SLAM ing 3.0ppm combined chlorine

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M

mikefamig

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Jul 10, 2017
299
Connecticut
I'm a new member and have been reading here and elsewhere and am in the process of trying to eliminate a high 3.0 ppm combined chlorine reading (using Taylor dpd-fas test).

Initially the CC was 7.5ppm. I added 3 gallons of 12.5% liquid chlorine and 2 cups of 65% Sustain energizer and this combined with a few inches of new rain water have lowered the CC to 3.0. This was very encouraging but subsequent shocking throughout last week did not continue to lower the CC. It got stuck at 3.5.

I let the chlorine fall to ~5ppm over the weekend so that we could use the pool and then the CC mysteriously (to me) dropped from 3.5 to 3.0ppm.

So now it is Monday and I am back at it. At 9:30am I added 3 gallons of 12.5% liquid chlorine running the filter and an aquabot vacuum to mix well. At 1:30pm I measured 23ppm free chlorine and still 3.0 ppm combined chlorine. At this point I added a fourth gallon of liquid chlorine and will test again this evening.

I am testing with only 5Ml sample of water so as to use less reagent so my accuracy is 1ppm per drop.

So am I on the right track? Am I shocking high enough? What level free cl should I maintain going forward?

Thanks in advance, Mike.
 
Welcome to the forum :wave: as AftonJeeoer said we need your CYA level to make a recommendation. Also if you have not had a chance to look at it, head over to pool School and under the Solving problems link read the defeating algae page, in that article you will find directions for SLAM. Unlike shocking that most pool stores recommend you do weekly, SLAM is a process that once completed successfully does not need to be repeated and regular intervals, only if a problem arises would you have to SLAM again. Many on the forum have gone years without having to SLAM. Also what test kit do you have from your comments is sounds if it is a good one? I am just curious how much FAS/DPD reagent you have you can go through if quickly during a SLAM.
 
AftonJeeper said:
We'll need to know your CYA level to know what the proper shock level is. CYA/FC chart.
Click to expand...

Yes I forgot to include the stabilizer. I was using 50 as my CYA measurement this past week but I just tested again and it is closer to 45ppm. I have a little trouble with calling the turbidity test with my eye so let's say that it's between 40 and 50 or 45. We have had heavy rains lately which would explain it being a little lower.

So with CYA=45 the chart says that I should shock around 18ppm. But then why didn't the combined chlorine get a little lower after 4 hours at 23 ppm free cl? How long does it normally take to see an improvement?

Mike.
 
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I should also mention that the water is clean and beautiful with no sign of any problem. So how big of a deal is it to have 3ppm combined chlorine?I understand that it gases off things that are not good for the swimmer to breathe. should I not be using the pool until the CC is <.5ppm?
 
Mike, that is indeed a significant CC level - both now and back when you first started. It makes one wonder what caused it. Depending on when you opened your pool this season, it could be contaminants from the breakdown of chlorine and stabilizer over the winter. You might have just barley avoided an ammonia outbreak. It could also be residual products from closing ... i.e. antifreeze if used. Some of those products can cause a spike in the CC level until it all gets eliminated by the chlorine and oxidized by the sun. So if you're sure your CYA is close to 50, that's the number I'd recommend referencing for SLAM purposes and use "20" as your SLAM FC level. Try to be as consistent as you can with the FC of 20 and watch it for 2-3 days. The SLAM might take several days, but I would hope the CC numbers begin to drop in the next 48-72 hours or so. Keep us posted.
 
atttech-2 said:
Welcome to the forum :wave: as AftonJeeoer said we need your CYA level to make a recommendation. Also if you have not had a chance to look at it, head over to pool School and under the Solving problems link read the defeating algae page, in that article you will find directions for SLAM. Unlike shocking that most pool stores recommend you do weekly, SLAM is a process that once completed successfully does not need to be repeated and regular intervals, only if a problem arises would you have to SLAM again. Many on the forum have gone years without having to SLAM. Also what test kit do you have from your comments is sounds if it is a good one? I am just curious how much FAS/DPD reagent you have you can go through if quickly during a SLAM.
Click to expand...

