Borates & Boric Acid: Uses and Benefits in Pools

2/26/2020

31st NPC Annual Conference

February 12-14, 2020 Houston, TX

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Balancing Using Industry Guidelines May Not work APSP (PHTA) Guidelines for Outdoor Residential Pools Parameter Minimum Ideal Maximum FC (Free Chlorine), ppm 1.0 2.0 -4.0 5.0 CC (Combined Chlorine), ppm 0 0 0.2 pH 7.2 7.4 – 7.6 7.8 TA (Total Alkalinity), ppm 80-100* 60 180 100 – 120** TDS (Total Dissolved Solids), ppm 1,500 NA NA over startup*** CH (Calcium Hardness), ppm 150 200 –400 1,000 CYA (Cyanuric acid), ppm 0 30 –50 100 1 *For cal-hypo, lithium hypo or sodium hypochlorite **For sodium dichlor, trichlor or gas ***Startup includes the TDS contribution of salt found in chlorine generator equipped pools

Confusion with Minimum, Ideal & Maximum

 Minimum level is okay?  Maximum level is okay?  If a condition is between min and max is it okay?  No reasons are given for when min or max level is okay

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All Conditions at Minimum APSP Level

 pH 7.2  TA 60 ppm  TDS 300 ppm  CH 150 ppm  CYA 0 ppm  The Saturation Index would be – 0.80 at 80° F

1 (if using Tables. If using App – 0.66)

All Conditions at Maximum APSP Level

 pH 7.8  TA 180 ppm  TDS 1800 ppm  CH 1000 ppm  CYA 100 ppm  The Langelier Saturation Index would be + 0.76 2 (if using Tables. If using App +0.93)

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All Conditions at APSP Low Ideal Range

 pH 7.4, TA 80 ppm, TDS 300 ppm, CH 200 ppm, CYA 30 ppm and Temp 80°F  Langelier Saturation Index – 0.30  Acceptable Range for LSI is – 0.30 to + 0.50

What are the Right Condition Levels?

 Is a condition okay if within min and max?  How do you decide what is okay?

4 2/26/2020

Replace Ideal Range with a TARGET

Condition Target Notes pH and Alkalinity affect each other pH 7.5 Needs buffering from CYA, TA & Borate You Alkalinity is a buffer against pH decrease. instantly Total Alkalinity 90 ppm Raise by 10 ppm if pH drifts down know if a No Target Not very important in water balance TDS condition Max 1,500 ppm over startup SWG – Salt Level + Start + 1500 ppm is below Saturation Index based on calcium saturation 350 ppm Plaster Pools or above Calcium Min 150 ppm. Max can be higher if source 250 ppm Vinyl, Target Hardness water has high calcium. Offset with lower pH Fiberglass, etc. and TA. Not higher than 50 ppm. CYA is a buffer Cyanuric acid 30 – 50 ppm against pH decrease. CYA controls chlorine available. SWG pools need 70 ppm 3 © Copyright 2018-20 Robert W Lowry Slide 9

pH – Alkalinity Relationship (Buffering)

 Buffers keep the pH from changing  Alkalinity is a pH buffer

High Alkalinity raises pH due to CO2 off-gassing  Low Alkalinity makes pH too easy to change

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Buffering of pH

 Buffers prevent, inhibit or slow down pH change  Alkalinity, CYA and Borate are pH buffers

TA keeps the pH from Going Down

• At pH 8.0 the amounts of acid to lower pH are closer to each other • At pH 7.0 the amounts of acid to lower pH is more. It should take less acid to lower pH • More acid at lower pH means the pH is buffered. • Total Alkalinity prevents pH from Target Total Alkalinity is 90 ppm going down

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TA & CYA Keep the pH from Going Down • CYA also is a pH buffer • It takes more and more acid to change pH as the pH decreases. This shows that CYA and TA are buffering pH against decrease. • Together TA and CYA are the buffer The Target levels are 90 ppm TA and 50 ppm CYA system to prevent 6 © Copyright 2018-20 Robert W Lowry pH from going down

Borate keeps the pH from Going Up • Borate keeps the pH from going up • As pH increases, it takes more and more soda ash to raise pH (It should take less)This shows the buffering against pH increase • Borate is an excellent buffer against pH increase

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TA, CYA & Borate Keep pH from Going Up or Down

