Water Chemistry
25%of exam
Equipment
20%of exam
Operations
20%of exam
Safety
20%of exam
Spa Operation
15%of exam
Quick Facts
- Credential
- CPO
- Owner
- PHTA
- Format
- Instructor course
- Exam
- Open-book MCQ
- Pass
- 75%
- Validity
- 5 years
- Prereq
- No experience
- Core skill
- Operate safely
Chlorine Formula
Free plus combined equals total.
FCCCTCTC=FC+CC
Free vs Combined
Free
- Kills germs
- Active residual
- Maintain level
Combined
- Chloramines
- Odor/irritation
- Oxidize away
Available vs spent
Chemical Picker
- pH low→Soda ash(Raise pH)
- pH high→Acid(Lower pH)
- TA low→Bicarb(Raise buffer)
- Calcium low→Calcium chloride
- Outdoor chlorine loss→CYA(Stabilizer)
- Combined chlorine high→Breakpoint dose
- Algae present→Shock/brush/filter
- Scale forming→Lower LSI
Water Balance
- pH
- Acid/base strength
- Target pH
- 7.2-7.8
- Low pH
- Corrosion/irritation
- High pH
- Scale/cloudiness
- Alkalinity
- pH buffer
- Low TA
- pH bounce
- High TA
- pH drift
- Calcium
- Hardness control
Balance Triad
pH moves; alkalinity steadies; calcium protects.
pHTACHLSI
pH vs Alkalinity
pH
- Current acidity
- Chlorine strength
- Comfort impact
Alkalinity
- pH buffer
- Stability control
- Prevents bounce
Now vs buffer
Sanitizers
- Free chlorine
- Active sanitizer
- Combined chlorine
- Used chlorine
- Total chlorine
- FC plus CC
- Bromine
- Hot-water sanitizer
- HOCl
- Strong chlorine
- OCl-
- Weak chlorine
- ORP
- Oxidizing potential
- CYA
- Chlorine stabilizer
Shock vs Sanitize
Shock
- Temporary boost
- Oxidizes waste
- Corrective action
Sanitize
- Continuous residual
- Kills pathogens
- Routine control
Correct vs maintain
Chlorine Math
- TC formula
- FC plus CC
- CC formula
- TC minus FC
- Breakpoint
- About 10x CC
- Superchlorinate
- Oxidize contaminants
- Shock
- Raise sanitizer
- Demand
- Sanitizer consumed
- Residual
- Sanitizer remaining
- ppm
- mg/L equivalent
LSI
- LSI
- Balance index
- Negative LSI
- Corrosive tendency
- Positive LSI
- Scaling tendency
- Temperature
- Raises LSI
- Calcium
- Raises LSI
- Alkalinity
- Raises LSI
- TDS
- Dissolved solids
- Saturation
- Balanced water
Flow Path
Pool to pump to filter.