I am using the Taylor K-2006 test kit. I'm using a lot of the R0871 in testing chlorine so I bought an additional 2 ounce bottle. The powder and the R0003 are holding up very well and look as though they should get me through this crisis. Amazon has replacements at reasonable prices and deliver quickly.
 
I'm a little embarrassed to admit this but I've cared for this pool for twenty years and mostly just used test strips and trusted them. I used liquid tests very rarely when there was a problem. This year my wife inadvertently added an entire bag of baking powder and drove the total alkalinity over 200 so I bought the K2006 test kit to correct that problem. When I first got the kit my CC was ~0.3 and I have no idea what caused it to go nuts like it did. I'm almost thinking that it never really was as high as 7.5 and maybe I did that test wrong. But that still doesn't explain it being at 3.

Something got in the pool but I have no idea what it was. There are pine and spruce trees and forsythia around the pool. We have a dog but she had not gone in yet. Maybe the neighbors are using the pool when we're out. It's a mystery to me.

Mike.
 
Another question -

When I added three gallons of liquid chlorine this morning the PH was at 7.6. I meant to add a little muriatic acid before the chlorine but forgot. So I ended up adding two cups of MA about a half hour after adding the chlorine. Is that a problem?

Mike.
 
mikefamig said:
Another question -

When I added three gallons of liquid chlorine this morning the PH was at 7.6. I meant to add a little muriatic acid before the chlorine but forgot. So I ended up adding two cups of MA about a half hour after adding the chlorine. Is that a problem?

Mike.
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No.

If you still have the empty container from the sustain energizer, check the ingredients. It looks to me like it's just Cal-hypo, but I could have looked up the wrong thing. If by chance it is monopersulfate, then it's going to interfere with the FC and CC results. Although it should have dissipated by now.

If the pool is otherwise clear looking, I'm wondering if there isn't a mass of organics stuck in the skimmer or the pump strainer or the filter itself that's slowly being oxidized by the bleach and giving you all the CC.

My last suggestion is a real long shot. Years ago someone battled high CC for a week after finishing the SLAM. Turned out to be a dirty test vial.
 

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pookiesunshine said:
i dont see anything in this thread about backwashing; have you done that yet? Richard did mention to check the filter too. good luck.
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Thanks for that but yes I have back-washed twice in the past week because we had so much rain that it was necessary to make the skimmer work and prevent overfilling. I also added some sand to the filter this year and it looked normally clean in there.

Mike.
 
Regarding Richard320's remark about a dirty vial - I just at 6:00pm tested CC of 3.5 and then retested with a vial from an old test kit and the result was just a little less at ~2.5 - 3. Interesting, maybe a fluke or handling but inconclusive. It is still very high CC. I added another gallon of liquid cl to carry it overnight.

Mike.

- - - Updated - - -

I understand that it can take days to complete the slam but when should I expect to see the CC begin to lower? It has been nine hours with no result. Is that expected?
 
mikefamig said:
Regarding Richard320's remark about a dirty vial - I just at 6:00pm tested CC of 3.5 and then retested with a vial from an old test kit and the result was just a little less at ~2.5 - 3. Interesting, maybe a fluke or handling but inconclusive. It is still very high CC. I added another gallon of liquid cl to carry it overnight.

Mike.

- - - Updated - - -

I understand that it can take days to complete the slam but when should I expect to see the CC begin to lower? It has been nine hours with no result. Is that expected?
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No, it's not.

With the sustained high FC I would expect it to be less than 1 CC by now. The water is fairly clear now, yes?
 
mikefamig said:
I have been rinsing the test vial with pool water after testing. Do you think that could affect test results? I'll clean it up with dish soap and water tonight but it's hard to believe that it will help.

Mike.
Click to expand...
Scrub it out good with a bottle brush. Remember, you're talking 3 parts per million. .0003% If it doesn't help, you aren't out much. If it does help, you've saved countless gallons of bleach.
 

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