Shows TA and CYA are good pH buffers against decrease Shows Borate is a good pH buffer against increase

8 Targets TA 90 ppm, CYA 50 ppm and Borate 50 ppm

TA, CYA and Borate are the pH Buffer System

TA 90 ppm

Borate 50 ppm

CYA 50 ppm

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DEMO Raising pH without Raising Alkalinity

 Aeration, turbulence or splashing raises pH with no change to Alkalinity

 CO2 is driven out of the water and the pH goes up  More later …

Liquid Chlorine does NOT Raise pH

 Liquid chlorine, liquid bleach, cal hypo and lithium hypo (called hypochlorites) will not raise pool water pH  Hypochlorites have a net zero effect on pH  Hypochlorites have a pH from 11.0 to 13.0

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Reactions of Chlorine Products When Added to Water  Cl2 + H2O → HOCl + HCl gas chlorine and water forms hypochlorous acid and hydrochloric acid Each of the hypochlorites + –  NaOCl + H2O → HOCl + Na + OH sodium hypochlorite and water forms hypochlorous acid and sodium ion and hydroxyl ion produce Hydroxyl 2+ – –  Ca(OCl)2 + 2H2O → 2HOCl + Ca + 2OH (Hydroxide OH ) and calcium hypochlorite and water forms hypochlorous acid and calcium ion and hydroxyl ion

+ – HOCl – they raise pH  LiOCl + H2O → HOCl + Li + OH lithium hypochlorite and water forms hypochlorous acid and lithium ion and hydroxyl ion But wait, there’s more …  Cl C N O + 3H O → 3HOCl + H C N O trichlor3 and3 water 3forms hypochlorous3 acid2 and cyanuric acid 3 3 3 3

 NaCl C N O •2H O + H O → 2HOCl + H C N O + Na+ + OH– dichlor dihydrate2 and3 water3 forms3 hypochlorous2 acid and cyanuric2 acid and sodium ion and hydroxyl ion 3 3 3 3

What Happens to HOCl When Used

 Hypochlorite makes hydroxide (OH) – pH goes up   HOCl + UV makes HCl (hydrochloric acid) – pH goes down   HCl made almost equals the OH made – net pH difference is zero or nearly zero  If the pH in your water is always going up, the total alkalinity is too high unless you have a chlorine generator or

9 a negative edge pool or spill overs

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Zero Change to pH from Hypochlorites

Outdoor Pools Lose about 1.0 ppm Free Chlorine per Day

 Chlorine loss is 75% in 2 hours or complete loss in 4 hours  30 ppm CYA keeps chlorine 8 times longer  Residential pools lose 1.0 ppm of chlorine per day even with CYA if in the sun all day  10 ppm per week chlorine demand or consumption (less if in shade)

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Service Techs Use Liquid Chlorine and Trichlor

 10 ppm/week chlorine use difficult to do  Techs use liquid chlorine and trichlor  Problem – trichlor adds more CYA and acid  10 ppm of chlorine added by trichlor, CYA goes up by 6.0 ppm  Leave some liquid with the pool owner, use peristaltic pump, or use a liquid feeder  Supplement with borate, cal hypo tabs, SWG, ozone, UV, AOP, 10 enzymes, or phosphate removers

Increasing CYA Affects Chlorine Kill Rate

 Increasing CYA from trichlor  Affects the kill rate of chlorine  Increases free chlorine needed  Lowers pH and alkalinity  Affects the calculation of the Saturation Index  Wonder why algae starts weeks after startup?  I would suggest not using trichlor – more later  Maximum CYA 50 PPM (70 ppm in summer in sunny regions) 10

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Borates for Pools

 Keeps the pH from going up (pH buffer against pH increase)  Helps prevent algae (it is an algaestat)  Lowers chlorine demand due to algae prevention  Saves 30% to 50% in chlorine use  Water is silkier feeling and sparkles  Add it once and only add more if there is big water loss

Borate as a Buffer

 Acid lowers pH  Base Raises pH  Buffers prevent, inhibit or slow down pH change

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Borate for Pools with SWG

 Pools with SWGs need a level of borate of 70 ppm  Borate keeps pH from going up so there is less calcium carbonate scaling on the hydrogen gas generation plate (cathode) of SWG  Keeping 70 ppm borate lowers free chlorine requirement from 7.5% to 5.0 % (more later)  Less run time for SWG = longer life

