Week1 :Basic Water Chemistry

The prime concern of pool and Spa Professionals:spa professionals Is to maintain sanitary pool andspa water.

[the growth of bacteriaand algae must be controlled]

In addition to waterchemistry other important factors include:

• Water circulation• Filtration,• Physical maintenance practices

Bather Protection Parameters:

Water treatment chemicals are added to pool andspa water to affect one or more of three generalareas

Bather Protection Parameters:• To protect swimmers and bathers against diseaseand infection.

• To protect pool surfaces and equipment against corrosiveand/or scale forming water.

• To produce water that is sparkling clear sothat it is aesthetically pleasing and inviting toswimmers and bathers.

Bather Protection Parameters:

Themost effective way to control bacteria and algaeis to properly maintain sanitizer level, pH, waterclarity and temperature.

Sanitizing:

● Sanitizers are the most important parameter in Pools & Spas.

● Defined as reducing the concentration of pathogenic organisms to acceptable levels.

● Added to Pool & Spa water to protect bathers from disease and infection.

● Good sanitation = ensuring measurable active sanitizer residual is maintained at all times.

● Sanitizer levels should be regularly monitored using an appropriate test kit

Sanitizing: Chlorine

● Most widely used sanitizer for Pools & Spas.

● When chlorine is added to Pool water, Free Available Chlorine (FAC) is formed.

● FAC should be continuously maintained between 1.0 - 3.0 ppm

● Combined Chlorine should never exceed 0.2ppm, ideally 0.0ppm

● Combined Chlorine = difference between the measured total available chlorine and the free available chlorine.

Sanitizing: ChlorineMost common forms of Chlorine (alphabetically):

• Cal Hypo (Calcium hypochlorite)

• Dichlor (Dichloro-s-triazinetrione)

• Gas chlorine (elemental chlorine)

• Lithium Hypochlorite

• Liquid chlorine or bleach (Sodium hypochlorite,10-15% chlorine solution)

• Trichlor (Trichloro-s-triazinetrione)

Sanitizing: Chlorine

● All forms of chlorine produce Hypochlorous Acid (HOCl) and Hypochlorite Ion (OCl-) when dissolved in water.

● Together, HOCl and OCl- = free chlorine residual

Sanitizing: Combined Chlorine

● Chlorine combines with nitrogen containing organic matter to form combined chlorine.

● Combined chlorine is also known as Chloramines

● FAC is consumed during this process

● Chloramines are much less effective as sanitizers than free chlorine

● Chloramines can produce strong odors, as well as eye and skin irritation

● Chloramines are very difficult to destroy

Sanitizers: Stabilized Chlorine

● Stabilized chlorine is an organic stabilized form of chlorine using Cyanuric Acid

● TriChlor and Dichlor = cyanuric acid with a few chlorine molecules added.

● TriChlor = cyanuric acid with 3 chlorine molecules (hence 'Tri'Chlor)

● DiChlor = cyanuric acid with 2 chlorine molecules (hence 'Di'Chlor)

● When dissolved in water, Trichlor and Dichlor create hypochlorus acid and cyanuric acid

● Cyanuric acid stabilizes and protects free chlorine residuals from sunlight-induced decomposition

Sanitizers: Bromine

● When Bromine is added to water, it created hypobromous acid

● Bromamines are formed when hypobromous acid is combined with nitrogen based compounds.

● Total bromine is the combination of measurable free bromine and bromamines

● Total bromine is used as a measurement for effective sanitizer residual as bromamines still have a very great sanitizing property, unlike chloramines

● Total Bromine should be maintained in Pools & Spas between 4.0 - 6.0 ppm (no less than 2.0, no more than 10.0ppm)

Sanitizers: Biguanide

● When a biguanide sanitizer is used in pool or spawater the ideal level should be continuously maintainedbetween 30 and 50 ppm.

pH

Balanced pH maximizes the effectiveness of sanitizers and oxidizers.

Best ranges for pH = 7.4 - 7.6 (no less than 7.2, no more than 7.8)

pH also affects swimmer comfort if outside of these ranges.

Above 7.8, pH is less effective at killing bacteria and algae.

Below 7.2, pH becomes acidic, especially when combined with low TA.

To raise pH, add Sodium Carbonate [soda ash]. this is not the same as Sodium Bicarbonate [baking soda]

To lower pH, add Acid [Muriatic]

Total Alkalinity

Total Alkalinity is the 'buffering capacity' of water.

Ability to resist rapid changes in pH.

A proper level of TA allows for easy adjustment of pH.

Adjust TA before adjusting pH.

Recommended levels for TA = 80-120ppm [as CACO3] - depending on the type of sanitizer

Low TA can lead to 'pH Bounce', allowing the pH to fluctuate widely whenever small amounts of acidic or basic chemicals are introduced.

