Why is SLAM better than traditional shock?

joboo7777

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First off, this site has been very helpful. Thanks to all the Contributors as the historical archives of data have saved me from making MANY mistakes.

i have reviewed the pool school information and some forum threads on Slaming. I’m trying to understand the science around slaming and why it is better than A traditional shock. I understand The traditional shock process includes the use of Cal hypo which raises Calcium Hardness so this is certainly can be a benefit. Other than that why should I SLAM my pool vs the traditional shock method? Is there a research article that someone can point me to that provides more details/data?

thanks!
John
 

Jimrahbe

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John,

Just to make sure we are both on the same page...

The "traditional shock method" is where you add a couple of bags of pool store powered shock to the pool every week or two..

A SLAM is not something you should have to repeat.. A SLAM is also not a "dump it in and you are done" process..

Basically, the traditional method kills some algae, but it never kills it all.. That is why you have to keep repeating it, over and over..

A SLAM is a process where you bring your FC level up to the point that all the algae dies, and you keep it there until you pass the SLAM criteria, which verifies that all the algae is dead.

Just for reference, I have three saltwater pools that in total have been on the TFP process for over 20 years.. In all that time I have never added a single bag of pool store shock.. At the same time I have never had single algae bloom.

Thanks,

Jim R.
 

ajw22

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The science is that you raise your chlorine to the appropriate level for your CYA and MAINTAIN it at that level for as long as it takes to kill all algae. The SLAM Process has three criteria for the exit of the process that determines no algae exists in the water. Once your pool water is algae free you should not have algae return if you always follow our FC/CYA Chart and maintain proper chlorine levels.

Whatever you think "shocking" your pool is you have no scientific target for how much to "shock" nor do you know when the water is algae free and you are done.
 

mguzzy

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If what you mean by "shock" is like what most of the pool stores in my area refer to, you through some bags of stuff labeled "shock" in the pool and call it done. A SLAM Process is a very deliberate process that has an well defined end point in which you are raising the Chlorine level in your pool to a specific level and holding it there until the SLAM criteria are met. On the surface a pool store "shock" and a SLAM seem the same but they are not. A SLAM is a controlled process, shocking is not.
 

JJ_Tex

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Hey neighbor... as others have said, SLAM is only as needed (hopefully never) and is used to kill algae and can take several days.
Shock can mean a lot of things, but generally involves adding a bag of powdered shock on a regular basis as part of your normal pool maintenance.

The science behind TFP is that we keep test and adjust chlorine very often so that you never allow algae to form.
 

Dirk

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Just for reference, I have three saltwater pools that in total have been on the TFP process for over 20 years.. In all that time I have never added a single bag of pool store shock.. At the same time I have never had single algae bloom.
Hey John, it's great that you're exploring the site, and asking questions. That how all of us learned how to take care of our pools the "TFP way."

The others have covered your question, but I wanted to reinforce what Jim said, because it is the much more important take away. If you consistently follow the guidelines you'll learn here, you'll never have to SLAM (or shock) your pool, like, ever. I never have done either. I did see a little tinge of green last summer, because I dropped my guard and got lazy following the TFP method. It was very minor and cleared right up with a little brushing, and by restoring the chlorine level, which I had let slip. Which only proved for me what I'm sharing with you: learn what we do here and practice it and you'll never see algae again, your water will be crystal clear and bonus: the cost of chemicals will go way down from whatever you've been doing.

I know that sounds too good to be true, but almost a quarter of a million people will back me up. (The TFP site just hit 246,771 members!)
 

joboo7777

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Thank you all for the information. I see a few mention the use of SLAM process for Algae. What about when FC and TC are outside the acceptable parameters? I'm assuming you would use a SLAM for this, correct? If so, why couldn't you just use 1 treatment of traditional shock(aka Cal Hypo) to bring it back in line vs the SLAM process?

Thanks!
John
 

JJ_Tex

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What about when FC and TC are outside the acceptable parameters? I'm assuming you would use a SLAM for this, correct?

That is just simply called adding chlorine.


SLAM is a process meant for dealing with Algae, with an emphasis on Maintaining a FC level and it takes days/weeks to complete:
- Raise your FC to a target level based on your CYA (liquid chlorine is recommended, but you can use cal hypo, trichlor, etc as long as your know the impacts of their extra ingredients)
- Maintain that FC level through testing and chlorine additions done multiple times daily
- Days/weeks later when all of your algae is dead and your water is crystal clear, you end the SLAM

The term shock is generally avoided on this forum because there is no set definition. Sometimes people use the name shock for a product like cal-hypo or trichlor, sometimes they use it as an action like "I shock my pool every sunday". Sometimes they even make up new terms like "I super shocked my pool like the pool store said, and I still have algae".
 

ajw22

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What about when FC and TC are outside the acceptable parameters?

