of the pool. Possibly black algae? I vacuumed them out and backwashed, then added more shock. It came up very easily. I never had black algae before, but I read that you have to scrub it. This wasn’t like that at all.

And now I’m at 5.8. We’ll see what tomorrow brings. I guess it’s possible something is throwing off the reagents. Pool had been crystal clear up until this afternoon. Slightly hazy right now.

Thanks to everyone who responded
 

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