The SLAM is over, and it's time to transition.

nabril15

Bronze Supporter
May 22, 2011
444
Miami, FL
Hello all, and I wish you safety, health, and patience.
I've always struggled with understanding the transition from slam to normalcy, and so I ask.
I just finished a slam, the numbers look good, and the water is immaculate.
I know that I need to let it drift down to the corresponding cya/fc level, which is easy and fine. The brushing needs to continue daily, and what else? Is there anything else to do?
What I've noticed in the past is that despite passing all 3 conditions of a slam, I've noticed algae when brushing 2 or 3 days after. So then I've returned to slam fc levels, and it continues.
I'd love to be at normal fc levels and stay there; I'm sure that it's possible and achievable..
Thank you
 

Texas Splash

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What I've noticed in the past is that despite passing all 3 conditions of a slam, I've noticed algae when brushing 2 or 3 days after. So then I've returned to slam fc levels, and it continues.
This really shouldn't happen if the SLAM was completed properly and the FC was maintained according to the FC/CYA Chart. But I suspect you already know that which is part of the frustration with the vicious cycle of algae returning. So in those cases we have to see if there are any other potential causes that might impact the chemistry such as:
- High pollen
- Poor water circulation in an area or two
- Hidden area of algae that was extremely small and left undetected, even by the OCLT. This could be something as tiny as a ladder rail partially submerged, light niche, hollow step, or something else that re-bloomed once the SLAM FC level was lowered.

I don't really have a perfect answer as to why your algae would be returning since every pool is different. You really shouldn't have to brush every day, but once or twice a week should be enough. You might review those situations above to see if any apply. Then keep your FC on the upper end of the ideal FC range. As for your chemical levels right now, test everything to be safe. But for sure validate the pH once the FC drops under 10.
 
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nabril15

Bronze Supporter
May 22, 2011
444
Miami, FL
This really shouldn't happen if the SLAM was completed properly and the FC was maintained according to the FC/CYA Chart. But I suspect you already know that which is part of the frustration with the vicious cycle of algae returning. So in those cases we have to see if there are any other potential causes that might impact the chemistry such as:
- High pollen
- Poor water circulation in an area or two
- Hidden area of algae that was extremely small and left undetected, even by the OCLT. This could be something as tiny as a ladder rail partially submerged, light niche, hollow step, or something else that re-bloomed once the SLAM FC level was lowered.
thanks a lot Pat. My only hidden nook is the light niche, and it was exposed during the entire SLAM.
I hope to return to normal FC levels one day and then just stay there with normal maintenance.
 
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nabril15

Bronze Supporter
May 22, 2011
444
Miami, FL
@Texas Splash / other Pool Gods
Pat, another after-thought. The drift of FC from slam level to normal should be a slow one, correct? The drops should be in the 1-2 ppm range per day (perhaps more here in sunny Miami??) If I see huge drops of FC daily, it means that the slam wasn't truly completed.
Is my theory correct?
 

Texas Splash

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Depends on your water temp and amount of sunlight. What is your water temp by the way? When my water temp was close to 80, I might lose about 1-2 ppm of FC in a day or two. Nothing fast. If you are seeing a rapid decline in FC each day, I would be concerned something is still unresolved. :(
 
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nabril15

Bronze Supporter
May 22, 2011
444
Miami, FL
Depends on your water temp and amount of sunlight. What is your water temp by the way? When my water temp was close to 80, I might lose about 1-2 ppm of FC in a day or two. Nothing fast. If you are seeing a rapid decline in FC each day, I would be concerned something is still unresolved. :(
It's 80 degrees at the moment. I'll take a reading this afternoon and one tomorrow morning to see what might be happening.
The water looks Fiji clean, Evian-esque, crystaler than crystal, but unfortunately that is not a genuine indication that everything is fine.
 
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nabril15

Bronze Supporter
May 22, 2011
444
Miami, FL
Tonight's reading is 18 Fc with 0 CC.
So in a 24 hour period, the pool, with no nooks or crannies other than the exposed light niche, dropped from 24 to 18. And today was a cloudy day.
 

Texas Splash

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Sounds like you're losing way too much FC. We should not lose more than 4 ppm in a 24 hour period. Either you don't have enough CYA to protect the FC or you have algae somewhere. You might also to do an Overnight Chlorine Loss Test. You take one last FC reading in the evening after the sun sets, then another test in the morning before the sun hits the water. You don't want the FC to drop more than 1 ppm.
 
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nabril15

Bronze Supporter
May 22, 2011
444
Miami, FL
Dang
@ 1:30pm FC = 16 and I confirmed CYA to be 60, which is what I measured before the SLAM began.
The light niche remains open, and I periodically (every 2 days or so), force the returns to the spa lines and I turn on the air blower; that will move water through those pipes.
Do I need to re-slam? Or should I let it return to the normal range of 7-9 (+ 1 or 2 as suggested by @Texas Splash) and keep an eye on the water clarity, obviously?
 

Texas Splash

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So if I am following your notes correctly, you had an FC of 18 last night, but that was around 7:30 or so. Then you did an FC this morning was 20. There shouldn't be an increase which I guess is why you mentioned possibly a bad sample or test.

That's important for the validity of the Overnight Chlorine Loss Test, so unfortunately we can't say the OCLT was performed correctly to know what the results were. At first glance, today's FC drop from 20 in the morning to 16 mid-way through the day is alarming already. But if that FC test earlier of 20 was incorrect, and perhaps was actually 17 or 18, today's FC drop wouldn't look so bad and you would've passed the OCLT. SO we need to rule-out testing error.

