Curiosity Killed The Cat (because the pool was finally balanced & she had too much free time on her hands!)

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shellydsizemore

shellydsizemore

Active member
May 31, 2023
27
Beaumont, TX
Pool Size
19400
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
Hayward Aqua Rite (T-15)
Background: Mostly curiosity in the science with this question. Learning as much as possible helps things stick better when I'm learning something new. 5th season with our pool, but I took ownership of caring for it just this year. And this group is what finally got me to where I am only spending 15-30 minutes on my pool each day, rather than hours scrubbing, testing, brushing, crying, sweating, yada, yada!

Can someone explain, in layman's terms, why the "industry standard" for FC levels is always 1-4ppm when everything I read from actual owners & non-industry experts says it is based on CYA levels? Even my hayward aquarite says 1-3ppm inside the power box on the sticker with all of the various directions. Their recommended CYA levels are 60-80, yet I've learned it should actually be a percentage of my CYA. Even at the minimum CYA of 60, that would make my ideal FC level 4.5ppm (I believe...based on 7.5%, though that's just off the top of my head so I could be slightly off with that actual percentage...i did not go back & actually look up that # since I use the pool math app for ideal level #s).

And then there are the other questions that come into play with "shocking" & "superchlorinating". Using the pool math app & TFP methods, what gives me that shock level #? You can't find anything out there, industry-wise, that says "to shock your pool, you should bring your FC levels to XXppm" except a few sources here & there that say it should be your CC x10 (I think) or something to that effect.

Questions:
1. Why the 1-3/4 ppm recommendation even by the companies that are not out to sell you chemicals? (i.e. Hayward & other salt cell manufacturers)
2. How is FC shock level calculated?
3. Why is my ideal TA so much lower with a salt pool? (I understand what the TA does as a pH buffer, but don't really understand the science behind it being a lower recommended # than industry standard. Same with CH really, except that recommendation seems to be high than industry standard)
4. With some of my higher FC "encapsulated" by stabilizer, does that really mean it's just sitting there, floating along until it's called up for duty, lol? If the excess (above what's getting used, at any given moment, to actually sanitize) is "locked up", how does it get released when it's needed?

Not looking to read more articles about chemistry, as I've read a TON. These questions are coming after reading all of those articles. Anyway, just curious mostly. No issues at the moment, (finally got the black algae under control after learning that the biggest culprit in keeping chlorine levels stable, after killing the algae, was actually an issue with our aquarite system not making chlorine AT ALL, and this forum's "more about..." links helped me realize it was not even making chlorine & pinpoint what was broken. I FINALLY got past the OCLT!) just looking for an opportunity to learn more so I have to ask less and can help others more effectively!

I can't thank the group here enough for getting me where I am today. Y'all have been AMAZING!
 
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shellydsizemore said:
Questions:
1. Why the 1-3/4 ppm recommendation even by the companies that are not out to sell you chemicals? (i.e. Hayward & other salt cell manufacturers)
Click to expand...
Up until fairly recently the industry ignored the effects of CYA and the need for higher FC as the CYA went higher. This is starting to change as industry leaders are now starting to suggest just what we've known for years. It takes time to change the mindset of "Well we've always done it this way." Will take a long time to change the dogma...and the documentation.
shellydsizemore said:
2. How is FC shock level calculated?
Click to expand...
From the work of chemgeek (Richard Falk) and others. You can multiply your CYA by 40% and be accurate.

Chlorine/CYA Chart

EDIT: You will find a simplified and standardized version of this chart at Pool School, Chlorine / CYA Chart. Chlorine/CYA Chart by Chemgeek FC = Free Chlorine in parts-per-million (ppm) CYA = Cyanuric Acid in parts-per-million (ppm) CYA ........... Min FC3 ..... Target FC ...... Yel/Mstrd...
www.troublefreepool.com www.troublefreepool.com

Pool Water Chemistry

This thread presents my findings so far on pool water chemistry including the following: More Accurate Calcite Saturation Index (CSI) to replace Langelier Saturation Index (LSI) Calculation of ppm HOCl (disinfecting chlorine) at various levels of Total Free Chlorine (FC) and Cyanuric Acid (CYA)...
www.troublefreepool.com www.troublefreepool.com
shellydsizemore said:
3. Why is my ideal TA so much lower with a salt pool? (I understand what the TA does as a pH buffer, but don't really understand the science behind it being a lower recommended # than industry standard. Same with CH really, except that recommendation seems to be high than industry standard)
Click to expand...
TA buffers pH. When you use pucks, which are acidic, higher TA buffers (slows) the acidic affects of the pucks. When you don't have an acidic pressure from the pucks, the higher TA will cause a pH rise (without the pucks). So, with a lower TA, your CO2 outgassing (causing pH to rise) slows, and results in a more stable pH.
shellydsizemore said:
4. With some of my higher FC "encapsulated" by stabilizer, does that really mean it's just sitting there, floating along until it's called up for duty, lol? If the excess (above what's getting used, at any given moment, to actually sanitize) is "locked up", how does it get released when it's needed?
Click to expand...
Think of it this way. The FC is always there. CYA is like sunscreen, it slow the loss of FC to UV.

