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How to raise free chlorine in your pool

Doses checked 11/10/2026

Add chlorine to bring free chlorine up to the target for your stabilizer reading: at least 2 ppm, or about 7.5% of your stabilizer if that is higher, but never above 4 ppm, the swimming level on most labels we checked. The share comes from industry guidance (a pool chemical maker and a trade magazine). The calculator works out how much of your product to add.

Your pool and readings
Pool size

The volume of water in your pool. In UK gallons? UK gallons x 1.2 = US gallons.

Checked on every build: 82 tests of the sums this calculator runs, including 8 amounts printed in published charts, labels and manuals (ours must match them, or land under them where we start low on purpose) and 23 tests of its limits: caps, smaller rounds, and the cases where it gives no amount.

The target goes up with stabilizer

  1. Stabilizer 0 ppm2 ppm
  2. Stabilizer 10 ppm2 ppm
  3. Stabilizer 20 ppm2 ppm
  4. Stabilizer 30 ppm2.5 ppm
  5. Stabilizer 40 ppm3 ppm
  6. Stabilizer 50 ppm4 ppm
  7. Stabilizer 60 ppm4 ppm (capped: 7.5% would be 4.5)
  8. Stabilizer 70 ppm4 ppm (capped: 7.5% would be 5.25)
Free chlorine the calculator aims for at each stabilizer reading: the larger of 2 ppm and about 7.5% of the stabilizer (industry guidance from a pool chemical maker and a trade magazine), rounded up to the next half ppm, and never above 4 ppm, the swimming level on most chlorine labels we checked. Where the share would be higher, the calculator says the stabilizer is too high and points you to a pool professional. Bars are drawn to scale out of 4 ppm.

One pool chemical maker says You could go higher, but you would also need to proportionally increase your free chlorine levels ... to maintain 7.5% of your CYA level in free chlorine. and a trade magazine gives the same share: As an example, you add 30 ppm of CYA and you will always need about 2 ppm of free chlorine (30 ppm × .075 = 2.25 ppm). The Oregon Health Authority says Exceeding the CYA to free chlorine ratio of 45:1 means the chlorine is unable to kill pathogens in the water.

The official minimums are lower. CDC's model code for public pools says AQUATIC VENUES using CYA shall maintain a minimum DPDFC concentration of 2.0 ppm (mg/L). Without stabilizer, its minimum is 1 ppm.

Free, combined and total chlorine

Test kits read free chlorine, and many also read total chlorine. CDC's model code says Combined chlorine is determined by taking the difference between the Total Chlorine (TC) and DPD-FC concentrations. It calls combined chlorine chloramines, and says to reduce the concentration of COMBINED CHLORINE (chloramines) in the water when the concentration exceeds 0.4 ppm (mg/L).

If free chlorine is low and combined chlorine is above 0.4 ppm, use the shock calculator instead: it checks your free chlorine first.

Where official ranges differ

The calculator aims for 2–4 ppm, the band in the Licking County Health Department (Ohio) chart. Other health departments give 1–3 ppm (Arkansas Department of Health) and 2–3 ppm (Maryland Department of Health). Salt system makers differ too: Pentair's manual says 2.0 - 4.0 ppm. Hayward's says chlorine tests will show the desired 1-3ppm free chlorine reading.

Add some, wait, retest

  1. Test free chlorine and stabilizer.
  2. Work out the amount with the calculator above. Tablets dissolve slowly; to raise free chlorine now, use liquid chlorine, cal-hypo or dichlor.
  3. With nobody in the pool and the pump running, add it as your label directs. Never add it through a skimmer, floater or feeder that holds or has held tablets.
  4. Wait at least 4 hours with the pump running, then retest.
  5. Swim only once free chlorine is at or below the level on your product's label.

Questions people ask

How do I raise free chlorine? Add to its target

Add liquid chlorine, cal-hypo or dichlor, worked out for your pool size and product strength, with the pump running. Wait at least 4 hours and retest.