SkimmerPumpFilterReturn
Sand vs Cartridge
Sand
- Backwash cleaning
- Rugged media
- Higher water use
Cartridge
- Remove/rinse
- No backwash
- More surface area
Backwash vs rinse
Filter Picker
- Need simple rugged→Sand
- Need easy service→Cartridge
- Need finest capture→DE
- Pressure rises→Clean filter
- Sand/DE dirty→Backwash
- Cartridge dirty→Remove/rinse
Circulation
- Pump
- Moves water
- Strainer
- Catches debris
- Skimmer
- Surface removal
- Main drain
- Bottom suction
- Return inlet
- Water reentry
- Flow rate
- Gallons per minute
- Turnover
- Volume recirculated
- Head loss
- Flow resistance
Pump vs Filter
Pump
- Moves water
- Creates flow
- Needs prime
Filter
- Removes particles
- Needs cleaning
- Shows pressure
Flow vs clarity
Filters
- Sand
- Durable media
- Cartridge
- Removable element
- DE
- Fine filtration
- Backwash
- Reverse-clean filter
- Pressure rise
- Dirty filter clue
- Filter aid
- Improves capture
- Channeling
- Sand flow path
- Air relief
- Bleeds trapped air
Feeders
- Erosion feeder
- Tablet dissolver
- Liquid feeder
- Solution pump
- Peristaltic
- Tube pump
- Cal-hypo
- Raises calcium
- Trichlor
- Adds CYA
- CO2
- Lowers pH
- Acid feed
- pH control
- Interlock
- Flow-based shutdown
Code vs Handbook
Local code
- Legal minimum
- AHJ enforced
- Facility-specific
Handbook
- Training reference
- Best practices
- Exam source
Law beats guide
Closure Picker
- Cannot see bottom→Close pool
- Sanitizer too low→Close/correct
- pH outside code→Correct before open
- Fecal incident→Contamination plan
- Drain cover missing→Close immediately
- Equipment unsafe→Close/repair
Testing + Records
- DPD
- Chlorine test
- Phenol red
- pH test
- Titration
- Drop-count test
- Calibration
- Meter accuracy
- Sample point
- Representative water
- Daily log
- Required record
- Corrective action
- Document response
- Local code
- Authority rules
Troubleshooting
- Cloudy water
- Filter/chemistry issue
- Green water
- Algae growth
- Chlorine odor
- Chloramines
- Foam
- Organics/surfactants
- Scale
- High LSI
- Etching
- Low LSI
- Low flow
- Restriction/air leak
- High pressure
- Dirty filter
Safety First
No clarity, no cover, no opening.
ClarityDrainChemicalElectrical
Safety Picker
- Chemical splash→Flush water
- Chlorine gas→Evacuate area
- Entrapment risk→Disable pump
- Electrical fault→Keep out
- Slip hazard→Barricade/repair
- Emergency call→Posted phone
Safety Risks
- VGB
- Drain-cover law
- Entrapment
- Suction hazard
- Evisceration
- Severe suction injury
- Diving risk
- Depth hazard
- Electrical
- Shock hazard
- Slip/fall
- Deck hazard
- Chemical burn
- Exposure injury
- RWI
- Waterborne illness
Chemical Safety
- SDS
- Hazard details
- PPE
- Personal protection
- Ventilation
- Fume control
- Dry storage
- Moisture prevention
- Separate acids
- Prevent gas
- Separate chlorine
- Prevent reaction
- Add chemical
- To water
- Spill plan
- Emergency response
Spa Speed
Hot small water changes fast.
HeatAerationLoadDemand
Spa vs Pool
Spa
- Hot water
- Small volume
- High demand
Pool
- Larger volume
- Slower change
- Lower temperature
Fast vs slower
Spa + Hot Tub
- Max temp
- 104 F
- Hot water
- Faster chemistry
- Aeration
- Raises pH
- Small volume
- Rapid change
- High load
- High demand
- Biofilm
- Hidden growth
- Drain/refill
- TDS control
- Legionella
- Hot-water risk
Common Traps
Chlorine Odor
Too much chlorine ≠ Often chloramines
CYA Role
Sanitizer ≠ Stabilizer only
Filter Role
Kills pathogens ≠ Removes particles
pH Trap
High pH helps chlorine ≠ High pH weakens chlorine
Backwash Trap
Cleans cartridges ≠ Cleans sand/DE
Spa Trap
Same as pool ≠ Changes faster
Code Trap
Handbook overrides code ≠ Local code governs
Last Minute
- 1.TC = FC plus CC
- 2.CC = TC minus FC
- 3.Breakpoint about 10x CC
- 4.pH target 7.2-7.8
- 5.Alkalinity buffers pH
- 6.CYA protects outdoor chlorine
- 7.Filter removes particles only
- 8.Pump creates circulation flow
- 9.Cloudy bottom means close
- 10.VGB covers prevent entrapment
- 11.Never mix acid/chlorine
- 12.Spa chemistry changes faster
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