Increase TA by adding Sodium Bicarbonate [NaHCO3].

Decrease TA by adding Acid [pH will need to be adjusted after this step].

TemperatureHigh temperatures can lead to calcium becoming less soluble [forming calcium carbonates].

Gasses become less soluble, causing evaporation or 'Gas Off'.

Evaporation leads to Carbon Dioxide leaving the water, resulting in a raise in pH.

Typical pool temperature = 78 - 82 F

Typical Spa temperature = no more than 104 F

Calcium HardnessThe measure of Calcium Ions [Ca+2], expressed as calcium carbonate [CACO3]

Low calcium [soft water], leads to water dissolving calcium from other areas (pool liners, etc.) causing pitting, corroding.

High calcium [hard water, supersaturated], = cloudy water, calcium deposits onto pool liners and circulating equipment (especially heating elements).

Typical calcium hardness levels in pools = 150 - 1,000ppm [as CaCO3]

Typical calcium hardness levels in spas = 150 - 800ppm [as Caco3]

Ideal range in both pools and spas = 200 - 400ppm [as CaCO3]

To raise Ca, add calcium [calcium chloride]

Ca is not easily lowered, adjust TA and pH accordingly to prevent supersaturation

TDSThe measure of all dissolved matter in water

Increase of TDS = accumulation of impurities during course of operation.

High TDS = hazy water, corrosion of fixtures, inhibits sanitation.

The lower the TDS, the better

To lower TDS, drain and fill with water that has a lower TDS than the pool water.

TDS should never go above 1,500ppm greater than the startup TDS

Startup TDS = Fill water + salt, start up chemicals, etc.

OxidationSold as shock

Oxidation supports sanitation

Removes contaminants (such as bather waste)

lowers sanitizer demand

removes combined chlorine

improves water clarity

some forms of Oxidation = Potassium Monopersulfate, Chlorine products, Ozone.

Shocking & SuperchlorinationShocking = adding large concentrations of oxidizing chemicals to drive a chemical reaction.

Corrective shocking = kill algae, remove organics and chloramines, clear up cloudy water.

Preventative shocking = frequently adding sufficient oxidizing chemicals to prevent the growth of algae, increase in chloramines, etc. before these items become a problem.

Some oxidizing products = Chlorine, Potassium Monopersulfate, Hydrogen Peroxide.

Which Chemical to Shock with?Things to know:

● Type of sanitizer used in pool● Reason, purpose for shocking

Hydrogen Peroxide = Biguanide [kills Chlorine & Bromine]

Chlorine = Chlorine and Bromine

Potassium Monopersulfate = Chlorine and Bromine

When Chloramines = 0.2ppm+, shocking is done by raising the FAC level 10x the chloramine level

Question: FC = 1.5ppm / TC = 2.5ppm

1) how much is the FAC needed to be raised by in ppm?2) how much shock is need to be added to the pool (in ppm)?

Chapter 8-3!

MetalsDissolved metals are present in all common water sources

Concentrations of dissolved metals can vary widely from regions, to communities.

Metals cause staining on pool surfaces.

Colors of pool water from metal concentrations:

● Brown● Blue● Green● Grey● Black

Different metals and their colours:Manganese: Black-Brown-Purple cast [typically not noticed until addition of Chlorine or pH is raised]

Copper: Light blue or green cast [when dissolved / in solution]. Turquoise or black [when oxidized / precipitated]. *Causes hair to turn green in some cases*

Iron: Clear green / cloudy yellow to rust brown [when oxidized / precipitated] *typically found in water taken from wells or rivers*

Metal levels / Removal:*ANSI / NSPI standard recommends: 0 ppm of all metals in

pool water.*

Metals under 1.00ppm:● Typically stay in solution [not yet precipitated / oxidized]● removed by chelating or sequestering agent combined with a filter

Metals over 1.00ppm:● Typically precipitate / fall out of solution.● removed by adding sequestering agent combined with a filter.

[Note: older pools with copper piping can erode due to high velocity of water flow, causing copper to enter the pool water & cause staining / casting.]

Advanced Water Balance:

This section will expand on the following:

● pH/TA measuring & adjusting

● Effects of CYA on TA test results

● LSI [Langelier Saturation Index]

● Hamilton Index

● Hot Water Chemistry

pH & Total Alkalinity Testing:TA testing is the same for pools and spas

Typical kits use: bromocresol green-methyl red as end point indicator. [Green - red colour development] *Interference with CYA*

Other indicators: methyl orange [Yellow - orange colour development, Chlorine can bleach indicator] *Interference with CYA*

Our eXact method uses: Alizarin Red S + Citrate [yellow - orange colour development] *NO Interference with CYA*

Effect of Cyanuric Acid on the TA TestCYA in water can contribute to certain test kits’ TA readings. [Higher readings]

CYA is a weak buffering agent.