TC = FC + CC?

We don't care about TC. We measure FC and CC.

If FC is low you add chlorine. If FC is high you wait and let it drift down.

If CC > 1 you have algae and time for the SLAM Process

If so, why couldn't you just use 1 treatment of traditional shock(aka Cal Hypo) to bring it back in line vs the SLAM process?

That is why there are three exit criteria to the SLAM Process

You are done when:
CC alone does not indicate the water is truly algae free. So "bringing in line" is necessary but not sufficient.

I suggest you read ABCs of Pool Water Chemistry
 

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Dirk

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What about when FC and TC are outside the acceptable parameters? I'm assuming you would use a SLAM for this, correct?
No, a SLAM is called for when algae is present. As Allen explained, we don't monitor TC. If FC is high, we do nothing. If FC is low, we add chlorine. Technically you can add chlorine by using Cal Hypo, but then you'd also be adding calcium to your pool, which may or may not be needed.

Generally speaking, TFP teaches to test for and monitor about a half dozen chemical parameters. When one of those chemicals is not within range of ideal, we show you the best way to adjust that one chemical. We don't generally recommend "combo products" or pool store "magic potions" because they can add other chemicals that are not needed for the issue at hand, or are outright bad for your pool.

There is a specific scenario where you might want to use Cal Hypo, like if both your FC and calcium were low, but even then that's not the preferred fix, because the chances of the amounts of chlorine and calcium in the dose being exactly what your pool needs is about zero. It's much better to add liquid chlorine and calcium as separate products, in just the amounts your pool needs.

Keep reading here, and more and more of this will come into focus. We have a Pool School here, which is a collection of articles. I prefer the eBook version of our Pool School, because they are the same articles but arranged "end-to-end," so it's a more convenient straight-through read. Give it a shot (at the bottom of the page here):


And keep asking questions. We're happy to answer them.
 

NCMike

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From one newbie to another, Id suggest starting with this video from TFP.


I'm a visual learner and Pool School can be overwhelming diving in cold turkey. TFP has a series of videos on YouTube that helps you get your feet wet with all the terminology being used. I found it was a good intro to TFP and Pool School and it helped me understand Pool School a lot better.

The rest of the videos are here

https://www.youtube.com/channel/UCNgsSPdGSsja_Y2ZmVFaDKg
 

joboo7777

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My apologies, I meant CC, not TC! So if CC is more than .5 from FC this means Algae is or could be present? Is this the only reason for the gap between FC and CC?

As for the video, I've seen it but seems very high level and doesn't go in touch detail.

Hoping I never have to SLAM. ;)

Thanks!!!
John
 

mgtfp

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Adding to what has already been said, another part of the science is that the FC values in the FC/CYA Chart are based on concentrations of "active" chlorine (HOCl - Hypochlorous Acid). In a CYA stabilised pool, most of the FC is actually bound to CYA, where it is protected from UV. It still tests as "free" chlorine (FC) in any FC-test like FAS/DPD, but it's actually not an active sanitizer.

The target FC (without SWG) in the FC/CYA Chart is based on an HOCl concentration of about 0.05ppm, the min FC is equivalent to about 0.03 ppm HOCl. HOCl at SLAM-level is about 10 times higher than at min FC, around 0.3ppm. This level is high enough to kill algae reasonably fast, but still low enough that you can keep using the pool (as long as you can see the bottom of the pool) while maintaining SLAM-level (that's the "M" in SLAM) until all algae has been killed. As a comparison: In a public indoor pool without CYA in the water, the HOCl concentration is almost always much higher than our SLAM-level (with CYA=0, the HOCl-concentration at FC=1 is about 0.5ppm, and at FC=4 it is nearly 2ppm - that is considered "safe" for swimming by authorities responsible for public pools).

