No Free Chlorine...even after adding liquid 12% chlorine

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trigirlCT

0
Jul 8, 2014
23
Madison/CT
I am a new pool owner (just moved) and learning a lot! I am a bit confused at what has happened with our pool and need advise before proceeding.

Details: Above ground pool, vinyl liner, 15,000 gal, sand filter, chorinator. We used the tabs at the end of last summer without an issue and have continued with a fresh supply (I know the negatives of this and learning and trying to move away from them). We started off the season wonderful with a clean, clear pool and just minor adjustments to bring everything into line. Everything was great until...

I totally forgot to add chlorine tabs to the pool chlorinator last weekend and there was nothing in it. At some point we were not adding chlorine --- probably for 4-7 days. I really thought I had tested the water but my records showed I missed last weekend. So I wasn't surprised to have an FC=0 yesterday.

Taylor K2006:
FC = 0
CC =0
pH= 7.4
TA= 110
CH = 200
CYA= 50

Other notes: Pool water is blue and clear. We cover our pool with a solar cover almost all of the time and it doesn't get used that frequently. Pool temp is 80. We had a bit of rain so debre on cover went in pool and I vacuumed. I noticed one or two greener spots on the pool bottom which I needed to brush.

What I did: I purchased 12.5% liquid chlorine to add. Added it last night with filter running. I added 3/4 of gallon thinking I would bring the chlorine up to a 6 which would be good for my calculated CYA. I also added chlorine pucks to my chlorinator.

Today I uncovered the pool. Tested. And got the same exact readings as yesterday! No FC or CC! I also grabbed my test strips as a backup and there is no chlorine.

Do you think I have chlorine lock (something eating the chlorine)? Do I need to bring the pool to shock levels? What level would that be and for how long do I keep it at that FC level?

My head is spinning from trying to process all of this information and how do I fix it so advise would be appreciated! Thank you
 
Chlorine lock is a pool store invention to cover up the fact that if you follow their advice you will eventually have issues.

When your FC goes to zero (or even below the minimum for your CYA) you open the door for algae to take hold. Even the water looks clear you could have a low level of algae consuming FC.

You need to :lookhere: SLAM Your Pool

Sounds like you need to brush up on Pool School and don't forget to always maintain minimum FC based on :lookhere: Chlorine CYA Chart
 
You're in good shape.

There's no such thing as "chlorine lock". You're on the verge of a algae outbreak. Your pH and TA are good and CYA level is fine. You need to SLAM (Shock Level and Maintain) your pool now. See here.

Use the Chlorine/CYA chart here to find your shock level for your current CYA level.

Keep the SLAM on until you pass the OCLT.

You have the right kit, so you are good to go.
 
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Thank you! I have been reading more and understand the terms a bit better and it is beginning to make more sense. I am going to run out and purchase more liquid chlorine plenty to spare. I will SLAM the pool and follow the guideline until I pass the OCLT (which I now know what that means!). Hopefully it will go smoothly. I suspected an algae bloom was in the making...My fault for not being on top of our pool.

One last question: I have a sand filter. I don't normally backwash unless there is an increase in pressure of about 10 psi. Would you recommend back washing during or after this process?
 
Thanks Smykowski...I didn't know the percentage. I did note the number after backwashing in May and it was 19. Curr't back currently the pool is at 20psi. I won't backwash until 24.

Got my chlorine. Waiting for the last of the sun to make it's way off the pool and SLAMing will begin.
 
For working folks. I checked the pool at 6am and lost 3ppm's last night so I failed the OCLT on that criteria. Everything else looks good. Clear water, no CC. All other readings are same as yesterday so that is good.

I added chlorine this morning at 6am and also added an excess to hopefully keep the pool at 20ppm (my SLAM), pool is covered, and I have the chlorinator on. Not sure if that was the right thing to do. According to the pool math I was at a 17.5ppm and added 1/2 gal of 12% chlorine so it would increase the free chlorine (in theory) to 22%. Someone will get home at lunch for another reading. I assume it will be low in chlorine again. Is it advisable to add an excess of chlorine? Any rules of thumb to follow? After lunch the next reading we can take will be around 6pm.

How do you handle this when you are working?
 