Happens when TriChlor or DiChlor is used as sanitizer.

When calculating LSI, the true carbonate alkalinity is used. [must calculate CYA percentage contributing the TA reading 1st].

The percentage of CYA adjustment varies with pH. [pH test are typically done when calculating CYA effect on TA]

*Typically a factor of 33% (0.33) is used*

Cyanuric Correction Factor:

*Typically a factor of 33% (0.33) is used*

pH FACTOR7.0 0.23

7.2 0.27

7.4 0.31

7.6 0.33

7.8 0.35

8.0 0.36

How to Correct TA2 step method is used (when CYA is present)

1. Measure TA and CYA

2. multiply CYA by factor adjustment

3. Subtract factored CYA result from TA result.

Example:

1. TA = 120ppm CYA = 40ppm [pH = 7.6]

2. 40ppm x 0.33 = 13.2ppm

3. 120 - 13.2 = 106.8ppm

TRUE carbonate alkalinity = 106.8ppm

Langelier Saturation Index

Langelier Saturation Index

Langlier Saturation Index (LSI)Saturation Index (SI) = A value that indicates if a Pool / Spa is balanced or not.

To calculate SI, measure:

● pH ● *Temperature ● *Calcium Hardness● *Total Alkalinity● **TDS

*pH is the only parameter that does not have a conversion factor.

**TDS is the only parameter that has a conversion factor but does not have a conversion table.

LSI Conversion Factors

TDS Factors for LSI

TDS in ppm Factor Used0 - 1000 12.1

1000 - 2000 12.2

2000+ 12.3

Langlier Saturation Index (LSI)

SI = pH + TF + CF + AF - 12.1*

● Acceptable SI value = -0.3 to +0.5

● Ideal SI value = 0.0 to +0.5

● Balanced water = 0.0

*Please note: even though SI might = -0.3 to +0.5, balance might be difficult to maintain if one or more of these parameters are outside of the recommended concentration range.*

The following slide is an example of this

LSI Example

pH = 7.0

Temperature = 84F

Calcium Hardness = 75ppm

Total Alkalinity = 1,100ppm

TDS = 750ppm

SI = 7.0 +0.7 + 3.0 1.5 - 12.1

SI = 0.0

LSI Example (Cont’d)

Although SI says the water is balanced:

● Low pH & Calcium Hardness = Corrosive water

● High Total Alkalinity = Over buffered pH (difficult to edit pH)

Corrosion & Flow RateMany factors contribute to corrosion on wetted surfaces, these include (not are not limited to):

• aggressive water [low pH, TA and calciumhardness]• high halogen levels [Cl and Br]• dissolved gasses [especially with well water]• high mineral content [TDS, leads to high electricalconductivity]• high water temperature• high flow velocities• turbulent flow• galvanic corrosion [when 2 dissimilar metalsare in contact]

Water Velocity

Higher velocity of water can lead to:

● Erosion-Corrosion [defined: Degradation of material surface due to mechanical action]

● Impingement-Corrosion [defined: Form of erosion-corrosion associated with fluid against a solid surface]

NSPI recommended max water velocity of:

● Suction Piping @ 8 FPS● Pressure Piping @ 10FPS

Hamilton Index

● Who: Jacques Hamilton [CA pool tech]

● What: 3 Step procedure to achieve water balance

● When: early 70’s

● Why: Stick it to Langelier [LSI developed for municipal water, edited by P&S adapters so much that it didn’t work any more - Hamiltons 2 cents]

Hamilton Index3 Step Approach:

1: Test TOTAL HARDNESS [NOT Calcium Hardness] and derive Total Alkalinity level from chart

2: Adjust Total Alkalinity as indicated on chart

3: Adjust & maintain pH levels between 7.8 - 8.2

Hamilton Index Chart

Hot Water Chemistry & Water Balance in Spas

pH & TA:

Difficult to control due to:

● High temperature [rapid loss of CO2]

● Aeration [jets and air blowers]

● Higher bather load [more bather:water volume ratio]

Hot Water Chemistry & Water Balance in Spas

Typically:

● pH raises [CO2 leaving Pool]

● Acid only lowers pH temporarily

● Too much acid = loss of buffering capacity [LOW TA]

pH to drop too low too quickly very difficult to get pH in control

Why pH increases in Spas2 factors:

1: dissolved gasses become less soluble as temp increases

2: Carbon Dioxide [CO2] as Carbonic Acid [H2CO3] = lower pH.