Best Water Conditions with SWG Condition Target Notes pH 7.5 – 7.7 Add acid when pH is >7.8 Total Alkalinity 80 - 90 ppm Can lower to 70 ppm if pH is rising

CYA 70 – 80 ppm Add CYA when < 60 ppm

Borate 60 – 70 ppm Add borate when < 50 ppm

Calcium Hardness 350 - 400 ppm Lower calcium when > 500 ppm

Salt 3,000 – 3,400 ppm Use amount recommended by manufacturer

TDS Maximum Start + 1,500 ppm + Salt Include salt with TDS for LSI calculation

Free Chlorine 3.0 to 4.0 ppm – 5% of CYA Chlorine loss to UV is less with higher FC

LSI should be adjusted for CYA and Borate LSI (Sat. Index) – 0.3 to + 0.5 Include salt with TDS for LSI calculation

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Borate is an Algaestat

 Does NOT remove CO2 from the water  Even if borate did remove CO2, when bicarb is added, CO2 is added  Borate disrupts cell wall development, disrupts metabolism and stops cell division

Boric Acid

 I recommend using boric acid  Adding 7.64 oz per 10,000 gallons is 1 ppm boron (B) so 50 ppm is 50 × 7.64 = 382 oz or 382 ÷ 16 = about 24 lbs per 10,000 gallons  pH of water will not change much – 0.2 pH and TA – 5.0 ppm usually no adjustment needed

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Sodium tetraborate pentahydrate

 Adding 9.0 oz per 10,000 gallons is 1.0 ppm boron (B) so 50 ppm is 50 × 9.0 = 450 oz or 450 ÷ 16 = about 28 lbs per 10,000 gallons  pH is 9.2 so it will raise pH of water to near 9.0  Raises total alkalinity by 115 ppm  Need 1.6 fl oz of muriatic acid per 1 oz of sodium tetraborate pentahydrate or 450 ÷ 1.6 = fl oz or 281 ÷ 128 = 2.2 gallons of muriatic acid per 10,000 gallons per 50 ppm borate – this will make pH 7.5 and TA 90 ppm

Borax

 Borax (not Boraxo) – sodium tetraborate decahydrate – 20 Mule Team Borax  Adding 11.785 oz per 10,000 gallons is 1.0 ppm boron (B) so 50 ppm is 50 × 11.785 = 589.25 oz or 589.25 ÷ 16 = about 37 lbs per 10,000 gallons  pH is 9.2 so it will raise pH of water to 9.0  Raises total alkalinity by 115 ppm  Need 2.1 fl oz of muriatic acid per 1 oz of borax or 590 ÷ 2.1 = 281 fl oz or 281 ÷ 128 = 2.2 gallons of muriatic acid per 10,000 gallons per 50 ppm borate – this will make pH 7.5 and TA 90 ppm

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DOT (Disodium Octaborate Tetrahydrate)

 DOT – disodium octaborate tetrahydrate  Adding 6.35 oz per 10,000 gallons is 1.0 ppm boron (B) so 50 ppm is 50 × 6.35 = 317.5 oz or 317.5 ÷ 16 = about 19.8 lbs per 10,000 gallons  pH is 8.6 so it will raise pH of water to 8.6  Need 2.291 fl oz of muriatic acid per 1 oz of DOT or 317.5 ÷ 2.291 = 138.6 fl oz or 138.6 ÷ 128 = 1.1 gallons of muriatic acid per 10,000 gallons per 50 ppm borate – this will make pH 7.5 and TA 90 ppm

Adding Borates to Pool Water 1. Test water for metals – add sequestrant if needed or use a metal pre-filter 2. TA less than 140 ppm, Hardness less than 400 ppm and pH less than 7.4 3. Broadcast about ½ dose into pool with pump running 4. Brush any powder on the pool floor 5. Add ½ of the muriatic acid dose near returns 6. Broadcast final borate dose into pool 7. Brush any powder on the pool floor

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Adding Borates to Pool Water

