Pool chemistry might seem complicated, but it's actually quite simple once you understand the basics. Think of your pool as a delicate ecosystem that needs three key elements in perfect balance: pH, alkalinity, and chlorine.

pH: The Foundation of Water Balance

What is pH?

pH measures how acidic or basic your pool water is on a scale of 0-14. The "p" stands for "potential" and "H" for hydrogen ions. Here's what the numbers mean:

• 0-6.9: Acidic (corrosive to equipment and irritating to skin)
• 7.0: Neutral (pure water)
• 7.1-14: Basic/Alkaline (reduces chlorine effectiveness)
• 7.4-7.6: Perfect for pools (matches human eye pH)

Why pH Matters

Proper pH is crucial because it affects:

Low pH (Below 7.2)

• Burning eyes and skin
• Equipment corrosion
• Etching of pool surfaces
• Chlorine works too aggressively
• Metal staining

High pH (Above 7.8)

• Cloudy water
• Reduced chlorine effectiveness
• Scale formation
• Filter clogging
• Skin and eye irritation

How to Adjust pH

pH Adjustment Guide:

To Lower pH: Add muriatic acid1 qt per 10,000 gal = -0.2 pH

To Raise pH: Add sodium carbonate1.5 lbs per 10,000 gal = +0.2 pH

Total Alkalinity: The pH Buffer

What is Total Alkalinity?

Total Alkalinity (TA) measures your water's ability to resist pH changes. Think of it as a shock absorber for pH fluctuations. It's measured in parts per million (ppm).

Why Alkalinity Matters

Proper alkalinity (80-120 ppm) acts as a buffer:

• Too Low (Below 80 ppm): pH bounces wildly, equipment corrosion, etching
• Too High (Above 120 ppm): pH is hard to adjust, cloudy water, scale formation
• Just Right (80-120 ppm): Stable pH, clear water, protected equipment

💡 Pro Tip:

Always adjust alkalinity BEFORE adjusting pH. Alkalinity is the foundation that keeps pH stable. If you adjust pH first, it will just bounce back to where alkalinity wants it to be.

How to Adjust Alkalinity

Alkalinity Adjustment Guide:

To Lower TA: Add muriatic acid1 qt per 10,000 gal = -10 ppm

To Raise TA: Add sodium bicarbonate1.5 lbs per 10,000 gal = +10 ppm

Free Chlorine: Your Pool's Sanitizer

Understanding Chlorine Types

Not all chlorine is the same. Here's what you need to know:

• Free Chlorine: Active sanitizer that kills bacteria and algae
• Combined Chlorine: Used-up chlorine bound to contaminants (causes chlorine smell)
• Total Chlorine: Free + Combined chlorine

⚠️ Important:

That strong "chlorine smell" actually means you need MORE chlorine, not less. The smell comes from chloramines (combined chlorine), which form when there isn't enough free chlorine to do the job.

Free Chlorine Levels

Free Chlorine Guidelines:

Minimum:1.0 ppm (barely sanitized)

Ideal Range:3.0-7.0 ppm (perfect)

Shock Level:10+ ppm (treatment only)

Too High:15+ ppm (wait before swimming)

Factors That Affect Chlorine

Several factors consume or reduce chlorine effectiveness:

• Sunlight: UV rays break down chlorine (use stabilizer/cyanuric acid)
• High pH: Reduces chlorine effectiveness by 50% at pH 8.0+
• Bather Load: More swimmers = more contaminants to sanitize
• Organic Matter: Leaves, debris, and algae consume chlorine
• Temperature: Warmer water needs more chlorine

Testing Your Water

Testing Methods

Test Strips

Pros: Quick, easy, multiple tests

Cons: Less accurate, expire quickly

Best for: Daily testing, beginners

Liquid Test Kit

Pros: Very accurate, long-lasting

Cons: Takes longer, more steps

Best for: Precise adjustments, pros

When to Test

• pH & Chlorine: 2-3 times per week minimum
• Alkalinity: Weekly (more stable than pH)
• After Heavy Use: Always test after pool parties
• After Rain: Weather affects chemistry
• Before Adding Chemicals: Never guess

The Order of Operations

Chemical adjustments must be done in the correct order for best results:

🎯 Correct Adjustment Sequence

Adjust Total Alkalinity first (80-120 ppm)

Then adjust pH (7.4-7.6)

Finally maintain chlorine (3-7 ppm)

Common Mistakes to Avoid

❌ Adjusting pH Before Alkalinity

This is like trying to paint over rust. The pH will just bounce back because alkalinity controls pH stability.

❌ Adding Too Much at Once

Make small adjustments and wait 4-6 hours between doses. Pool chemistry changes gradually.

❌ Testing at the Wrong Time

Test when the pump has been running for at least 2 hours to ensure proper circulation and mixing.

Quick Reference: Chemical Dosing

Chemical Dosing Chart (per 10,000 gallons)

pH Adjustments:

• Lower pH: 1 qt muriatic acid = -0.2
• Raise pH: 1.5 lbs soda ash = +0.2

Alkalinity Adjustments:

• Lower TA: 1 qt muriatic acid = -10 ppm
• Raise TA: 1.5 lbs baking soda = +10 ppm

Chlorine Additions:

• 1 lb cal-hypo shock = +10 ppm
• 1 gal liquid chlorine = +10 ppm

Safety Notes:

• Never mix chemicals directly
• Add chemicals to water, not vice versa

✅ Mastery Checklist

You've mastered pool chemistry when you can:

✓ Test water accurately using strips or liquid kits
✓ Adjust alkalinity before pH every time
✓ Maintain 3-7 ppm free chlorine consistently
✓ Keep pH stable between 7.4-7.6
✓ Calculate proper chemical doses for your pool size
✓ Recognize when water is properly balanced

🎯 Ideal Pool Chemistry Ranges