Slamming, CC, Break Through Chlorination, is this an issue with the TFP Slamming method?

[paulgyro]

Hi everyone, I wanted to put out a story of my pool troubles, how I solved them, and ask some questions.

A short time ago I got sloppy with my pool maintenance and the FC went to zero with a rainstorm. This resulted in clouding water that was very hard to correct.

I started slamming the pool, got it clear after 3-4 days, at about the 6-day mark I passed the overnight chlorine loss test. Let's just say a week.

At this point it was just trying to get the CC down to <=0.5, this was a major battle (results kept floating between 1 and 1.5). I had faith and just kept SLAMMING the pool.

A week and a half later I was getting frustrated and opened the Taylor Pool & Spa Chemistry book to see what it had to say about CC.

This led me to read the section on "Break Through Chlorination", bottom line their view is if you keep adding chlorine but not enough to break through the CC you are just creating more CC.

Taylor's solution? BREAKPOINT DOSAGE = 10 x COMBINED CHLORINE LEVEL.

I then added 15 FC in liquid chlorine form and tested it in the morning. BAM! CC GONE.

Moral of the story: if you are slamming your pool but keep fighting CC for more then a few days apply a breakpoint dosage of chlorine.

Why doesn’t the TFP Slamming method address this? Am I missing something is the Slamming method missing this? I did a brief search and didn’t see this discussed elsewhere.

It’s not just me or Taylor wouldn’t put it in their pool book.

Thoughts?
Paul

 

[crusemm]

SLAM Process
You never stated what your SLAM level FC or CYA level was, but based on your statement I'm guessing it was less than 15. Recommended CYA is 50 which means SLAM FC is 20. My guess is that your SLAM FC was to low from the beginning, and you never really cleared it.

 

[mknauss]

Any chance of seeing your test data during the SLAM Process? Are you using Poolmath?

 

[paulgyro]

Sorry for the delay, I don't have Pool Math premium so I just keep data in a spreadsheet. Data is below.
Note that my SLAM Target FC was 18, CYA of 45 you'll see often I hit it harder to make sure I stayed at or above the target.

I used Bleach 12.5%

SLAM was from 1/21 to 2/11, 21 days!

Date time	FC	CC
1/21 PM	0​
1/22 5pm	0.5​
1/23 AM	2​	1.5​
1/23 PM	9​	1​
1/24 AM	9.5​	1​
1/24 AM2	14.5​	1​
1/24 PM	13.5​	1​
1/25 AM	10.5​	1​
1/25 PM	12​	1.5​
1/26 AM	11.5​	1.5​
1/26 AM2	12.5​	1.5​
1/26 PM	17.5​	1​
1/27 AM	14​	1​
1/27 PM	13​	0.5​
1/27 PM2	15.5​	0.5​
1/28 AM	14​	1​
1/28 PM	13.5​	1​
1/28 PM2	14​	1​
1/29 AM	10.5​	2.5​
1/29 AM2	14.5​	2.5​
1/29 PM	15​	2.5​
1/30 AM	14.5​	1.5​
1/30 pm	14​	1.5​
1/30 PM2	17​	1.5​
1/31 AM	28​	1.5​
1/31 PM	29​	1​
2/1 AM	24.5​	1​
2/1 PM	24​	1​
2/2 AM	20​	1​
2/2 PM	18.5​	1​
2/2 pm2	17.5​	1​
2/3 AM	17.5​	1​
2/3 PM1	22​	1​
2/3 pm2	21​	1​
2/4 AM	19.5​	0.5​
2/4 pm1	24.5​	1​
2/4 pm2	22​	1​
2/5 AM	21.5​	1.5​
2/5 pm1	19​	1.5​
2/6 AM	20.5​	1.5​
2/6 PM1	19​	1.5​
2/7 AM	20.5​	1​
2/8 AM	20​	1​
2/9 AM	21​	1​
2/10 PM	20​	1.5​
2/11 AM	18​	1​
2/11 PM	20​	0.5​

 

[JoyfulNoise]

