Am I finished SLAMing?

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FailedChemistry

FailedChemistry

Active member
Jul 4, 2013
40
St Louis, Missouri
Pool Size
11813
Surface
Plaster
Chlorine
Liquid Chlorine
Hello Everyone!

Every season seems to bring new challenges as my pool behaves differently each year, and this one is no exception.
2 Weeks ago we had some big thunderstorms roll through the area and as a result, a lot of mud flowed into the pool and it was cloudy for several days.
Wasn't sure if the cloudiness was due to the mud, or possibly algae, so I just assumed it was both.
I cleaned out my cartridge filter (which yielded a ton of mud, by the way!), and started to SLAM. A few days later, once the water looked clear, I cleaned out the filter again, but continued to SLAM as I wasn't passing the OCLT tests.

Several days later, now I'm not sure what's going on with it.
The water looks crystal clear.
Last night I passed the OCLT with only a 1 ppm drop.
But now that the sun is on it, during the day I'm losing around 7 ppm of FC every 2 hours.
This big of a drop makes it really difficult to keep up with it — to maintain a shock level.

Is this a normal amount of drop when SLAMing a pool at around FC 20 ppm? Something inherent to high SLAM numbers?
Would that mean I'm finished? Would the drop be less fast with an FC of around 5 ppm or so?

Or am I simply not finished SLAMming, and I need to be more vigilant. (checking every hour I suppose.)
Any ideas?

Latest test:

FC 13
CC 1
TA 60
CH 475
CYA 40
Water Temp 80ºF

I don't know what the pH is because I forgot, and started the SLAM before checking it.

The app's recommended SLAM level is 16.
I've been aiming for 20 in an attempt to give me some leeway so it doesn't drop below the SLAM Target FC.
But as you can see, I didn't get to it in time, and it dropped from 20 to 13 in only 2 hours.

Thanks for reading.
Any help would be greatly appreciated.
 
FailedChemistry said:
Hello Everyone!

Every season seems to bring new challenges as my pool behaves differently each year, and this one is no exception.
2 Weeks ago we had some big thunderstorms roll through the area and as a result, a lot of mud flowed into the pool and it was cloudy for several days.
Wasn't sure if the cloudiness was due to the mud, or possibly algae, so I just assumed it was both.
I cleaned out my cartridge filter (which yielded a ton of mud, by the way!), and started to SLAM. A few days later, once the water looked clear, I cleaned out the filter again, but continued to SLAM as I wasn't passing the OCLT tests.

Several days later, now I'm not sure what's going on with it.
The water looks crystal clear.
Last night I passed the OCLT with only a 1 ppm drop.
But now that the sun is on it, during the day I'm losing around 7 ppm of FC every 2 hours.
This big of a drop makes it really difficult to keep up with it — to maintain a shock level.

Is this a normal amount of drop when SLAMing a pool at around FC 20 ppm? Something inherent to high SLAM numbers?
Would that mean I'm finished? Would the drop be less fast with an FC of around 5 ppm or so?

Or am I simply not finished SLAMming, and I need to be more vigilant. (checking every hour I suppose.)
Any ideas?

Latest test:

FC 13
CC 1
TA 60
CH 475
CYA 40
Water Temp 80ºF

I don't know what the pH is because I forgot, and started the SLAM before checking it.

The app's recommended SLAM level is 16.
I've been aiming for 20 in an attempt to give me some leeway so it doesn't drop below the SLAM Target FC.
But as you can see, I didn't get to it in time, and it dropped from 20 to 13 in only 2 hours.

Thanks for reading.
Any help would be greatly appreciated.
Click to expand...
Going above SLAM level just wastes chlorine to the sun. That may explain some of that loss. Dont do that.
 
I would go by the OCLT results. If you pass that & water is crystal clear you should be good, but make sure you pass. Maybe run two in a row :ROFLMAO: Measuring loss during the day is tough because there are multiple factors involved (sunlight + potential algae) that you can't differentiate.

edit: and yes, I've learned on here recently that you lose more ppm during sunlight & during the day at high/SLAM FC levels. When you drop back to maintenance level you shouldn't see that much loss, but I'm sure someone more experienced could explain why.
 
Bperry said:
Going above SLAM level just wastes chlorine to the sun. That may explain some of that loss. Dont do that.
Click to expand...
Ok... But if I'm SLAMing at 16, that means I go out and check it as often as I can, then add Chlorine to try to sustain it at 16.
But every time it drops below 16 then it's no longer at SLAM level.
So during the course of SLAMing, rather than dipping below the SLAM level, then back up to SLAM level, then below, then up again repeatedly... I had thought if I kept it higher than the SLAM level, when it inevitably dipped, it would never be NOT at SLAM level.
Right?
Or am I not understanding something?
 