How do I increase free chlorine quickly?

Use liquid chlorine, cal-hypo or dichlor: tablets dissolve slowly.

What's the difference between free and total chlorine?

Total chlorine is free chlorine plus combined chlorine. CDC's model code says Combined chlorine is determined by taking the difference between the Total Chlorine (TC) and DPD-FC concentrations.

What should free chlorine be?

At least 2 ppm, or about 7.5% of your stabilizer reading if that is higher, and no higher than your chlorine label allows for swimming; most labels we checked say 4 ppm.

Why is my free chlorine low when my stabilizer is high?

High stabilizer raises the free chlorine you need. Above about 50 ppm of stabilizer the target would pass the 4 ppm swimming level, so the calculator caps it and points you to a pool professional: stabilizer can only be lowered by draining part of the water.

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The charts behind this page

Show all 28 figures and where each one comes from

Each figure this page and its calculator use. Open one for the source's own words, the other sources we checked it against, and the checks it has been through.

  • Minimum free chlorine, pool with no stabilizer (CYA): 1 ppm Official

    CDC Model Aquatic Health Code, 5th edition (2024), Code Official says: AQUATIC VENUES not using CYA shall maintain a minimum DPD-FC concentration of 1.0 ppm (mg/L). Source page (opens in a new browser tab)

    Also checked: CDC: Home pool and hot tub water treatment and testing Official says: CDC recommends pH 7.0–7.8 and a chlorine concentration of at least 1 ppm in pools and at least 3 ppm in hot tubs. Source page (opens in a new browser tab)

    Also checked: CDC healthy swimming infographic: inspection Official says: The free chlorine concentration should be at least 1 ppm in pools and at least 3 ppm in hot tubs/spas. Source page (opens in a new browser tab)

    Checked against the source on 11/9/2026. Re-opened by a second checker on 11/9/2026, who matched the source's words to this figure. Looked up again on 11/10/2026 by a checker who couldn't see our figure: it came back with the same figure.

  • Minimum free chlorine, pool with stabilizer (CYA) or stabilized chlorine: 2 ppm Official

    CDC Model Aquatic Health Code, 5th edition (2024), Code Official says: AQUATIC VENUES using CYA shall maintain a minimum DPDFC concentration of 2.0 ppm (mg/L). Source page (opens in a new browser tab)

    Also checked: CDC: Home pool and hot tub water treatment and testing Official says: If using cyanuric acid, a chlorine stabilizer, or chlorine products with cyanuric acid (for example, products commonly known as dichlor or trichlor [see product label]), CDC recommends pH 7.0–7.8 and a chlorine concentration of at least 2 ppm in pools. Source page (opens in a new browser tab)

    Also checked: Oregon Health Authority: Fact Sheet 6, Cyanuric Acid Official says: pools using CYA must maintain a minimum chlorine concentration of 2 ppm. Source page (opens in a new browser tab)

    Checked against the source on 11/9/2026. Re-opened by a second checker on 11/9/2026, who matched the source's words to this figure. Looked up again on 11/10/2026 by a checker who couldn't see our figure: it came back with the same figure.

  • Ideal free chlorine range (home pool target band): 2–4 ppm Official

    Licking County Health Department (Ohio): Pool and Spa Water Chemistry Adjustment Guide Official says: Free Chlorine (ppm) 1 2-4 N/A (recommended not higher than 5) Source page (opens in a new browser tab)

    Also checked: Oregon Health Authority: Water Quality Standards, OAR 333-062-1000 (public pools) Official says: Free Chlorine (w/CYA) 2.0ppm 2.0-4.0ppm 10.0ppm Source page (opens in a new browser tab)

    Also checked: Pentair IntelliChlor IC15/20/40/60 Installation and User's Guide, P/N 520589 Rev R Other source says: 2.0 - 4.0 ppm. Source page (opens in a new browser tab)

