How much chlorine do I add to my pool?

For regular maintenance, add 10 oz of liquid chlorine (10%) per 10,000 gallons to raise free chlorine by approximately 1 ppm. For shock treatment, use 1 lb of granular shock (65% calcium hypochlorite) per 10,000 gallons. Always test and adjust based on current readings.

What is the ideal pool water balance?

Ideal ranges: Free Chlorine 1–3 ppm, pH 7.2–7.6, Total Alkalinity 80–120 ppm, Cyanuric Acid 30–50 ppm, Calcium Hardness 200–400 ppm. The Langelier Saturation Index (LSI) should be between -0.3 and +0.3 for balanced water.

How much pH Up do I need?

To raise pH by 0.2 units, add approximately 6 oz of sodium carbonate (pH Up) per 10,000 gallons. Broadcast over the water with the pump running. Retest after 4 hours before adding more.

What is the Langelier Saturation Index?

The LSI measures whether pool water is balanced, corrosive, or scale-forming. It combines pH, temperature, calcium hardness, total alkalinity, and TDS. An LSI of -0.3 to +0.3 is balanced; below -0.3 is corrosive (etches plaster); above +0.3 causes calcium scale deposits.

Pool Chemical Dosing Calculator

Calculate exact chemical doses for chlorine, pH, alkalinity, CYA, and calcium hardness — with Langelier Saturation Index water balance

Pool & Water Readings

Pool Volume (gallons)

Don't know your volume? Use the Pool Volume Calculator →

Water Temperature (°F)

Current Water Readings

Free Chlorine (ppm)

Target: 1.0–3.0 ppm

Target: 7.2–7.6

Total Alkalinity (ppm)

Target: 80–120 ppm

Cyanuric Acid / Stabilizer (ppm)

Target: 30–50 ppm

Calcium Hardness (ppm)

Target: 200–400 ppm

Chlorine Product Preference

Langelier Saturation Index 0.00 Balanced

Corrosive Balanced Scaling

Dosing Rates Reference

Standard doses per 10,000 gallons of pool water. Always test water before and after treatment.

Chemical	Active %	Dose per 10k gal	Effect	Wait Time
Liquid Chlorine	10%	10 oz	Raises FC ~1 ppm	4 hrs
Granular Shock (Cal-Hypo)	65%	1 lb	Raises FC ~6 ppm (shock dose)	8 hrs / overnight
Trichlor Tabs (3")	90%	1 tab / week	Slow-release FC maintenance	Continuous
pH Up (Sodium Carbonate)	100%	6 oz	Raises pH ~0.2	4 hrs
pH Down (Muriatic Acid 31.45%)	31.45%	16 fl oz	Lowers pH ~0.2	4 hrs
Alkalinity Up (Sodium Bicarb)	100%	1.5 lb	Raises TA ~10 ppm	6 hrs
Cyanuric Acid (Stabilizer)	100%	1 lb	Raises CYA ~10 ppm	24 hrs (skimmer)
Calcium Chloride (Hardness Up)	77–80%	1.25 lb	Raises CH ~10 ppm	4 hrs

Safety Rules

⚠

Never Mix Chemicals

Never combine pool chemicals directly — chlorine + acid produces toxic chlorine gas. Add each chemical separately with pump running and allow full circulation between additions.

⚠

Add Chemical to Water

Always add chemicals to water, never water to chemicals. Pre-dissolve granular products in a bucket of pool water before broadcasting.

🔒

Protective Equipment

Wear chemical-resistant gloves and eye protection when handling pool chemicals. Store in a cool, dry, ventilated area away from direct sunlight and heat sources.

🕑

Dosing Intervals

Never add more than one chemical at a time. Wait at least 15–30 minutes (and ideally 1–4 hours) between different chemical additions. Retest after each addition.

💡

Add at Dusk or Sunrise

Add chlorine at dusk or early morning to reduce UV degradation. Unstabilized chlorine loses 50–90% of its potency within hours of sunlight exposure.

💡

Pump On During Treatment

Run the circulation pump for at least 4–8 hours after adding chemicals to ensure even distribution throughout the pool volume.

Weekly Maintenance Schedule

Daily

Check free chlorine (target 1–3 ppm)
Check pH (target 7.2–7.6)
Run pump minimum 8 hours
Skim surface debris

Weekly

Test all 5 parameters
Brush pool walls and floor
Vacuum pool
Clean skimmer and pump baskets
Shock if combined chlorine > 0.5 ppm
Add algaecide (preventive)

Monthly

Test calcium hardness
Test cyanuric acid level
Backwash or clean filter
Check and clean pool light
Inspect fittings and gaskets

Seasonally

Opening: super-chlorinate to 10 ppm
Opening: verify all equipment
Closing: lower water level
Closing: add algaecide & winter shock
Closing: blow out and plug lines

Common Pool Chemicals

Chemical Name	Common Brand Names	Active Ingredient	Use For
Liquid Chlorine	Pool Shock (liquid), Clorox Pool	Sodium hypochlorite 10–12%	Regular chlorination
Granular Shock	HTH Shock, BioGuard Burn Out	Calcium hypochlorite 65–78%	Shocking, algae treatment
Trichlor Tabs	Clorox, HTH, BioGuard	Trichloroisocyanuric acid 90%	Slow-release maintenance
pH Up	Arm & Hammer pH Up, HTH	Sodium carbonate (soda ash)	Raise pH
pH Down / Dry Acid	Arch Chemicals, Natural Chemistry	Sodium bisulfate or muriatic acid	Lower pH & alkalinity
Alkalinity Up	HTH, BioGuard Balance Pak 100	Sodium bicarbonate (baking soda)	Raise total alkalinity
Stabilizer / Conditioner	HTH Stabilizer, BioGuard	Cyanuric acid 100%	Protect chlorine from UV
Calcium Hardness Up	HTH Hardness Up, BioGuard	Calcium chloride 77%	Raise calcium hardness

LSI Calculator

The Langelier Saturation Index (LSI) measures whether your water is corrosive, balanced, or scale-forming. Values between −0.3 and +0.3 are considered balanced.