HOCl (hypochlorous acid) is what sanitizes the pool. It is created when you add chlorine to water. The level of HOCl in the water is dependent on the amount of FC and CYA (see curves below). You need to have enough FC for your CYA to have enough HOCl to kill algae and bacteria. The FC is always there, just "protected" by the CYA.
HOCl.gif
 
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shellydsizemore said:
4. With some of my higher FC "encapsulated" by stabilizer, does that really mean it's just sitting there, floating along until it's called up for duty, lol?
Click to expand...

Yes.

shellydsizemore said:
If the excess (above what's getting used, at any given moment, to actually sanitize) is "locked up", how does it get released when it's needed?
Click to expand...

When you add chlorine to water that contains CYA, the chlorine reacts with the water and CYA to form three compounds, in approximately these proportions:

2.5% Hypochlorous acid (HOCl)
2.5% Hypochlorite ions (OCl-)
95% Stabilized chlorine

HOCl is what does all the disinfecting, and is also what irritates skin and damages equipment.

OCl- doesn't really do any of those things and can be ignored.

The stabilized chlorine is just chlorine held in reserve and somewhat protected from the sun. It doesn't disinfect and it doesn't burn your skin. The key thing is that the water maintains a chemical equilibrium between HOCl and stabilized chlorine -- it tries to maintain the 2.5% / 95% proportions -- so as HOCl is used up, stabilized chlorine slowly changes to HOCl to replace it.
 
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shellydsizemore said:
Can someone explain, in layman's terms, why the "industry standard" for FC levels is always 1-4ppm when everything I read from actual owners & non-industry experts says it is based on CYA levels?
Click to expand...

shellydsizemore said:
Even my hayward aquarite says 1-3ppm inside the power box on the sticker with all of the various directions.
Click to expand...

shellydsizemore said:
Why the 1-3/4 ppm recommendation even by the companies that are not out to sell you chemicals? (i.e. Hayward & other salt cell manufacturers)
Click to expand...

Hayward just finds a reference that they can point to because they have zero interest in getting into the water chemistry aspect and it is just easier to use an external reference.

The table below summarizes the levels that are recommended by The Association of Pool and Spa Professionals (APSP).
Click to expand...

You can ask The Association of Pool and Spa Professionals (APSP) or the Pool & Hot Tub Alliance (PHTA) where they got their numbers, but they will probably have no answer or a very lame answer that just goes in circles and is self referential.

The Pool & Hot Tub Alliance was formed in 2019, combining the Association of Pool & Spa Professionals (APSP) and the National Swimming Pool Foundation (NSPF).

Part of the problem is that there are many agencies that have some overlap with the pool industry, but no one has complete control.

So, you have a giant mix of many different opinions and no clear guidance or rules.

The definition of FAC (Free Available Chlorine) is the sum of Hypochlorous acid and hypochlorite, so if you use the calculations for figuring out the amount of these in the water, then the numbers are different from the simple tests that are done.

The problem is that the definition does not match the tests.

In other words, the tests being done are represented as the sum of HOCl and OCL-, but the test actually tests for HOCl + OCL + all of the chlorinated cyanurics.

We talk about the “Industry” as if it is a single thing, but it is really just many different organizations that all form a loose affiliation with no clear leader.

Until some authoritative reference figures out the actual chemistry and publishes new guidelines, the “Industry” is going to continue to use old outdated science to operate.

Most agencies that could do the necessary research have very little to no interest in spending the necessary time and money to do the research and publish new guidelines.

1690904364653.png

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ANSI/PHTA/ICC-2 2023 American National Standard for Public Pool and Spa Operations and Maintenance

ANSI/PHTA/ICC-2 2023 American National Standard for Public Pool and Spa Operations and Maintenance provides public health officials, industry professionals, and code officials an easily adoptable set of guidelines for the operation and maintenance of all types of public aquatic venues. The...
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ANSI/APSP/ICC-5 2011 (R2022) American National Standard for Residential Inground Swimming Pools

This standard applies to permanently installed residential inground swimming pools intended for noncommercial use as a swimming pool by not more than three owner families and their guests and exceedin
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2022 CPO Manual

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Part of the problem is the liability.

A service person or pool store is in a bad situation because they might know that the chlorine needs to be kept at maybe 6 to 10 ppm, but the accepted industry maximum level is usually 4 to 5 ppm.

So, if they keep the level above 5.0 ppm, they can be accused of malpractice.