See this Thread on why the Breakpoint Chlorination 10X rule is wrong -

Certified Pool Operator (CPO) training -- What is not taught

This thread will discuss some of the topics that are either not taught or are taught with incorrect or incomplete information, at least as far as I can tell from those who have had CPO training. If any of you have had recent CPO training and can comment on whether the following is accurate in...

www.troublefreepool.com

The SLAM already accounts for the amount of chlorine needed to oxidize CCs. You admit your pool was a mess and lax management turned it green. Is it any wonder you were having trouble with CCs? You simply had not added enough chlorine to yet to pass the final criteria of a CC < 0.5ppm. The SLAM is designed to safely handle an algae problem without damaging pool equipment or people. Adding excessive amounts of chlorine can be dangerous and leads to waste since chlorine loss to UV increases with increasing FC. Sometimes SLAMs finish in a few days, others take longer. Yours simply took longer.

 

[paulgyro]

FYI pool was never green, just got clouding. How can you say I didn't add enough chlorine? I stayed well above the SLAM of 18 CC for along time. What's the longest SLAM that you know of and is reasonable? Do you just SLAM forever no matter what? What is the point where it turns to insanity? I personally reached that at Day 21, did the Taylor approach and within HOURS was good based on the TFP SLAM criteria. I'll read the thread that you've attached but I'm just sharing my initial thoughts.

 

[paulgyro]

FYI In the link you provided none of the links supporting the assertion that BREAKPOINT DOSAGE = 10 x COMBINED CHLORINE LEVEL is wrong are active any longer. I'll try to dig them up and post them.

 

[ajw22]

FYI pool was never green, just got clouding. How can you say I didn't add enough chlorine? I stayed well above the SLAM of 18 CC for along time.

Where did you get 18 for the SLAM FC level on FC/CYA Levels?

Your CYA was 50. We always round CYA up and only use whole numbers. You can’t eyeball values in between as the scale is logarithmic, not linear.

SLAM FC for CYA 50 is 20 ppm. Once you got CL to that level things cleared up. A few ppm low on the SLAM Process makes the difference.

 

[JoyfulNoise]

Sorry if my original post was unclear, it was written on a phone. It's not that breakpoint chlorination is wrong, it does exist and it's seen most frequently in hot tubs (because they are low volume/high bather load water bodies). What is the wrong is the 10X rule itself. It's based on a misunderstanding of the chemistry of chloramines and the units they are measured in. It also suggests a continuous dosing based on 10X rather than a cumulative dose. Perhaps these two links will help -

Breakpoint Chlorination

I work at a large (860,000 gallon) high use pool and have had high levels of chloramines the last couple of weeks which started in the middle of a large swim meet with approximately 860 swimmers. We are coming up on another large swim meet and my combined chlorine is still running at .7 ppm...

www.troublefreepool.com

Chloramines and FC/CYA

This post will describe the effects of using Cyanuric Acid (CYA) to lower active chlorine concentration in terms of breakpoint chlorination and the net resulting chloramine production. The basic breakpoint reaction was described by Griffin (1939), but the first reasonable detailed model was...

www.troublefreepool.com

As others have pointed to, you were not consistently holding the 40% FC/CYA ratio suggested by the SLAM and you simply had something in the water that was generating CCs (you can have CCs and high FC at the same time). TFP has seen SLAM's go on for 3 or more weeks and, in those cases, pool owners find all sorts of hidden issues - bacterial growth and algae inside light niches, dirty filters, pool ladders full of stagnant water, etc. There's nothing magical about CCs - they form when chlorine reacts with nitrogen-containing organics, they eventually oxidize to nitrogen, nitrates, or outgas as nitrogen trichloride, and then they are gone; they do not come back and they do not "recycle". Some chemicals, like non-chlorine shock or certain kinds of stain removers, can cause false CCs as well as dirty or improperly cleaned test tubes.

 

[paulgyro]

Where did you get 18 for the SLAM FC level on FC/CYA Levels?

Your CYA was 50. We always round CYA up and only use whole numbers. You can’t eyeball values in between as the scale is logarithmic, not linear.

SLAM FC for CYA 50 is 20 ppm. Once you got CL to that level things cleared up. A few ppm low on the SLAM Process makes the difference.

