Herb Jarrell, PhD, DABCC

OBJECTIVE for TodayTo impress you with the value of being conversant with

chemical names, behavior and concepts so that you will be motivated to pay attention in your fall chemistry classes by:

1) Sharing my unraveling of a mystery called Pool Chemistry

2) Giving my ULTIMATE OVERVIEW of Pool Chemistry

3) Using 1) and 2) to assess LeTourneau University’s pool.

Disclaimer!

WARNING! Attendance to this science seminar may destroy your comfort and security while participating in water-

based recreation.

LeTourneau University can not be held liable or responsible for any changes in, or damages to, brain chemistry resulting

from attendance to this seminar.

Biggest Problem: Obfuscations in the Pool Chemistry Industry

no indication of chemical ingredients listed on packaging

often only pool industry jargon is used on packaging

no indication of purity when there are ingredient lists

no identities of inert ingredients when their amounts are listed

Note: these tend to occur because listing actual ingredients requires the use of their actual chemical names and/or formulas

Herb Jarrell, PhD, DABCC

Unraveling the Maze of Pool Chemistry

I—Sorting out the Industry Jargon for Pool Chemicals

II—Anticipating the Effects of Common Pool Chemicals on pH

III—Balancing the need for “chlorine stabilizer” with optimum levels of the “chlorine sanitizer” itself

IV—Balancing the use of calcium salts with optimum levels of the calcium ion itself

I—Sorting out the Industry Jargon for Common Pool “Chorines”

“unstabilized” chlorines = not a source of cyanuric acid“liquid shock” = 6 or 12 % sodium hypochlorite solutions “dry shock” = Ca (Mg or Li) hypochlorite granules

“stabilized” chlorines = chlorinated cyanuric acids (CA)CA dissolved with one of the “shocks” aboveslow-“acting” = “trichlor” = symclosene fast- “acting”: 1) “dichlor” = dichloro-CA “shock”

2) “monochlor” = monochloro-CA “shock”Note: every form of chlorine except “bleach” is “dry

chlorine”

II—Another Problem: The 4-Fold Mantra of Pool Chemical Suppliers

1 2 3 4 balance sanitize shock algaecide

pH disinfect destroy kill algae pH stabilizers water undesirablesanitizer stabilizer solutes

II—Anticipating the Effects of Common Pool Solutes on pH

Typical Acids and Bases pKA pKCB

monoperoxysulfate-HOSO4−2 <2.0

>12.0hydrogen sulfate-HSO4

− 2.0 12.0[cyanic acid-CNOH 3.46 10.54]“carbonic acid”-CO2(aq) 6.35 7.65

cyanuric acid-(CNOH)3 7.20 6.80hypochlorous acid-ClOH 7.40 6.60ammonium-NH4

+ 9.25 4.75

hydrogen carbonate-HCO3− 10.33 3.67

hydrogen tetraborate-HB4O7− >14 <0

II—Bottom Line: anticipate a chemical’s effect on pH in order to

avoid generating excess salts!

Neutralizing acidity produces salt.

Neutralizing basicity also produces salt.

Eventually, you may have to drain your pool to get rid of all the discomfort of salts—burning and dry skin!

III—Balancing the “chlorine stabilizer” with “chlorine” itself: Chlorine Chemistry

Disinfecting as simply as this chemist could conceptualize it:

Na + + ClO− + H―OH ClO―H* + Na+ + OH− bleach* + water hypochlorous acid + sodium

hydroxideWhy are the sodium compounds the only ionized

chemicals?How would you ensure that [ClO−] = [ClOH]?

Typical disinfecting in the real world:(CClNO)3 + 3H―OH 3Cl―OH + (CNOH)3

symclosene + water bleach* + cyanuric acid

*Note: bleach is the actual “sanitizer” in almost all pools!

Check out the molecular models— they represent the four molecules which, all in equilibrium with each

other, provide “stabilized chlorine”:

symclosene ClOH + dichloro-CA dichloro-CA ClOH + monochloro-

CAmonochloro-CA ClOH + cyanuric acid

Note about “stabilized chlorine”

The life of the “chlorine” is not being extended by being bound to the cyanuric acid molecule.

Rather, the life of the “chlorine” is being extended by the cyanuric acid absorbing UV radiation in lieu of the bleach—which would otherwise be decomposed!