9. Wait at least 12 hours or next day to test pH and TA 10. Adjust TA to 90 ppm by calculating acid dose then aerate and cause turbulence to increase pH Acid dose is 2.56 fl oz of muriatic acid (31.4%) for 1.0 ppm decrease in alkalinity per 10,000 gallons or use Pool Acid Dose Calc 2.56 fl oz × (Pool Gallons/10,000) × ppm alkalinity decrease

Adding Boric Acid to Pool Water 1. Calculate dose 2. Broadcast ½ dose into water with pump on 3. Brush any powder that is on the pool floor 4. Broadcast second half of dose into water 5. Wait at least 12 hours then test pH and alkalinity 6. Aerate and cause turbulence if pH is below 7.3

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Borate  Add 50 ppm (or 70 ppm with SWG) once check after large water loss  Test strips are sold by LaMotte, ITS, Hach and Taylor  Pool stores in California sell borate products – legal since August 2017  Borate (boron) toxicity is max 50 ppm with LOC (level of concern) of 1.5  Human would need to drink 26 gallons of pool water a day; dogs are 4 times more sensitive so 6 gallons for a dog  You can buy borax and wash your clothes in it and boric acid is used in eye drops, nail fungus remedies, ear drops and wound care  Do not confuse Borate with Bromate. Bromates cause cancer.

Borate Doses, Changes to Water

This chart is a free Tech Bulletin available at www.pcti. online

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Borate Bulletins Available FREE These PCTI Tech Bulletins are available for FREE as a PDF download from: www.pcti.online

Predicting if Water is Balanced, Corrosive or Scale Forming

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Langelier Saturation Index (LSI)

 Based on calcium carbonate saturation  LSI is a mathematical equation to predict the tendency of water to form scale

푖표푛푖푧푎푡푖표푛 1412.5 푆퐼 = 푝퐻 −11.677×푙표푔 퐶퐻푝푝푚 + 푙표푔 퐶.퐴푙푘푝푝푚 −2.56× − + 4.7375 1+1.65× 퐼표푛푖푧푎푡푖표푛 푇푒푚푝 퐾°

NOTE: If you keep the water conditions at the suggested Target levels, you will not need to

11 use or calculate the Saturation Index.

Other Indices

 Ryzner Stability Index (RSI)  Puckorius Scaling Index (PSI)  Hamilton Index (HI)  Calcium Carbonate-Precipitation Potential (CCPP)  Calcite Saturation Index (CSI)

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Original LSI Uses These Water Test Values

 pH  Calcium Hardness  Total Alkalinity  Total Dissolved Solids  Temperature

Calcium Hardness is the Basis for LSI

 Need calcium and magnesium  Minimum is 150 ppm  Target for plaster pools – 350 ppm  Target for vinyl, fiberglass, acrylic etc. – 250 ppm

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New LSI Uses 6 or 7 Water Conditions

 pH  Calcium Hardness (CH) Borate use  Total Alkalinity (TA) requires an adjustment  CYA (new) to LSI also  Temperature  TDS

Factors Are Used in an Equation for Calculation SI = pH + CHF + (TA – (CYA × pHF)) + TF – TDSF Saturation pH as Calcium (Total Alkalinity minus Temperature TDS Index tested Hardness (CYA x pH Factor)) Factor Factor Factor

The goal is to have an LSI equal to 0.00 but – 0.30 to + 0.50 is acceptable Please note that no factors are used for Borate in this calculation.

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Determining the LSI Step 1

1. Test water and record results

Determining LSI Step 2 - Look Up Tables TA CYA CH Temp TDS ppm ppm ppm F° (C°) ppm FACTOR pH-FACTOR FACTOR FACTOR FACTOR 5 = 0.7 6.8 = 0.19 25 = 1.0 32 (0°C) = 0.0 100 = 12.10 25 = 1.4 7.0 = 0.23 50 = 1.3 37 (3°C) = 0.1 500 = 12.14 50 = 1.7 7.2 = 0.27 63 = 1.4 46 (8°C) = 0.2 950 = 12.19 63 = 1.8 7.4 = 0.31 75 = 1.5 53 (12°) = 0.3 1500 = 12.24 72 = 1.9 7.5 = 0.32 100 = 1.6 60 (16°C) = 0.4 2500 = 12.29 96 = 2.0 7.6 = 0.33 124 = 1.7 66 (19°C) = 0.5 3000 = 12.35 124 = 2.1 7.8 = 0.35 150 = 1.8 76 (24°C) = 0.6 4000 = 12.41 146 = 2.2 7.9 = 0.36 200 = 1.9 84 (29°C) = 0.7 5000 = 12.44 194 = 2.3 8.0 = 0.36 246 = 2.0 94 (29°C) = 0.8 246 = 2.4 Multiply CYA ppm 300 = 2.1 105 (41°C) = 0.9 300 = 2.5 by Factor and 400 = 2.2 13 400 = 2.6 subtract from TA ppm 800 = 2.5

