Introduction
Clean, clear, and safe pool water requires proper chemical management. Whether operating a commercial hotel pool, water park, or residential pool, understanding the role of each treatment chemical is essential for swimmer comfort, equipment protection, and regulatory compliance. This guide covers all major pool water treatment chemicals with dosing guidance.
Core Pool Water Parameters
| Parameter | Ideal Range | Test Frequency | Why It Matters |
|---|---|---|---|
| Free chlorine | 1.0-3.0 mg/L (commercial: 2.0-4.0) | Daily (commercial: 2-4x/day) | Primary disinfection — kills bacteria and viruses |
| Combined chlorine | 0-0.4 mg/L (ideally 0) | Daily | Indicates chlorine demand from contaminants |
| pH | 7.2-7.8 (ideal: 7.4-7.6) | Daily (commercial: 2-4x/day) | Chlorine efficacy, swimmer comfort, corrosion control |
| Total alkalinity | 80-120 mg/L as CaCO3 | Weekly | pH buffer — prevents pH bounce |
| Calcium hardness | 200-400 mg/L | Weekly | Water balance — prevents scaling or corrosion |
| Cyanuric acid (CYA/stabilizer) | 30-50 mg/L (outdoor), 0 (indoor) | Monthly | Protects chlorine from UV degradation |
| TDS | <1500 mg/L above source water | Monthly | High TDS reduces chlorine efficacy |
| Turbidity | <0.5 NTU (ideal <0.2) | Daily visual, weekly meter | Water clarity for swimmer safety |
Primary Pool Treatment Chemicals
1. Sanitizers / Disinfectants
Calcium Hypochlorite (Cal-Hypo) — 65-70% Available Chlorine
- Form: White granules or tablets (1″ or 3″)
- Dosage: 28-85g per 10,000 gallons to raise FC by 1 mg/L (depends on % chlorine)
- Pros: Low cost, adds calcium (useful in soft water), stable in storage
- Cons: Raises pH (pH ~11 in solution), adds calcium (problem in hard water areas), requires pre-dissolving
- Best for: Routine chlorination, shock treatment
Sodium Dichlor — 56-62% Available Chlorine
- Form: White granules, fast dissolving
- Dosage: 32-70g per 10,000 gallons to raise FC by 1 mg/L
- Pros: Near-neutral pH (6.5-7.0), adds CYA (stabilizer), dissolves quickly
- Cons: More expensive per kg of available chlorine, accumulates CYA over time
- Best for: Routine chlorination, cyanuric acid maintenance
Trichlor — 90% Available Chlorine
- Form: Slow-dissolve tablets (1″ or 3″), sticks
- Dosage: Via automatic feeder or floating dispenser
- Pros: Highest chlorine content, slow-dissolve for continuous dosing, adds CYA
- Cons: Very acidic (pH ~3), can over-stabilize pool (CYA build-up), not for skimmer use (damages equipment)
- Best for: Continuous chlorination via erosion feeder
Liquid Chlorine (Sodium Hypochlorite) — 10-12.5%
- Form: Liquid solution
- Dosage: 0.3-0.8L per 10,000 gallons to raise FC by 1 mg/L (at 12.5%)
- Pros: No CYA, no calcium, immediate action
- Cons: Short shelf life (degrades ~30% in 90 days at 25°C), high pH (~13), heavy (water weight)
- Best for: Commercial pools with automatic liquid feed systems
2. pH Adjusters
pH Increaser — Sodium Carbonate (Soda Ash)
- Form: White powder or granules
- Dosage: ~170g per 10,000 gallons to raise pH by 0.2
- Application: Pre-dissolve in bucket of pool water, distribute around perimeter with pump running
pH Reducer — Sodium Bisulfate (Dry Acid)
- Form: White granules
- Dosage: ~250g per 10,000 gallons to lower pH by 0.2
- Application: Pre-dissolve, distribute around deep end. Never add acid through skimmer.
3. Total Alkalinity Adjuster — Sodium Bicarbonate
- Dosage: ~680g per 10,000 gallons to raise TA by 10 mg/L
- Application: Broadcast across deep end with pump running. Do not add with acid or calcium.