*HOWEVER high temps & air jets= CO2 leaving water.*[This = reduced acid concentration, thus raising pH]

Without Carbonic Acid, bicarbonates can not can not control pH raising. [typically raising to 8.2-8.4pH]

Why pH increases in Spas

High pH & Temp = bicarbonates to convert to carbonates [loss of CO2 & H20]

The result [CaCO3] =

● Scaling● Cloudy Water● Clogged Heaters● Rough Spa Surface● Discolored Spa Surface

NOTE: pH will change, TA will not

Bather Load and pH in SpasHigh bather load = lowering of pH [usually]

why: perspiration & other slightly acidic materials

Where: not so much in residential [lower bather load] more so in commercial [higher bather load] = consistently low pH, pH increasers needed

pH & Sanitizers in Spas

Low pH sanitizers can decrease spa water pH.

Low pH Sanitizers:

● TriChlor tabs = 2.9pH● Bromine tabs = 4.0pH● Non-Chlorine MPS shock = low pH [not defined]

pH & Sanitizers in Spas

High pH sanitizers can increase spa water pH.

High pH Sanitizers:

● Lithium Hypochlorite = 10.7 pH● Cal Hypo = 10.8pH● Sodium Hypochlorite = >12pH

*less effective:Granular DiChlor = 6.0pH

Biguanide = 5.5pH

Spa Surfaces & pH

● Plaster surfaces typically increase pH [highly alkaline nature of plaster]

● Redwood hot tubs typically decrease pH [by adding acidic materials]

TA Buffering Agents Using Phosphates [H2PO4-/HPO4-]

Phosphate buffers can be useful [depending on application]

PROS:● Loss of CO2 does not affect Phosphate buffers

● Phosphate buffers lower @ 7.2 - 7.5pH

● Bicarbonate buffers higher @ 7.8 - 8.2pH

TA Buffering Agents Using Phosphates [H2PO4-/HPO4-]

CONS:● Phosphates + Calcium = Calcium phosphate [cloudy water]

● If fill water is high in Ca, Ca increase is used = Cloudy water

● Adding Phosphates decreases Ca levels

● Ca increaser can not be added [cloudy water if added]

● low Ca can damage plaster pool surfaces

● Phosphates can add to algae production [mostly in outdoor pools]

Water Hardness in Spas

Calcium carbonate = ‘the hard-water’ mineral

dissolves as: Calcium ions & Carbonate ions [until water is fully saturated]

Warmer water needs less ppm to be ‘fully saturated’

Fully saturated = additional Calcium ions + Carbonate ions [calcium carbonate precipitate].

*Scale is more of a problem for hot water [spas] than cold water [pools]

SI is used to determine proper balance of Ca with:● Temperature● pH● Total Alkalinity

How to Raise Calcium Hardness (in Spa Water)

Add Hydrated Calcium Chloride [77% typically]

1 tbsp per 100 gal = 25 ppm increase in Ca

if pH & TA are balanced, Ca = 200 - 400 ppm

Sanitizers in DepthMost used sanitizer for Pool & Spa = Chlorine based sanitizers

Registered by EPA:

● Chlorine● Bromine● Biguanide● Silver

Periodic Table of Elements = table of all known elements divided into families

Halogen family:

● Fluorine● Chlorine● Bromine● Iodine● Astatine

Sanitizers in Depth

Many theories as to how Cl and Br act on microorganisms

These halogens are great for killing:

● Bacteria● Algae● Disease-causing organisms

Common types of Chlorine for P&S:

● Trichloro-s-Triazinetrione [TriChlor]● Sodium Hypochlorite [Bleach & Liquid Chlorine]● Calcium Hypochlorite [CalHypo]● Sodium Dichloro-s-Triazinetrione [DiChlor]● Elemental Chlorine [Chlorine Gas]● Lithium Hypochlorite

*list is based on popularity of use, summer 2000

Sanitizers in Depth

FAC = Hypochlorous Acid & Hypochlorite ion HOCl + OCl- & CyaCl

*Cl associated with CYA is released as HCl & HOCl on demand

HOCl is a more effective biocide than OCl-

Concentration of HOCl vs OCl- is determined by water pH

Sanitizers in DepthHOCl ‘breaks up’ into a hydrogen ion [H+] & a hypochloride ion [OCl-] according to the following equation:

Sanitizers in DepthFAC = Hypochlorous Acid & Hypochlorite ion

HOCl + OCl- & CyaCl

At 6.0pH, HOCl starts turning into OCl-

The higher the pH, the more HOCl turns [and stays] into OCl-

To keep Cl most active, pH should be no higher than 7.8pH [7.4 - 7.6pH is ideal]

pH below 7.2 jeopardizes water balance & bather comfort

Sanitizers in Depth

All Chlorine sanitizers have the same characteristics:

● Strong bactericides & algaecides

● Provide residual FAC to kill disease-causing organisms

● Act as a sanitizer, algicide, and/or shock product [not including tablets]

● proper application destroys contaminants found mainly in sweat, urine & windblown debris

● Solid forms have good shelf life & easily stored

● Solid forms with low pH can damage liners and siding if coming in contact at high concentrations