FailedChemistry said:
Ok... But if I'm SLAMing at 16, that means I go out and check it as often as I can, then add Chlorine to try to sustain it at 16.
But every time it drops below 16 then it's no longer at SLAM level.
So during the course of SLAMing, rather than dipping below the SLAM level, then back up to SLAM level, then below, then up again repeatedly... I had thought if I kept it higher than the SLAM level, when it inevitably dipped, it would never be NOT at SLAM level.
Right?
Or am I not understanding something?
Click to expand...
The problem is that going over SLAM level exposes more of the FC to sunlight so that more of it is burning away from the sun than santitizing as well as staying safe for equipment and people. The SLAM ratio was chosen to be a good balance of sanitizing vs wasting chlorine to the sun.

The goal is to maintain the FC at the right level, not ensure it never goes below.
 
Bperry said:
The goal is to maintain the FC at the right level, not ensure it never goes below.
Click to expand...
I appreciate your patience!
I think where I'm getting confused is the difference between "Maintain the FC at the right level" and "Ensure it never goes below."
In my mind those two mean the same thing.

What would "maintain" mean if the FC is allowed to go below the right level?
 
You’ve got the right idea - you do want to maintain slam fc as often as possible & going a scootch over to do so while you must be away is understandable but just know that this will mean it burns off faster also. So the result may only be half as good as you were intending. Doing this for long periods of time uses alot more liquid chlorine which is why we simply recommend to maintain slam fc.

At any rate if you’re crystal clear & passing oclt you’ve about got it licked. Maybe do another night just for insurance.
 
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Fair enough. That makes sense.

I've learned my lesson this season having most of my surplus FC burned off by the sun for a week or two.
An expensive lesson to be sure, but once again I'm glad I came here to ask — because I didn't understand what was happening.

Passed the OCLT the second night as well, and FC has since settled to its normal level.
Thanks everyone!
 
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FailedChemistry said:
Why?
Click to expand...
Its just added insurance in case there is still a tiny bit of algae lingering somewhere, especially since you just barely passed the CC test and are questioning your daily drop in FC.

Heck, I've never had a speck of algae in my pool and I regularly keep mine slightly above target for insurance against normal pool stuff (bird poops in the pool, equipment failure, bunch of people using the pool, I get lazy in my testing, etc.).
 
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FailedChemistry said:
Why?
Click to expand...
Keeping FC at the high end of target gives you more wiggle room away from minimum.
Your pool loses between 3 ppm and 5 ppm FC daily (sometimes more during heavy pool usage).

Pretty sure you don't want to do another SLAM.

Your last test results in PoolMath show your FC was 2.0
That is BELOW minimum for CYA 40.
See the FC/CYA Levels chart and dose for the high side of target - or possibly a bit higher based on your daily loss.

If you notice that you can't hold FC, do an Overnight Chlorine Loss Test
Hopefully you'll pass. If not, SLAM Process
 
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FailedChemistry said:
I'm passing my OCLT each night but I'm still losing an average of 14ppm FC per day.
Not sure an extra 2ppm will help.
Click to expand...
Are you still going over SLAM level? That’s what happens when you do that. If you are AT SLAM and losing 14ppm during the day then theres something odd going on.
 
If you're losing fourteen (14) ppm FC daily, there is a problem.

Did you meet all 3 exit criteria for the SLAM Process?
FC loss 1 ppm or less
CC measured 0.5 or less
Water clear and no visivble algae anywhere - gin clear, not cloudy or hazy

Do not dose FC over SLAM level - it's a waste of chlorine

What test kit are you using? Add it to your signature
How old are the reagents?
 
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Bperry said:
Are you still going over SLAM level? That’s what happens when you do that. If you are AT SLAM and losing 14ppm during the day then theres something odd going on.
Click to expand...
No. Now I'm SLAMing at the suggested level: 16ppm.
But when I check it each night it's at 2ppm. Which as proavia reminded me, is below the minimum for CYA.

So at night I add enough FC to bring it back up from 2 to 16ppm. Then wait an hour, and test to be sure. Then go to bed.
Next morning I've only lost 1ppm. Repeat.

This pool season really has me confused.
 
Are you adding liquid chlorine at any other times besides at night and possibly in the morning?

Is any swimmimg taking place?
 
proavia said:
Are you adding liquid chlorine at any other time besides at night and possibly in the morning?

Is any swimmimg taking place?
Click to expand...
I was adding every 2 hours.
But I was told up above that large FC losses over recommended levels was normal, and that there would be less FC loss at normal levels, and since I was passing OCLT test and the water was clear, and CC was below .5ppm I didn't need to SLAM anymore.
So I stopped.

But each night it's back down to 2ppm.
 
Do you still have the ability to add during the day to make sure that FC stays above minimum for your CYA level.

A bit more research needs to go into figuring out your daily 14 ppm FC loss - but for now, don't let the FC drop below minimum for your CYA.
 
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