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Determining LSI Step 3 – Equation Input

SI = pH + CHF + (TA –(CYA × pHF)) + TF – TDSF Saturation pH as Calcium (Total Alkalinity minus (CYA × pH factor)) Temperature TDS Index tested Hardness Factor Factor Factor

Please note that no factors are used for Borate in this calculation.

Determining LSI Step 4 - Calculate SI = pH + CHF+ (TA –(CYA × pHF)) + TF – TDSF Example: Test Results Factors pH 7.50 (used as is, no factor) 7.50 Calcium 300 ppm +2.1 T. Alk. 100 ppm – 48 ppm* = 52 ppm +1.7 (2.0 if 100 ppm) Temp 80°F +0.65 Sub Total +11.95 TDS 1200 ppm –12.20 CYA 150 ppm LSI = – 0.25 (+ 0.05 if 100 ppm) 14 *(CYA Adjustment 150 ppm × 0.32 = 48 ppm)

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Borate Adjustment Table for 50 ppm

pH Adjustment to Total Alkalinity You can see at higher 7.0 0 pH the adjustment to 7.2 -3 7.4 -4 total alkalinity is 7.5 -6 greater. This shows 7.6 -7 that borate prevents 7.8 -11 8.0 -17 the pH from 8.2 -25 increasing. 8.4 -38 8.5 -46

LSI with CYA and Borate SI = pH + CHF + (TA – ((CYA × pHF) – (BF)) + TF – TDSF Example: Test Results Factors pH 7.50 (used as is, no factor) 7.50 Calcium 300 ppm +2.1 T. Alk. 100 ppm – 48 ppm* – 6 ppm = 46 ppm +1.7 (2.0 if using 100 ppm) Temp 80°F +0.7 Sub Total +11.95 TDS 1200 ppm –12.20 CYA 90 ppm LSI = – 0.25 *(CYA Adjustment 150 ppm × 0.32 = 48 ppm) (If using 100 ppm T. Alk +0.05) **Borate Adjustment pH 7.5 BF = – 6 ppm This is complicated and involves many calculations If using NPC LSI App SI would be – 0.32

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Tables versus NPC LSI

This is the real calculation with adjustments for CYA and

If no adjustments were made for Borate CYA and Borate, the LSI would appear to be balanced (+ 0.05) when it is corrosive (– 0.32)

App for LSI Calculation  Input Name and Water Conditions  See LSI calculation result  Background color changes  Saves records by date  Search records by name  Send records to PC as .XLS file  No recommendations for chem additions  Does not try to sell you anything  Has adjustment for borate One-time purchase for $4.99

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Raising pH Without Changing Alkalinity

CO2 in air and water are in equilibrium Equilibrium

Equilibrium

Aeration causes

CO2 to leave the water (off gas) 18

Aeration Raises pH

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Creating Aeration and Turbulence

9 Possible pH-alkalinity Combinations

pH Alkalinity Chemicals to Add or Action Low Low Add soda ash Low OK Aerate and create turbulence –pH goes up, no change in Alkalinity Low High Add acid to lower Alkalinity then aerate to raise only pH OK Low Add sodium bicarb to raise only Alkalinity OK OK Relax,water is balanced OK High Add acid to lower Alkalinitythen aerate to raise only pH High Low Unusual. Add bicarb to raise Alkalinity then add acid to lower both then aerate High OK Add bicarb to raise Alkalinity then add acid to lower both then aerate High High Add acid to lower boththen aerate to raise only pH

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Acid Column and Walking Acid is a Myth

NO MATTER HOW YOU ADD ACID, THE RESULT IS THE SAME – IT LOWERS pH AND ALKALINITY  Adding acid lowers BOTH pH and TA but not at the same rate because pH is logarithmic and TA in linear