Here's what I would recommend at this time:
1. With a CYA of 60, go ahead and increase the FC to 24 for the remainder of today. Test it one more time after the sun drops to ensure the FC is at 24. That's very important. Leave the pump running on low overnight.
2. For today, give the pool a good brushing and inspect one more time for peace of mind to make sure you didn't miss anything.
3. Tomorrow morning before the sun hits the water, do another FC test. If the number is 23-24, you passed. If the FC drops below 23 tomorrow morning, then you'll need to continue with the SLAM. If the FC is higher than 24, then you know something went wrong with the test.

As a reminder for FC testing: Use a 10 ML water sample size, add one generous scoop of R-0870 powder and mix. Start with the drops until to sample goes clear. Divide the total number of drops in half. Example: 48 drops equals an FC of 24. Count carefully on both tests (tonight and tomorrow morning). A counting error of a drop or two can mean the difference between passing or failing the OCLT. :) Good luck!
 
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nabril15

Bronze Supporter
May 22, 2011
444
Miami, FL
And so Wednesday is upon us.
I took the pool to 24, as instructed by the Splash of Texas, saw the Supermoon, left the single-speed motor on (I wish that I had VS @Texas Splash , and this morning FC = 24 (actually 1 more drop), and CC = 0.
Btw, what do you do if you get an odd number of drops in the FC test, round up or down?

So, I look to be algae free and done with the SLAM. I will take a reading at noon-ish just to test my sanity.
 

Texas Splash

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Glad to hear the OCLT was a success. :goodjob: For FC testing, no need to round up or down that one. If you just happen to use an odd number of drops to get the sample clear that results in an odd number results , just record that number. (example - 25 drops would equal an FC of 12.5)

Now you can just monitor your FC usage each day. As long as the water is crystal clear with no signs of algae and you pass the OCLT, an FC loss of no more than 4 ppm in a 24 hr period is expected to be normal. If you lose more than 4 ppm of FC in a 24 hr period without anything to explain it (i.e. a big swimming party), then it's time to do another OCLT. Hope that helps.
 
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nabril15

Bronze Supporter
May 22, 2011
444
Miami, FL
Thanks a lot Pat. I really appreciate your help.
So, is the OCLT a very good indicator of pool condition? Is it safe to say that (as you said) a daily loss of 4ppm is normal, but if that loss occurs overnight, then algae are blooming? In other words, losing 4 during a normal sunny day is ok, more than that, is bad.
 

Texas Splash

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The OCLT is a great tool. Not always 100%, but very close. That's why we have 3 criteria to evaluate water. So if you pass the OCLT, see no signs of algae, and have less than 0.5 CC, you are considered algae-free. As for normal daily FC consumption, the less used the better, but as temperatures increase, along with swimmers, more FC gets used. Makes sense right? So we expect a pool to lose anywhere between zero and 4 ppm of FC in a 24 hr period. Me for example, I check my FC every evening about 7:00 pm this time of year. As long as I didn't drop more than 4 ppm from last evening, I feel good about the water.

Now if I see that I'm losing more than 4 ppm in a 24 hr period, I have two options: do an Overnight Chlorine Loss Test if I suspect algae, or increase my CYA. If there is ANY doubt about algae, do the OCLT first before increasing the CYA. That's because if you do have to run a SLAM, you prefer a lower CYA to use less bleach/chlorine.

My pool is 100% sun all day. The summer sun in our area is very intense, and my water temp hits the mid to upper 90s in Aug-Sep. So I keep my CYA at about 60 in the summer to protect the FC. I've even taken it up to 70 for a non-salt pool. But I always make sure there is no chance of algae before increasing the CYA.
 

nabril15

Bronze Supporter
May 22, 2011
444
Miami, FL
@Texas Splash
Good morning. I was hoping that yesterday's message would be the closing one, but I remain frustrated with this.
Last night at 8:30, FC read 20, and this morning it reads 17 with CC=0.
So do I need to continue slaming and wasting bleach despite passing the test 2 days ago? My wife and I used the pool yesterday prior to that reading at 8:30. Could that short, 45 minute splash by us have caused a drop to 3 this morning? We weren't wearing sunblock or anything, and we just stood and talked while sipping on rum and coke.
 

Texas Splash

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My wife and I used the pool yesterday prior to that reading at 8:30. Could that short, 45 minute splash by us have caused a drop to 3 this morning?
I don't think so. You validated the FC after the dip, so 20 was your OCLT starting point. This thread started last Sunday, but you claimed you finished a previous SLAM, so something must still be going on. It might be good to see a picture of your pool. Can you post one please?
 

nabril15

Bronze Supporter
May 22, 2011
444
Miami, FL
IMG_20200409_092241.jpg
Gladly. The shadow in the middle ruins the view, but the water is crystal clear.
What I meant is that on Sunday, I finished the slam and passed. I'm trying to transition to normal pool care, but something doesn't jive.
 

Texas Splash

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That water looks like glass. Very nice. :goodjob: So why the excessive FC drop overnight? You lost 3 ppm of FC last night. That is THE question. Well, unless there was a testing (counting) error, it can only be from something organic since the sun was not on the water at any time during the OCLT. But for testing, let me confirm two things: How old are your reagents? And do you use a speedstir to mix the solution?

If there is nothing odd with the testing process, we have to focus our efforts back to the pool and equipment. So I'll ask to confirm the following:
- When was the last time you rinsed-off the cartridges?
- Was the water circulating (low is fine) 24/7 and during the OCLT?
- When was the last time you popped-off that drain cover?
- Have you checked under the skimmer lid for anything odd? Behind the weir door perhaps?

Just looking for any clues now.