Where? Pool Math app, enter CYA of 45, select SLAM and it tells me SLAM Target FC: 18

 

[ajw22]

Where? Pool Math app, enter CYA of 45, select SLAM and it tells me SLAM Target FC: 18

GIGO

As I explained CYA should be rounded up to whole number.

 

[paulgyro]

GIGO

GIGO = Garbage In Garbage Out?

As I explained CYA should be rounded up to whole number.

Boo...as an engineer if this is the case the app should do the rounding in it's calculation.

 

[ajw22]

Boo...as an engineer if this is the case the app should doing the rounding in it's calculation.

I agree. I sent it over to the developer.

 

[JoyfulNoise]

I think everyone is getting off-topic here with all the snarky replies and one-up'ing. There are several issues at play here that need to be clarified so that this thread can actually be useful to others that read it and not a garbage pile of "I'm smarter than you" comments.

1. The CYA test scale is logarithmic and, in order to avoid inaccuracies, you don't interpolate values between the graduations marks. If the dot disappears between two graduation marks, then you always pick the HIGHER CYA value. That is just a prudent move based on the fact that the CYA test is not overly accurate and you want to err on the side of caution. Because of that, the OP's CYA should have been 50ppm.

2. Shock level at TFP is always 40% FC/CYA ratio. So for a 50ppm CYA level, the SLAM FC minimum that should be maintained is 20ppm. Anything less than that is going to cause the SLAM to slow down.

3. CC's are not magical chemical compounds. Their chemistry is well defined and follows the normal rules of reaction kinetics and equilibrium chemistry. Therefore, if you have a source of amines in your water (nitrogen bonded to carbon and hydrogens), then the more FC you add, the larger the CC concentration will be until the source of amines is exhausted. Thus, if your FC levels fluctuate, your CC levels will tend to fluctuate too until all of the nitrogen bearing compounds are oxidized. So, the OP's SLAM was never complete because all three criteria were not met - even when the water is clear and holding FC overnight, there is still something there generating CCs. The SLAM is not done. By adding higher doses of FC, you simply oxidized away whatever was causing the issue. It would have gone away eventually at normal SLAM levels too.

4. The SLAM is designed to be as aggressive as possible without compromising bather safety AND pool equipment and surfaces. TFP allows people to safely swim even at SLAM levels because 40% FC/CYA ratio is not necessarily harmful. I personally would not swim in a pool with that much chlorine in it, but others have and have done so without issue. Also TFP has a lot of members that own pools with vinyl liners (in fact, I think the majority of TFP users are vinyl pools). Using excessive amounts of chlorine can be detrimental to vinyl. So yes, you can certainly bomb your pool with lots of chlorine to get faster results (that's what pool service companies do all the time), but it's not necessarily the safest thing to do. It's also a waste of chlorine as the higher the FC level, the greater the rate of chlorine loss to sunlight.

Unless there is anything else, I believe this thread has outlived its usefulness. There are plenty of links in the above thread that talk about breakpoint chlorination and where it is applicable in recreational water treatment.

 

[tim5055]

Contrary to what many believe, TFP does not exist to discuss ALL methods of pool care, but a singular method that has come to be known as Trouble Free Pool care. It involves accurate self testing of your pool water and only adding what the pool needs. We want pool owners to understand that "traditional" methods of pool care as taught by many pool stores are often adding things to your pool that you really don't need. From CYA in stabilized pool products to the UV and ozone in the "lower chlorine" methods we feel you don't want or need them.

Breakpoint Chlorination is one of those areas.

As Matt has pointed out, the method we call a SLAM has been developed to be as aggressive as possible without compromising bather safety AND pool equipment and surfaces. A CC of 5 or 10 would result in someone bringing their pool to a FC or 50 or 100......

Paul, it's your pool and you ae welcome to maintain it in any way you see fit. We just can not advocate this method.

To quote Dave here at TFP:

Throughout TFP, you will read that we suggest certain levels that good science and practical experience has taught us fall within safe ranges.

Further reading of posts here will draw you to the inescapable conclusion that these guidelines work.......in thousands and thousands of pools worldwide.

You may or may not choose to use these methods and guidelines or you may use some and not others. Our goal is to teach you what has been proven time and time again and then let you use that information to your benefit.