Old Method #1 of Adjusting Water Balance

 Problem high pH and Alkalinity  Add a 1 or 2 quarts of acid, wait for mixing and retest to see what it did  If pH now OK, Alkalinity will be high  Add more acid to lower TA and pH goes even lower  If Alkalinity now OK, the pH is low  Add soda ash to raise pH but TA goes up  Doesn’t work

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Old Method #2 of Adjusting Water Balance

 Perform an Acid Demand Test  Count drops, look up drops used and gallons in pool in Table to figure out acid dose  Makes pH 7.5, who knows what Alkalinity is?  Add more acid then add soda ash and get mad  This Yo-Yo or See-Saw is not the way to go

New Method of Adjusting Water Balance

 Add enough acid to lower Alkalinity to 90 ppm and aerate to raise pH only  Calculate acid dose

2.56 fl oz muriatic acid per 10,000 gallons lowers TA by 1.0 ppm

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Calculating Acid Dose

1. Subtract 90 ppm from current TA to get Decrease ppm 2. Divide pool gallons by 10,000 gallons to get Gallon Factor 3. Multiply 25.6 fl oz × Gallon Factor × ppm decrease

Calculating Acid Dose Example

15,000 Gallon pool with alkalinity of 160 ppm 1. 160 ppm – 90 ppm = 70 ppm Decrease ppm 2. 15,000 ÷ 10,000 = 1.5 Gallon Factor 3. 25.6 fl oz × 70 ppm × 1.5 = 268.8 fl oz 4. 268.8 fl oz ÷ 128 fl oz/gal = 2.1 gallons

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Add Acid Dose and Aerate

 Adding 2.1 gallons of acid to 15,000 gallons lowers TA from 160 to 90 ppm  New pH will be 6.4 – very low (I calculated this)  Now aerate and cause turbulence and pH will go up  Stop aeration when pH is 7.5 – 1-2 hours or a day  Perfect water balance (pH 7.5 and TA of 90 ppm) in hours or a day

Bicarb and Soda Ash Changes

 Sodium Bicarb – 1 lb in 10,000 gallons raises TA by 7.1 ppm  Raises pH by only 0.03  Soda Ash – 1 lb in 10,000 gallons raises TA by 11.3 ppm  Raises pH by 0.3 when pH is 7.0  Raises pH by 0.5 when pH is 7.2  Raises pH by 0.85 when pH is 7.4

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Muriatic Acid (31.4%) Changes

 Muriatic Acid – 25.6 fl oz in 10,000 gallons lowers TA by 10 ppm  Lowers pH by 0.5 when pH is 8.0 and TA is 160 ppm  Lowers pH by 0.4 when pH is 7.8 and TA is 160 ppm  Lowers pH by 0.3 when pH is 7.6 and TA is 160 ppm

Remember, Total Alkalinity and CYA are buffers that prevent pH decreases so high TA and CYA require more acid to lower pH

Pool Acid Dose App – Get Exact Amount  Input Pool Gallons or Liters 15000  Select US Imperial or Metric  Input Current pH 7.8  Input CYA 50  Input Borate 0  Input Current Alkalinity 140  Input Desired pH 6.5 (Change this until New Alk is near 90)  See Acid Dose Amounts= 201.5and New Alkalinity = 88  If CYA is 100 ppm, acid dose is 226.2 and Borate 50 ppm, 251.2  One-time purchase - $5.99, No ads, No in-app purchase  Free version of this App at www.lowrycg.com/pool-acid-dose-calculator/and www.pcti.online

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App to Know How Much of Any Chemical to Add  Input Pool Gallons or Liters  Select US Imperial or Metric  Select Item to Change from 11 Items  Input Desired ppm change  See Amounts for all chemicals that will make the Desired Change  38 Chemicals in data base  Generic by chemical name – No advertisements, no in-app sales  One-time purchase - $5.99

More pH and Alkalinity Adjusting Tricks

 Add dose of acid pouring around perimeter  Aim returns up  Turn on fountains and water features  Use a Venturi jet on return or submersible  Use compressor with manifold with holes

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App for Draining  Input Condition in Pool Water – 600 ppm  Input Target for Condition or Desired Level – 350 ppm  Input Fill or Source Water Condition Level – 150 ppm  Read Drain Percent – 56% of average depth  Read Drain Fraction – 5/9 of average depth  One-time purchase - $2.99, No ads, No in-app purchase