    Also checked: HTH 3" Chlorine Tabs Advanced product page Other source says: Add one tablet per 10,000 gallons of pool water every week, or as often as needed, to maintain a free available chlorine level of 1–4 ppm. Source page (opens in a new browser tab)

    Also checked: Hayward AquaRite Owner's Manual 092538 RevD Other source says: chlorine tests will show the desired 1-3ppm free chlorine reading. Source page (opens in a new browser tab)

    Also checked: Arkansas Department of Health Official says: Pool* 1.0 1.0 – 3.0 5.0 Source page (opens in a new browser tab)

    Also checked: Maryland Department of Health Official says: Free Chlorine 1.5 ppm 2.0 ppm – 3.0 ppm 10.0 ppm Source page (opens in a new browser tab)

    Checked against the source on 11/10/2026. Re-opened by a second checker on 11/9/2026, who matched the source's words to this figure.

  • Free chlorine above which chlorine labels say do not swim (re-entry level): 4 ppm Other source

    EPA-accepted label: B's Pool Supply Sodium Hypochlorite Solution 12.5% (EPA Reg. 55487-20001) Other source says: SWIMMING POOL WATER DISINFECTION – Do not reenter pool with a chlorine level above 4 ppm for risk of bodily harm. Source page (opens in a new browser tab)

    Also checked: EPA-accepted label: BioGuard Master Calcium Hypochlorite 67% (Bio-Lab, EPA Reg. 5185-238) Other source says: Reentry into treated swimming pool is prohibited above levels of 4 ppm chlorine due to risk of bodily injury. Source page (opens in a new browser tab)

    Also checked: EPA-accepted label: PDQ ChlorSan 8% Sodium Hypochlorite (EPA Reg. 58880-2) Other source says: Reentry into treated pools is prohibited above levels of 4.0 ppm due to risk of bodily harm. Source page (opens in a new browser tab)

    Also checked: HTH Pool Care Shock product page Other source says: Do not enter the pool until free available chlorine levels return to 1–4 ppm. Source page (opens in a new browser tab)

    Also checked: EPA-accepted label: Tarry trichlor 8 oz tablets/sticks (Qualco, EPA Reg. 3525-120) Other source says: Re-entry into treated swimming pools/spas is prohibited above levels of 3.0 ppm. Source page (opens in a new browser tab)

    Also checked: EPA-accepted label: Tarry trichlor 8 oz tablets/sticks (Qualco, EPA Reg. 3525-120) Other source says: Do not enter pool until the chlorine residual drops to 2.0 ppm (parts per million). Source page (opens in a new browser tab)

    Also checked: CDC Model Aquatic Health Code, 5th edition (2024), Code Official says: Maximum DPD-FC concentrations shall not exceed limits specified on the product label. Source page (opens in a new browser tab)

    Checked against the source on 11/9/2026. Re-opened by a second checker on 11/9/2026, who matched the source's words to this figure. Looked up again on 11/10/2026 by a checker who couldn't see our figure: it came back with the same figure.

  • Free chlorine reading above which the test may bleach out (false low): 10 ppm Official

    CDC: Home pool and hot tub water treatment and testing Official says: If the chlorine concentration of the water sampled from the pool or hot tub is more than 10 ppm, the test might partially or totally bleach out, resulting in a false low or 0 ppm chlorine result. Source page (opens in a new browser tab)

    Checked against the source on 11/9/2026. Re-opened by a second checker on 11/9/2026, who matched the source's words to this figure.