Question: what is the obvious remedy for having to stabilize your “chlorine”?

My ULTIMATE OVERVIEW of Pool Chemistry

#1 objective: providing a safe and attractive swimming environment

#2 objective: preserving your investment in your pool and in your pool equipment

Providing a Good Environment and Preserving the Life of your Pool—I

A. Exclusion of water contaminants

B. Ensuring good quality of water

C. Effective filtration system

D. Effective pool “vacuuming”

A. Exclusion of water contaminantsfrom nonhuman sources

forest litterlawn clippingsrunoff waterblowing dust &

debrisalgal and

bacterial growth

Remedies:-adequate filtering systems-and __________?

A. Exclusion of water contaminants from human sources

sweat & mucusfeces & urinebody lotions leachedskin sloughedunwashed swimwearexcessive pool

chemicals

Remedies: easily accessible

toilets & showers

use of clean swimwear, etc.

good pool chemistry

B. Ensuring good quality of water geological contaminants

heavy metalscarbonatessalt

industrial contaminants

groundwater access to soil contaminants

fertilizer runoff into water sources

saltwater contamination from oil/gas production

C. Effective filtration system

appropriate filtration pore sizesadequate volume of filtration

mediumadequate (pump) flow

D. Effective pool “vacuuming”

adequate scrubbing (tactile surface contact)

absence of sequestered pockets of stagnation (“cesspools”)

Providing a Good Environment and Preserving the Life of your Pool—II

A. Maintaining a pH of 7.4-7.6 (~ the pH of tears)

B. Maintaining a bleach concentration of 2-3 ppm

C. Destroying x ppm chloramines with 10x ppm of oxidants

D. Optimizing concentrations of Ca+2 and other solutes

A. Maintaining a pH of 7.4-7.6This is high enough to: And also low enough to:

prevent burning of mucus membranes

prevent degradation of pool and/or pool equipment

optimize the effectiveness of the bleach

prevent burning of mucus membranes

prevent precipitation of insoluble salts on pool fixtures (“scale”) and pool liners (“stains”)

optimize the effectiveness of the bleach

B. Maintaining a bleach concentration of 1-3 ppm This is high enough to: And also low enough to:

inhibit microbial growth of algae and bacteria

sequester organic substances from human and nonhuman sources in a readily excuded form: chloramines

prevent burning of mucus membranes

Pool-borne Pathogens

athlete‘s foot (fungal)ear infections (bacterial and fungal

gastroenteritis (bacterial, fungal and parasitic)Legionnaire’s disease (bacterial)

C. Destroying x ppmchloramines with 10x ppm oxidants

This is high enough to: But is also so high that it:

destroy chloramines *

*Provided that A, B and D are being accomplished, all the odor and burning sensations experienced in pools are due to the presence of chloramines!

prohibits use of the pool during the chloramine exclusion process!

Chloramine Chemistrymonochloramines = strong odors and burning!(R)2N―H + Cl―OH (R)2N―Cl** + H―OH

dichloramines = stronger odors and more burning! RNH2 + 2ClOH RNCl2** + 2HOH

“trichloramine” = the strongest odor and most burning! NH3 + 3ClOH NCl3** + 3HOHammonia* + bleach nitrogen trichloride

*usual sources: urine,sweat, microbial decomposition of proteins

**Note: none of the chlorine atoms has undergone reduction yet!

Pool Chloramine Oxidants1) Most common type: hypochlorite

Disadvantagesat least an overnight delay in the use of the poolIf not enough is added to completely oxidize the amines,

the chloramines may increase without being destroyed! If cyanuric acid is already too high and too much

“chlorine” is added (especially if it is the dichlor or monochlor form!), the “free chlorine” may remain too high to swim in—indefinitely!

2) Other types: non-disinfecting (-“sanitizing”) oxidantsOnly disadvantage: currently a bit more expensiveBut the one I use (monoperoxysulfate) allows reentry

into the pool after only 15 minutes!

The Nexus of “Stabilized Chlorine” with Chloramine Chemistry

Stabilized chlorine fits the structure of a monochloramine(!): (R)2N―Cl

monochloramines = strong odors and burning!(C2H2N2O2)(CO)N―Cl + H―OH

(C2H2N2O2)(CO)N―H + Cl―OH

Question: how would you eliminate this primary source of monochloramines?