Adjust Water Conditions to Targets and Not for Saturation Index Balance

pH 7.4, TA 80 ppm, CYA 150 ppm, CH 350 ppm, TDS 950 ppm, Temp 80° the LSI = -0.46 Raising TA to 140 ppm gives LSI = -0.01 BUT pH will be unstable and continually go up because high TA raises pH even with borate AND CYA 150 ppm requires free chlorine of 11.25 ppm or with borate 7.5 ppm Better to lower CYA to 50 ppm, raise pH to 7.5, raise TA to 90 ppm and add 50 ppm borate – very stable

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EASY CHEMICAL DOSAGE CHARTS PER 10,000 GALLONS

2.0 to 4.0 PPM Free Chlorine May NOT Work

 APSP (PHTA) Guideline recommendation 2.0 to 4.0 ppm  Level of HOCl needed to kill algae is only 0.05 ppm (Algae are harder to kill than bacteria)  At 30 ppm CYA, 97% of chlorine bound to CYA  ONLY 3% available to kill algae and bacteria

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CHLORINE IN WATER REACTIONS

Cl2 + H2O  HOCl + HCl chlorine + water yields hypochlorous acid + hydrochloric acid HOCl  H+ + OCl– hypochlorous acid dissociates into hydrogen ion + hypochlorite ion Result of chlorine added to water is HOCl + OCl–

HOCl and OCl–

 HOCl is killing form of chlorine  OCl– is a poor disinfectant

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Effect of pH on HOCl and OCl–

Acceptable pH range per APSP

Need 0.05 PPM HOCl TO KILL ALGAE

 Level of HOCl needed to kill algae is only 0.05 ppm (Algae are harder to kill than bacteria)  30 ppm CYA, 97% of chlorine bound to CYA  ONLY 3% available to kill algae and bacteria

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ONLY 3% of chlorine is available and At pH 7.5 there is 50% HOCl and 50% OCl–  Only 1.5% of Free Chlorine as HOCl – Need 0.05 ppm

not enough FC  2.0 ppm of Free Chlorine × 1.5% = 0.030 ppm HOCl to kill algae

maybe enough  3.0 ppm of Free Chlorine × 1.5% = 0.045 ppm HOCl FC to kill algae

 4.0 ppm of Free Chlorine × 1.5% = ppm HOCl Sufficient FC to KILL algae

3% of Chlorine not bound to CYA is in Equilibrium

 As unbound chlorine (the 3%) is used, it is immediately replaced from the chlorine bound to CYA  Bound chlorine is a reservoir for unbound chlorine  As some of 3% is used, it is replaced until there is no more chlorine in the water

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Equilibrium of Bound and Unbound Chlorine

The percentages of 97% and 3% is maintained until all chlorine is used. This is called equilibrium.

Free Chlorine Must be 7.5% of CYA

 THE MINIMUM LEVEL OF FREE CHLORINE IS 7.5% OF CYA  Example: 50 ppm CYA × .075 = 3.75 ppm  80 ppm CYA × .075 = 6.0 ppm  EPA says maximum is 4.0 ppm for people  If CYA is never more than 50 ppm, you will not need more than 4.0 ppm FC  Minimum CYA 20 ppm – need 10 ppm for each 1 ppm FC

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Borate Changes FC Requirement to 5%

 Borate is a pH buffer – use 50 ppm  Borate is also an algaestat  Borate lowers free chlorine minimum from 7.5% to 5.0% !!  Even 100 ppm CYA would need only 5.0 ppm FC But EPA Max is 4.0 ppm  With borate 5% of 80 ppm CYA is 4.0 ppm

There are 4 Generic Calculator Apps that Will Make Your Job Easier

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Take Aways

 Targets conditions are better than PHTA Guidelines  Use aeration and turbulence to balance raise pH in pool  CYA and Total Alkalinity are pH buffers to prevent pH decreases  Borate is a buffer to prevent pH rise

Take Aways (continued)

 Liquid chlorine does not raise pH  CYA should not be more than 50 ppm (min 20 ppm)  CYA builds up quickly in pools using trichlor  Chlorine level should be 7.5% of CYA  Chlorine level should be 5% of CYA if using borate

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