4. Calcium Hardness Increaser — Calcium Chloride
- Dosage: ~550g per 10,000 gallons to raise CH by 10 mg/L
- Application: Pre-dissolve in bucket, distribute around perimeter. Don’t add on same day as soda ash or bicarb.
5. Stabilizer / Conditioner — Cyanuric Acid (CYA)
- Dosage: ~370g per 10,000 gallons to raise CYA by 10 mg/L
- Application: Add to skimmer (dissolves slowly) or dissolve in warm water in bucket. Do not backwash for 48 hours.
- Warning: CYA above 100 mg/L significantly reduces chlorine efficacy (“chlorine lock”). If CYA is high, partial drain and refill is the only practical correction.
6. Algaecides
- Quaternary ammonium compounds (Quats): 150-300mL per 10,000 gallons weekly. Foam potential in spas and water features.
- Polyquats: 150-300mL per 10,000 gallons weekly. Non-foaming, better for spas and commercial pools.
- Copper-based: 30-90mL per 10,000 gallons. Effective against most algae but can cause staining at high pH. Not for pools with soft vinyl liners.
- Sodium bromide: Activates with chlorine shock to form bromine — effective for yellow/mustard algae.
7. Clarifiers and Flocculants
PAC (Poly Aluminium Chloride) for Pools
- Form: Liquid (~10% Al2O3) or powder
- Dosage: 5-20 mg/L (powder) — 50-200g per 10,000 gallons
- How it works: Coagulates fine suspended particles (dead algae, body oils, sunscreen, dust) into filterable flocs
- Application: Dilute 1:10 with pool water, distribute around perimeter. Run pump 8-12 hours. Backwash filter after treatment.
- Advantage vs alum: Works over wider pH range, less pH depression, less sludge, faster floc formation
Pool Gel Clarifiers (Polymer-based)
- Dosage: 30-60mL per 10,000 gallons weekly
- How it works: Cationic polymer droplets coat filter media fibers/sand grains, improving capture of fine particles
- Best for: Routine maintenance, polishing water clarity
8. Shock Treatment Chemicals
Calcium Hypochlorite Shock
- Dosage: 450-900g per 10,000 gallons (breakpoint chlorination: 10x combined chlorine level)
- Best for: Heavy bather loads, after rain storms, algae treatment, combined chlorine removal
Potassium Monopersulfate (Non-Chlorine Shock)
- Dosage: 450-900g per 10,000 gallons
- Pros: Oxidizes contaminants without raising chlorine, swim immediately after treatment
- Cons: Does not sanitize — must maintain chlorine residual separately. Interferes with DPD chlorine testing.
- Best for: Indoor pools, spas, routine oxidation maintenance
Commercial Pool Regulatory Notes
Commercial and public pool chemical dosing is regulated by local health authorities. Key requirements vary by country:
- USA: CDC Model Aquatic Health Code (MAHC) — free chlorine 2-10 mg/L, pH 7.2-7.8, automated chemical controllers recommended
- EU: DIN 19643 (Germany) — free chlorine 0.3-0.6 mg/L (lower due to activated carbon filtration + ozone)
- UK: PWTAG guidelines — free chlorine 0.5-1.0 mg/L (indoor), 1.0-3.0 mg/L (outdoor)
- UAE: Dubai Municipality — free chlorine 1.0-2.0 mg/L, pH 7.2-7.8, CYA max 100 mg/L
Chemical Storage and Safety
- NEVER mix different chlorine types — can cause fire or explosion
- NEVER mix chlorine with acid — releases toxic chlorine gas
- Store chlorine products in cool, dry, ventilated area away from hydrocarbons (oils, greases, solvents)
- Cal-hypo is a strong oxidizer — keep away from rags, paper, metal tools (spontaneous combustion risk with organic materials)
- Always add chemicals to water, not water to chemicals
- Wear PPE: chemical-resistant gloves, safety glasses, dust mask when handling powders
HydroChemix supplies bulk swimming pool treatment chemicals for commercial pool operators, water parks, hotels, and resorts. Products include PAC (liquid and powder), calcium hypochlorite, sodium bicarbonate, sodium carbonate, and custom chemical packages. Contact jingshuicc@gmail.com for commercial pricing and chemical procurement planning for your facility.