D. Optimizing concentrations of Ca+2 and other solutes

A. Minimize contact between pool surfaces and concentrated forms of pool chemicalsSoluble chemicals—predissolve* each chemical, then

broadcast away from pool sides in proportion to the depth of water and allow each to diffuse before circulating water . Note: when would it be best to add a soluble chemical directly into the pumping system?

*Note: make sure it is okay to predissolve the chemical!Insoluble chemicals—place in skimmer basket or in a

leg of panty hose suspended from side of pool where water enters. Note: when would it be best to add an insoluble chemical directly into the pumping system?

D. Optimizing concentrations of Ca+2 and other solutes

B. Maintain the optimum calcium ion concentration for the type of pool

C. Minimize osmotic strength of solutes below that of your body to prevent irritation of mucus membranes and drying or wrinkling of skin—balance additions of chemicals with additions of fresh water! How can you do this without the pool overflowing?

Providing a Good Environment and Preserving the Life of your Pool—III: Prerequisite Definitions

pH = − log [H+] and ppm = parts per million by mass

Thus ppm = x parts of solute/million parts solution

For example: in 1,000,000 mg of water at pH 7.4, there are 1,000 g (1 L) of water and [10 − 7.4] (0.040 mg) of H+.

For the range 7.4-7.6, the H+ is only 0.040-0.025 ppm!

We are now faced with a dilemma!How can such a small range of H+ concentration (0.025-0.040 ppm) be maintained when it is only about 2% of that required for bleach (1-3 ppm) to “sanitize” the pool and only about 0.1 % of that required for bleach (up to 30 ppm) to destroy chloramines?

Answer?

Add an Effective Buffer!

But…

which one(s)…

and how much?

Prerequisite Chemical Principles: Concepts of Acid-Base Equilibria

For any HB H+ + B− ,

pH = pKA − log([HB]/[B−])

Buffering occurs most effectively when [HB] = [B−],

but [HB] = [B−] only when pKA = pH or pKCB = pOH.

Common Pool ChemicalsPotential Buffer

Solutes? pKA pKCB

monoperoxysulfate-HOSO4−2 <2.0 >12.0

hydrogen sulfate-HSO4− 2.0 12.0

cyanuric acid-(CNOH)3 7.20 6.80hypochlorous acid-ClOH 7.40 6.60ammonium-NH4

+ 9.25 4.75

hydrogen carbonate-HCO3− 10.33 3.67

calcium-Ca+2 12.6 1.4hydrogen tetraborate-HB4O7

− >14 <0 sodium-Na+ 14.8 −0.8

How is our LeTourneau pool doing?

THE ASSOC. OF POOL & SPA PROFESSIONALS LETU POOL

Suggested Chemical Standards for Swimming Pools 8-19-09 8-25-09

pH 7.4 – 7.6 7.5 7.5“free chlorine” (available ClOH) 1.0 – 3.0 ppm

3.4 3.8combined (chloramine) sanitizer 0.0 – 0.2 ppm

0.3 0.4cyanuric acid (stabilizer) 30 – 50 ppm 5 5“total alkalinity” (amt of buffers) 80 – 120 ppm 59 69calcium hardness 200 – 400 ppm 140 130

total dissolved solutes not to exceed 1500 ppm ---- ----over that of pool water

Finally—Some Tips onPool Water Analysis—I

1) Colored pad dip sticks—32, 29 and 7 cents apiece, respectively

Insta-TEST (at Swimming Pool SuperStores): pH unusable!good “free chlorine” and total “chlorine” good cyanurates, “total alkalinity” and total hardness

Aqua-Chem 6 (at Lowe’s and K-Mart): an Insta-TEST lookalike!

hth (at WallyWorld): spuriously high pH!only free ClOH, but bleaches out!good cyanurates, “total alkalinity”, total hardness

Finally—Some Tips onPool Water Analysis—II

2) Wet chemical kits—cheap!

hth (at WallyWorld): good, but only total chlorine and pH

Aqua-Chem (at Lowe’s and K-Mart): equivalent to hth

3) LaMotte analyzer printouts—*no cost at S. Pool SuperStores!*acceptably accurate and precise values for all 6 basic tests plus copper, iron, nitrates, phosphates and total dissolved solids, if needed

May you have many happy returns to your favorite swimming pool, spa, swimming hole or

beach.Study hard!

Dr. J.