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trigirlCT said:
For working folks. I checked the pool at 6am and lost 3ppm's last night so I failed the OCLT on that criteria. Everything else looks good. Clear water, no CC. All other readings are same as yesterday so that is good.

I added chlorine this morning at 6am and also added an excess to hopefully keep the pool at 20ppm (my SLAM), pool is covered, and I have the chlorinator on. Not sure if that was the right thing to do. According to the pool math I was at a 17.5ppm and added 1/2 gal of 12% chlorine so it would increase the free chlorine (in theory) to 22%. Someone will get home at lunch for another reading. I assume it will be low in chlorine again. Is it advisable to add an excess of chlorine? Any rules of thumb to follow? After lunch the next reading we can take will be around 6pm.

How do you handle this when you are working?
Click to expand...

Looks like you are doing fine. It's OK to go a little over. For CYA = 50, shock level is 20 and mustard shock level is 29 so going a little higher won't hurt.

You mention you are running your chlorinator, looks like you are using chlorine tabs (pucks). If you are using Tricholor, then using these tabs also increases your CYA. You need to use pool math to see the effects of the tabs on your CYA(not to mention your pH). If you are raising your CYA with pucks then your shock level increases. See the effects of adding chemicals below in Pool Math. If you have increased your CYA to 60 for example, then shock level is 24 and you will not be raising your FC high enough to kill all the algae. If you keep using pucks, you will keep raising CYA, continually rising the shock level.

I would stop using the pucks now and use only liquid chlorine. Especially during the OCLT, you should not be adding anything to your pool overnight.
 
Thanks Rick. I only turned on the chlorinator this morning because I was going to work and wanted to keep the levels high. I will shut it now. Current readings were good. FC=20ppm and all others are holding. I have kept the pool covered so the sunlight will not have as much of an effect. I dumped in more chlorine to be safe till I get home later.

New issue: I am seriously blowing thru R-0871 reagent with k2006 kit. I called all the local pool stores and no one has it. Leslie showed 3 in inventory at a store about 1 hour from me but unfortunately they couldn't locate any. I am going to need to order online. I think I am going to be forced into bringing my next sample to Leslie pools before adding chlorine to adjust to 20ppm. Otherwise I don't think I will have enough reagent to run the test this evening and again in the morning to do my comparison. If that is off by more then 1ppm again, I can adjust in the morning. Unfortunately I doubt if I will have enough reagent to do FC during the day...will need to rely on pool store tomorrow for our numbers.

Any other suggestions?
 
Are you using a 25ml sample or 10ml sample for your FAS-DPD testing?

10ml will save you on reagents. Until you are able to get more R-0871, I would consider using a 5ml sample and counting each drop as 1 FC. This is not as accurate, as a 10ml sample, but should be fine when your FC is high as in your case. This way you will only use half the amount of reagent.

I would order some online ASAP and would not wait. You are not going to get accurate enough results from Pool Store testing to continue the SLAM.

Hope that helps.
 
Rick thanks again! Yes I am using the 10ml which requires 40 drops to get to 20ppm each time. I could do the 5ml instead as you stated. I am looking to order from TFTestkits.net now as recommended in another forum here and hoping to get quick shipping.

I agree with you on the pool store accuracy which is why I started to care for the pool myself. I do have to say that the Leslie Pool's near me does titrate for FC and CC which is apparently new. There numbers are consistent with mine. I only had an issue once...that was all I needed to know testing myself was better, easier, quicker, and cheaper. It is crazy some of the recommendations they make and sometimes they have no clue the reason except that it says so when they input the numbers into the computer! I am sure we all have stories which is why we are here and doing it ourselves. Anyway, I am more of a science person so I really want to understand why and what else it will impact before randomly dumping chemicals in my pool. I prefer the hands-on approach.
 
scott.MI YES! I am doing the OCLT tonite and in the morning with 10ml for accuracy. It's after that because I am running low.

Crossing my fingers and hope I loose less then 1ppm tonite and then I am done and new reagent is on the way!
 
Thank you for walking me thru my first SLAM and answering my questions. Passed OCLT and had a little bit of R-0871 to spare. Thankfully that all worked out! I will be smarter and wiser in the future. Certainly will be on top of my chlorine numbers!
 
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