It Happened-Zero Chlorine & CYA=Ammonia

[Colorado Pool Gal]

Hi All,

I have thoroughly read and re-read the thread It Can Happen to Anyone By Richard aka Chem Geek. Sorry, I don't know how to create a link to the thread. I found this post after searching similarities to what is happening to my pool. Without a long background of how I got here (bad choices that lead to an algae bloom which I have cleaned up), I will let you know where I am currently and ask some questions.

As of 4pm MDT 6.21.13
FC=0.4ppm
CC=0.8ppm
TC=1.2ppm
pH=7.2
TA=130
CH=280
CYA=20? (There is cloudiness to the sample water but my comparator only measures to 30)
The pool water is clear and pool looks good, however at night the pool lights show some cloudiness.

I have added 8#s of cyanuric acid over the last 5 days with no back-washing only to register maybe 20ppm. I have twice superchlorination (shock) treated the pool with 10x the CC value or more to reduce the CC. Shock value #1 was 20ppm when CC=1.8ppm Shock value
#2 was 15ppm when CC=1.2ppm

As you may have guessed none of this has completely solved my issue. Today, after reading the above mentioned post I purchased an ammonia test kit (salicylate test which matches to shades of yellow to green on a color card) from a local tropical fish store. I used the freshwater match card. My pool does not use saltwater other than the residual from the 8.25% bleach used for chlorination.

Result equals between 1pmm to 2pmm of ammonia! The color match is closer but not equal to 2ppm of ammonia.

Prior to my mistakes, my pool was operating well since opening and a month later with the following readings...
FC=3-4ppm with regular chlorine maintenance.
CC=0.2ppm
pH of 7.5
TA=120
CH=240
CYA=40ppm

CH went up 'cuz I used 73% Cal-Hypo in the 1st shock treatment. Have used only 8.25% bleach in the 2nd shock. I don't know what has caused ph & TA changes. OK, I am not a chemistry whiz, so simple answers are appreciated. Here are my questions.

1. Richard's post states he put in over 68+pmm of chlorine in one day to reduce the CC and remove the ammonia. His pool is 16000 gals, he had 0.8ppm of CC and 2ppm of ammonia when he started the extreme chlorination. Is there a formula to calculate FC ppms I may need based on my pool's #of Gallons, CC, Ammonia values or any other factors I'm not considering?

2. After calculating the amount of needed chlorine should I add, can I do it at one time or need to divide into a #number of additions at certain ppms of chlorine. Richard added chlorine in 5-6 intervals. I'm not sure why or maybe there is not a formula as requested in question #1. I'm hoping I could do it in 1 more shock treatment.

3. Richard added cyanuric acid in between intervals of chlorination. It seems logical to me to add this after the ammonia is 0ppm, but I'm not a chem person. Any guidelines would be helpful.

Thanks,
Kate

 

[zea3]

You want to try to keep the CYA level at least 30ppm so all your chlorine doesn't burn off in the sun before it can oxidize the ammonia. The process for getting rid of ammonia is to use the shock process just like you would for algae. Bring the pool to shock level and keep it there as much as you can until the ammonia is cleared. You can read more about the shock process here. Use the Pool calculator to determine your shock level.

 

[Colorado Pool Gal]

Thanks for the reply. Based on your reply I should get my CYA up to at least 30ppm. However, per my initial post I have tried to do this without success. The 2 shock treatments I have done in the last 5 days has reduced the CC from 1.8ppm to 0.8ppm without CYA at 30ppm. The info I did not think to include is that both shock treatments were started after 7pm (pool is fully shaded by 5pm) and by the morning test at 8am >0.5ppm of FC would register. My pool is not in full sun until 8am. My yard has full coverage of 30+ feet tall spruce trees on the North, West & East sides of the yard and our 2 story house is on the South. I don't think I have had much burn off.

Your reference to The Shock Process did answer the question as to why I should not do one mega shock (40+ppm) at one time. To eliminate damage to pool equipment. I will try to raise the CYA again, but I will also keep shocking (hourly) until I get some decent level of FC and the CC reduces to >0.5ppm. Then I will work on more CYA if it does not raise during the shock process and see if I can get the pool's FC to stabilize.

Wish me luck!
Kate

 

[jblizzle]

Then just keep adding bleach every hour or so until the FC starts to stick around ... then the CC should be lower and then you can get the CYA up a bit to complete the shock process.

You will not damage the pool if you just keep adding FC to target 10ppm or so ... if there is ammonia, the FC will drop very quickly. When the drop slows down, then boost the CYA.

 

[chem geek]

Yeah, as I found out the ammonia test just tells you the minimum you'll need (roughly 8-10x the ammmonia ppm-N amount gives you the chlorine ppm-Cl₂ amount), but there can be partially oxidized CYA that doesn't show up in either the CYA nor ammonia test kits yet chlorine will react with it, plus there can be bacteria and algae as well. So just keep adding chlorine so long as FC is getting consumed. That's what I did. For those who have a stable situation (i.e. such as when opening a pool) and want a rough idea of how much chlorine it will take, they can use a bucket of pool water as a test and see how much chlorine it takes before the chlorine starts to register in the bucket and not get rapidly depleted (it will drop faster than in a pool from outgassing, but we're talking about fast drops over an hour or so, not overnight or 24-hour drops). I didn't do this with my pool because the problem had just occurred and I caught it mid-stream so wanted to stop it immediately.

When creating a new post, there is a button in the editing bar above the window where you type called URL that will create a link or you can hover your cursor over it for the syntax that let's you create a link using different text as with It Can Happen to Anyone - Zero Chlorine, CYA-->Ammonia.