LSI = pH + TF + CF + AF − 12.1

pH (from Tab 1) 7.40

Temperature Factor (TF) 0.60

Calcium Factor (CF) 2.18

Alkalinity Factor (AF) 2.00

TDS Constant 12.10

LSI Result 0.08

✅

Balanced

Water is properly balanced. No corrosion or scaling risk.

Temperature Factor (TF) Table

Temperature (°F)	Temperature (°C)	TF Value
32°F	0°C	0.0
41°F	5°C	0.07
50°F	10°C	0.14
59°F	15°C	0.20
68°F	20°C	0.31
77°F	25°C	0.40
86°F	30°C	0.50
95°F	35°C	0.56
104°F	40°C	0.60

Seasonal Tips

🌸 Opening Your Pool

Remove and clean cover; check for damage
Reconnect pump, filter, and heater
Fill to proper water level
Run pump 24 hrs to circulate
Test all 5 parameters
Super-chlorinate to 10 ppm
Adjust pH, alkalinity, and calcium
Add stabilizer if CYA < 30 ppm
Brush and vacuum after 24 hrs

🍁 Closing Your Pool

Test and balance all parameters
Shock with double dose
Add winterizing algaecide
Lower water below return jets
Blow out all plumbing lines
Add antifreeze to lines if freezing climate
Remove and store accessories
Cover pool securely
Protect pump and equipment

How to Use This Calculator

Enter Pool Volume

Type your pool's volume in gallons. If you don't know it, use our Pool Volume Calculator first.

Enter Water Test Results

Input your current test strip or test kit readings for chlorine, pH, alkalinity, CYA, and calcium hardness.

Read Your Dosing Plan

The calculator shows which parameters need adjustment and the exact amount of each chemical to add.

Add Chemicals One at a Time

Add each chemical separately with the pump running. Wait the recommended time, then retest before adding more.

Dosing Formulas

Chlorine Dose

ppm needed × gallons / 10,000 × dose rate

pH Adjustment

Δ pH / 0.2 × 6 oz per 10k gal (pH Up)

Alkalinity Dose

Δ ppm / 10 × 1.5 lb per 10k gal (bicarb)

LSI Formula

pH + TF(temp) + CF(calcium) + AF(alk) − 12.1

CYA Dose

Δ ppm / 10 × 1.0 lb per 10k gal

Calcium Dose

Δ ppm / 10 × 1.25 lb per 10k gal

Key Terms

Free Chlorine (FC)

The active, sanitizing form of chlorine available to kill bacteria and algae. Distinguished from combined chlorine (chloramines), which is ineffective and causes eye irritation.

Total Alkalinity (TA)

The water's ability to resist pH changes (buffering capacity). Low TA causes pH to swing rapidly; high TA makes pH difficult to adjust. Measured in ppm of bicarbonate.

Cyanuric Acid (CYA)

A stabilizer that protects chlorine from UV degradation. Without CYA, sunlight destroys chlorine within hours. Too much CYA (>80 ppm) reduces chlorine effectiveness significantly.

Calcium Hardness (CH)

The concentration of dissolved calcium in pool water. Low CH causes water to leach calcium from pool plaster (corrosive). High CH leads to calcium scale deposits on surfaces and equipment.

LSI (Langelier Saturation Index)

A calculated value combining pH, temperature, calcium hardness, total alkalinity, and TDS to determine if water is corrosive (<-0.3), balanced (-0.3 to +0.3), or scale-forming (>+0.3).

Shocking

Adding a large dose of chlorine (typically 10 ppm or higher) to oxidize combined chlorine, kill algae, and restore water clarity. Also called super-chlorination or oxidizing treatment.

Frequently Asked Questions

How often should I test my pool water?

Test free chlorine and pH at least 2–3 times per week during swim season, daily during heavy use or hot weather. Test total alkalinity, CYA, and calcium hardness monthly. After heavy rain or a pool party, test and adjust before the next swim.

Why won't my chlorine stay up?

Low CYA (stabilizer) is the most common cause — sunlight destroys unstabilized chlorine within hours. Also check for high combined chlorine (chloramines), algae blooms, or heavy bather load. Test CYA and raise to 30–50 ppm if low. If combined chlorine exceeds 0.5 ppm, shock the pool.

Can I add two chemicals at the same time?

No. Never add two pool chemicals at the same time, even separately into the water. Some combinations (like chlorine and acid) produce toxic gases. Add each chemical one at a time, wait for full circulation (15–30 minutes minimum, 4 hours ideally), then retest before adding another.

What happens if my LSI is too low (corrosive water)?

Corrosive water (LSI below -0.3) attacks pool plaster, grout, and metal fittings, causing etching and pitting. It can also dissolve calcium from plaster. Fix by raising pH, increasing calcium hardness, or raising alkalinity. Raising pH is usually the fastest solution.

What happens if my LSI is too high (scaling water)?

Scale-forming water (LSI above +0.3) deposits calcium carbonate on pool surfaces, plumbing, and equipment. This reduces heater efficiency and can clog filters. Fix by lowering pH, reducing alkalinity, or partially draining and refilling to dilute calcium hardness.

How much does it cost to balance pool chemicals?

Monthly chemical costs for a typical 20,000-gallon pool range from $30–$100 depending on your climate, bather load, and local water quality. Unstabilized or out-of-balance water can double costs. Testing regularly and making small, targeted adjustments is far more economical than letting parameters drift far out of range.