A quick overview of basic water chemistry terms and facts.

1. Week1 :
Basic Water Chemistry

2. The prime concern of pool
and Spa Professionals:
spa professionals
Is to maintain sanitary pool and
spa water.
[the growth of bacteria
and algae must be controlled]

3. In addition to water
chemistry other important factors
include:
• Water circulation
• Filtration,
• Physical maintenance practices

4. Bather Protection
Parameters:
Water treatment chemicals are added
to pool and
spa water to affect one or more of three
general
areas

5. Bather Protection
Parameters:
• To protect swimmers and bathers against disease
and infection.
• To protect pool surfaces and equipment against corrosive
and/or scale forming water.
• To produce water that is sparkling clear so
that it is aesthetically pleasing and inviting to
swimmers and bathers.

6. Bather Protection
Parameters:
The
most effective way to control bacteria
and algae
is to properly maintain sanitizer level,
pH, water
clarity and temperature.

7. 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

8. 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.

9. Sanitizing: Chlorine
Most 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)

10. 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

11. 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

12. 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

13. 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)

14. Sanitizers: Biguanide
● When a biguanide sanitizer is used in pool or spa
water the ideal level should be continuously maintained
between 30 and 50 ppm.

15. 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]

16. 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].

17. Temperature
High 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

18. Calcium Hardness
The 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

19. TDS
The 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.

20. Oxidation
Sold 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.

21. Shocking &
Superchlorination
Shocking = 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.

22. 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)?

23. Chapter 8-3!

24. Metals
Dissolved 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

25. 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*

26. 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.]

27. 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

28. 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*

29. Effect of Cyanuric Acid on
the TA Test
CYA 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*

30. Cyanuric Correction Factor:
*Typically a factor of 33% (0.33) is used*
pH FACTOR
7.0 0.23
7.2 0.27
7.4 0.31
7.6 0.33
7.8 0.35
8.0 0.36

31. How to Correct TA
2 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

32. 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.

33. LSI Conversion Factors

34. TDS Factors for LSI
TDS in ppm Factor Used
0 - 1000 12.1
1000 - 2000 12.2
2000+ 12.3

35. 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

36. 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

37. 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)

38. Corrosion & Flow Rate
Many factors contribute to corrosion on wetted
surfaces, these include (not are not limited to):
• aggressive water [low pH, TA and calcium
hardness]
• high halogen levels [Cl and Br]
• dissolved gasses [especially with well water]
• high mineral content [TDS, leads to high electrical
conductivity]
• high water temperature
• high flow velocities
• turbulent flow
• galvanic corrosion [when 2 dissimilar metals
are in contact]

39. 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

40. 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]

41. Hamilton Index
3 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

42. Hamilton Index Chart

43. 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]

44. 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

45. Why pH increases in Spas
2 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]

46. 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

47. Bather Load and pH in Spas
High 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

48. 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]

49. 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

50. Spa Surfaces & pH
● Plaster surfaces typically increase pH [highly alkaline
nature of plaster]
● Redwood hot tubs typically decrease pH [by adding
acidic materials]

51. 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

52. 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]

53. 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

54. 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

55. Sanitizers in Depth
Most 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

56. 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

57. 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

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

59. Sanitizers in Depth
FAC = 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

61. 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