If the customer has some issue like equipment damage, liner damage or human medical issues, they can potentially blame the service person and sue them for damages.

It does not matter if the service person is right because the lawyer for the plaintiff only needs to point to Published Industry Standards from an organization like the PHTA and you have exceeded those standards.

You have no way to prove that you are right.

The customer can say “My liner is bleached and it is all your fault and you owe me a new liner and you better pay or I will sue you. The liner manufacturer clearly says that the FC is to be kept at 1 to 3 ppm and the PHTA recommends a level of 1 to 4 ppm so you are liable because you kept the FC at 7 to 9. Also, my daughter, Suzy, has a rash and my heater is leaking and those problems were also caused by your crazy high chlorine levels, so you are responsible. Now pay me 1 million dollars or my attorney will sue you.”.

Local governments that set rules just adopt Published Industry Standards.

The PHTA seems to get their maximum from the EPA, which probably set the limits in the early 1900s and never felt the need to revisit the issue.

Even the PHTA avoids responsibility because they can just refer you to the EPA.

Pool Stores and Service People have been forced to compensate for inadequate chlorine levels by doing things like routine shocking, algaecides, copper and silver ionizers and mineral cartridges, floc, clarifier, phosphate reducers, Ozone, UV, enzymes etc.
 
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So, to answer your main question, the 4 ppm limit was probably conjured up by some random clerk at the EPA in 1921 when they had to figure out a number.

They probably used a combination of an Ouija Board, a roll of the dice, a Magic 8 Ball and the clerk’s lucky number.

So, this has been the magic number ever since and no one has any real interest in challenging it or doing any research to see what the real science is.
 
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JamesW said:
So, to answer your main question, the 4 ppm limit was probably conjured up by some random clerk at the EPA in 1921 when they had to figure out a number.

They probably used a combination of an Ouija Board, a roll of the dice, a Magic 8 Ball and the clerk’s lucky number.

So, this has been the magic number ever since and no one has any real interest in challenging it or doing any research to see what the real science is.
Click to expand...
It’s even worse - the real science is against the real interest. How would stores be making money if pools stop going out of whack?
 
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The 1 - 4ppm FC recommendation comes from drinking water standards which is the purview of the EPA. The CDC is responsible for microbial and epidemiological testing and they establish the levels at which sanitizers need to be in order to have good pathogenic control from the standpoint of public health. The EPA is also responsible for environmental quality and it establishes what qualifies as a “pesticide” and the allowable limits based on industry testing.

So the recommendation for FC simply comes from a combination of EPA and CDC analysis for what is considered “safe” for humans and the environment. Discharging 4ppm FC water into a sewer will not cause damage or environmental disasters. Discharging a 50 gallon drum of concentrated Agent Orange along with muriatic acid and few hundred pounds of ethyl lead anti-knock additive will probably have an “adverse effect” on the local environment (cf., Ohio and burning railroad cars…).

None of these analyses take into account the effects of adding a chlorine buffer like cyanuric acid.
 
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The fact that the industry recognizes the need for periodic “shocking” proves that they know that the chlorine level is inadequate.

If the levels were adequate, then “Shocking” would never be necessary.

Adding more chlorine periodically proves that you know that the regular level is insufficient, so you have to “Catch-Up” by adding a bunch of chlorine at one time and this roller coaster is determined to be better than just maintaining an adequate level in the first place.

You have to dump 5 pounds of calcium hypochlorite into the pool to “Shock” it and this makes the water cloudy for at least 24 hours and no one can swim during the “Shock” period.

Or, you pour in a bunch of copper and your kid’s hair turns green and everyone looks like Oompa Loompas.
 
JamesW said:
Adding more chlorine periodically proves that you know that the regular level is insufficient, so you have to “Catch-Up” by adding a bunch of chlorine at one time and this roller coaster is determined to be better than just maintaining an adequate level in the first place.
Click to expand...
The definition of shock is a sudden, often violent change. The only reason to shock a person or pool is if it's DOA.
 
JamesW said:
That's what I call a typical Saturday.
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I have 123 barrels of Agent Orange to get rid of.

Do you have any idea how much it costs to dispose of a barrel of Agent Orange legally?

It’s very expensive, if you can even find anyone who will take it.

I tried selling it on eBay and the eBay people threw a hissy fit.

I tried burning it in the backyard and all of the neighbors made a big fuss like a bunch of crybabies.

“Oh, my eyes are burning, what are you burning in that giant pit”?

Anywho, now I just dump a barrel or two into the sewer every Saturday and it’s fine.
 
JamesW said:
That's what I call a typical Saturday.
Click to expand...

The benefits of ethyl lead really cannot be overstated ... sadly, all the cry-baby neighbors whine like a bunch of stuck pigs and now my tractor engine knocks ... so I just run my loud tractor in the driveway all weekend long and point the tailpipe at them ...
 
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