The TFP-methodology is based on understanding the water chemistry of CYA-stabilised pools, the result is the FC/CYA Chart, an easy to follow condensation of all the science behind the scenes. The TFP chlorine levels are chosen to be high enough to ensure clear, well sanitised water - but not unnecessarily high. That is the the big misunderstanding that is unfortunately still widespread in the traditional pool industry - even though TFP's FC-levels (as tested in common FC-tests) are often higher than what the traditional industry considers safe (usually somewhere in the 1 - 3 or 4 ppm range), the levels of active chlorine (HOCl) in "traditional" pools can be much higher (by a lot...) in pools without CYA (e.g. resulting in bathing suits lasting less than a season), or much lower in pools with CYA that don't follow the FC/CYA Chart.

Rather than throwing once some unspecified amount of "shock" in the pool, hoping that will be enough to clear the pool, TFP's SLAM-process works on a well defined chlorine level, that will over time clear any green swamp, but will keep the pool usable in the process.

As long as you stick to the FC/CYA Chart, there is no regular "shocking" required. But should FC slip too low and a pool turns green, or there was a faecal accident, a SLAM will clear it, but that is not a one-off dose of "shock", SLAM has to be maintained until all three exit-criteria are passed - that could take any period of time from just one day to a couple of weeks. Once you're done and following the FC/CYA Chart, no regular "shocking" required - there are are number of people round here that never had to SLAM (or "shock") their pools in years.

If you want to dive down the deep end to understand the science behind TFP, then I suggest to just do that - visit The Deep End..., particularly the sticky threads by chem geek at the top of the list:

All the "TFP science" goes back to the 1974 O'Brien scientific paper - at the end of the day (and at the end of this far too long post...), a SLAM is just the science described in that paper applied to a green pool.
 
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Dirk

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My apologies, I meant CC, not TC! So if CC is more than .5 from FC this means Algae is or could be present? Is this the only reason for the gap between FC and CC?
Not quite. They're not compared to each other, or calculated with each other. If your CC test result is > 0.5, then that is a warning sign that algae might be present. That is independent of your FC reading. Certainly, if you get a low FC test result, AND a high CC test result, then you're probably looking at an algae event. The high CC is the "algae indicator," the low FC would likely be the cause. So, again, you're not doing any math between FC and CC, you consider them separately and act upon them differently.

As for the video, I've seen it but seems very high level and doesn't go in touch detail.
This is your learning period. Not everything is going to be crystal clear just now. Ya just gotta muscle through (and ask lots of questions). This is how we all learned this stuff, trust me on that. I would say very few of us haven't read through the Pool School material multiple times! Each time we read it, combined with asking questions, and practicing with our test gear and dosing, it just kinda comes into focus at some point. And not years or months from now, it'll happen real quick. Just keep reading and asking and you'll get there!
 
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mgtfp

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So if CC is more than .5 from FC this means Algae is or could be present? Is this the only reason for the gap between FC and CC?

There can be other reasons for elevated CC levels. For example, most nitrogen based molecules like ammonia or urea react really quickly with FC to form CC. It's not unusual to have high CC after a pool party with a higher bather load (i.e. release of various body fluids into the pool). Maintaining target FC usually gets rid of that, can be accelerated by slightly increasing FC, maybe even in anticipation of a higher bather load to come.

On the other hand, you can have an algae problem without seeing significant CC levels. Best indication (apart from an obviously green pool) is not passing the Overnight Chlorine Loss Test, which is based on accelerated FC losses, not CC levels.
 

joboo7777

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There can be other reasons for elevated CC levels. For example, most nitrogen based molecules like ammonia or urea react really quickly with FC to form CC. It's not unusual to have high CC after a pool party with a higher bather load (i.e. release of various body fluids into the pool). Maintaining target FC usually gets rid of that, can be accelerated by slightly increasing FC, maybe even in anticipation of a higher bather load to come.

On the other hand, you can have an algae problem without seeing significant CC levels. Best indication (apart from an obviously green pool) is not passing the Overnight Chlorine Loss Test, which is based on accelerated FC losses, not CC levels.
Great thanks, it is good to know you can correct CC levels caused by some conditions without SLAM
 

joboo7777

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Just wanted to thank everyone for the quick replies. This has been very helpful and will conintue to research as much as I can. I've maintained reef aquariums for many years so I'm used to managing water parameters. Just not use to managing the Chlorine aspect of things.
 
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mgtfp

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Just wanted to thank everyone for the quick replies. This has been very helpful and will conintue to research as much as I can. I've maintained reef aquariums for many years so I'm used to managing water parameters. Just not use to managing the Chlorine aspect of things.

You're at the right place and you're doing all the right things to get the chlorine aspect covered - just stick around, keep asking, and keep reading.
 

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