  • Free chlorine to keep, as a share of stabilizer (CYA): 7.5% of CYA Other source

    Orenda Technologies: What is the ideal CYA level for a swimming pool? Other source says: You could go higher, but you would also need to proportionally increase your free chlorine levels ... to maintain 7.5% of your CYA level in free chlorine. Source page (opens in a new browser tab)

    Also checked: AQUA Magazine Other source says: The free chlorine level should be 7.5 percent of CYA. Source page (opens in a new browser tab)

    Also checked: AQUA Magazine Other source says: As an example, you add 30 ppm of CYA and you will always need about 2 ppm of free chlorine (30 ppm × .075 = 2.25 ppm). Source page (opens in a new browser tab)

    Also checked: AQUA Magazine Other source says: Or if you have 50 ppm of CYA, you will need about 4 ppm of free chlorine (50 × .075 = 3.75 ppm). Source page (opens in a new browser tab)

    Also checked: Trouble Free Pool forum thread 'Chlorine/CYA chart vs 7.5% of CYA' Other source says: 7.5% is essentially the FC level where chlorine kills algae faster than it can reproduce Source page (opens in a new browser tab)

    Also checked: Oregon Health Authority: Fact Sheet 6, Cyanuric Acid Official says: Exceeding the CYA to free chlorine ratio of 45:1 means the chlorine is unable to kill pathogens in the water. Source page (opens in a new browser tab)

    Checked against the source on 11/9/2026. Re-opened by a second checker on 11/9/2026, who matched the source's words to this figure.

  • Combined chlorine level that calls for action (shock / superchlorinate): 0.4 ppm Official

    CDC Model Aquatic Health Code, 5th edition (2024), Code Official says: reduce the concentration of COMBINED CHLORINE (chloramines) in the water when the concentration exceeds 0.4 ppm (mg/L). Source page (opens in a new browser tab)

    Also checked: Oregon Health Authority: Water Quality Standards, OAR 333-062-1000 (public pools) Official says: Combined Chlorine 0ppm 0ppm 0.4ppm Source page (opens in a new browser tab)

    Also checked: Multnomah County (Oregon) Environmental Health: Water Treatment - Swimming Pools, EHS-0058 Official says: Breakpoint chlorinate when combined chlorine exceeds 0.5 ppm, or when chloramines are first detected. Source page (opens in a new browser tab)

    Checked against the source on 11/9/2026. Re-opened by a second checker on 11/9/2026, who matched the source's words to this figure. Looked up again on 11/10/2026 by a checker who couldn't see our figure: it came back with the same figure.

  • Combined chlorine = total chlorine minus free chlorine: total chlorine minus free chlorine Official

    CDC Model Aquatic Health Code, 5th edition (2024), Code Official says: Combined chlorine is determined by taking the difference between the Total Chlorine (TC) and DPD-FC concentrations. Source page (opens in a new browser tab)

    Checked against the source on 11/9/2026. Re-opened by a second checker on 11/9/2026, who matched the source's words to this figure.

  • Ideal stabilizer (cyanuric acid, CYA): 30–50 ppm Official

    Oregon Health Authority: Fact Sheet 6, Cyanuric Acid Official says: The ideal range for CYA is typically between 30-50 ppm. Source page (opens in a new browser tab)

    Also checked: Licking County Health Department (Ohio): Pool and Spa Water Chemistry Adjustment Guide Official says: Cyanuric Acid (ppm) 0 30-50 70 Source page (opens in a new browser tab)

    Also checked: Orenda Technologies: What is the ideal CYA level for a swimming pool? Other source says: We recommend 30-50 ppm CYA for residential pools. Source page (opens in a new browser tab)

    Also checked: the PHTA pool industry committee Other source says: A certain amount of cyanuric acid (usually within the range of 30 – 50 ppm) is necessary to protect outdoor pools from degradation by sunlight. Source page (opens in a new browser tab)

    Also checked: Pentair IntelliChlor IC15/20/40/60 Installation and User's Guide, P/N 520589 Rev R Other source says: 30 - 50 ppm Source page (opens in a new browser tab)

    Also checked: Arkansas Department of Health Official says: Add CYA separately, only as needed, to maintain 25–40 ppm in outdoor pools. Source page (opens in a new browser tab)

    Also checked: Arkansas Department of Health Official says: Anything above 50ppm CYA is considered high and can interfere with other pool chemicals' effects and equipment. Source page (opens in a new browser tab)

    Also checked: Maryland Department of Health Official says: Cyanuric Acid (if used) 30 ppm 40 ppm- 50 ppm 100 ppm Source page (opens in a new browser tab)

    Checked against the source on 11/10/2026. Re-opened by a second checker on 11/9/2026, who matched the source's words to this figure.

  • Stabilizer (CYA) level above which the tool says 'ask a pool professional': 70 ppm Official

    Licking County Health Department (Ohio): Pool and Spa Water Chemistry Adjustment Guide Official says: Cyanuric Acid (ppm) 0 30-50 70 Source page (opens in a new browser tab)

    Also checked: CDC Model Aquatic Health Code, 5th edition (2024), Code Official says: The CYA concentration at all AQUATIC VENUES shall remain at or below 90 ppm (mg/L). Source page (opens in a new browser tab)

    Also checked: Oregon Health Authority: Fact Sheet 6, Cyanuric Acid Official says: The CYA level at all AQUATIC VENUES shall remain at or below 90 ppm (mg/L). Source page (opens in a new browser tab)

    Also checked: the PHTA pool industry committee Other source says: If the cyanuric acid level exceeds the APSP maximum of 100 ppm, a partial drain and refi ll is recommended. Source page (opens in a new browser tab)

    Also checked: Arkansas Department of Health Official says: The MAHC & ADH recommend that CYA not exceed 90 ppm for standard pools. Source page (opens in a new browser tab)

    Also checked: Maryland Department of Health Official says: Cyanuric Acid (if used) 30 ppm 40 ppm- 50 ppm 100 ppm Source page (opens in a new browser tab)

    Checked against the source on 11/10/2026. Re-opened by a second checker on 11/9/2026, who matched the source's words to this figure.

  • Liquid chlorine (sodium hypochlorite solution): specific gravity (weight of 1 mL in grams) used to turn the label's % by weight into an amount by volume: 1.2 specific gravity (g per mL) Other source (worked out)

    Worked out: 1.195 rounded up to 1.2

    Alliance Chemical (Taylor, Texas): Safety Data Sheet, Sodium Hypochlorite 12.5% Other source says: Relative Density 1.195 at 20/20 °C (water = 1) Source page (opens in a new browser tab)

    Also checked: Alliance Chemical (Taylor, Texas): Safety Data Sheet, Sodium Hypochlorite 12.5% Other source says: Density 1.1929 g/cm³ at 20 °C Source page (opens in a new browser tab)

    Also checked: FPC (fpcusa.com): 10.0% Sodium Hypochlorite product sheet Other source says: Specific Gravity 1.13-1.20 @ 68F/20C Source page (opens in a new browser tab)

    Checked against the source on 11/9/2026.

  • Liquid chlorine: US fl oz to raise free chlorine 1 ppm in 10,000 US gal = 128 / (strength % x 1.2): 128/(strength x 1.2) Other source (worked out)

    Worked out: 1 ppm in 10,000 US gal = 37.85 g of available chlorine (10,000 × 3.785412 L × 1 mg per L, NIST). The label % is by weight (B's label: 12.5% sodium hypochlorite, 'Total available chlorine is 11.9%'), and the liquid weighs about 1.2 g per mL. So 1 mL holds at most strength/100 × 1.2 g of chlorine, and US fl oz per ppm = (3,785.412 ÷ 29.57353) ÷ (strength × 1.2) = 128 ÷ (strength × 1.2). Treating the whole label % as available chlorine (the label shows it is a little lower) keeps the amount on the low side.

    EPA-accepted label: B's Pool Supply Sodium Hypochlorite Solution 12.5% (EPA Reg. 55487-20001) Other source says: Total available chlorine is 11.9% Source page (opens in a new browser tab)

    Also checked: EPA-accepted label: B's Pool Supply Sodium Hypochlorite Solution 12.5% (EPA Reg. 55487-20001) Other source says: ACTIVE INGREDIENT: SODIUM HYPOCHLORITE………….. 12.5% Source page (opens in a new browser tab)

    Also checked: Alliance Chemical (Taylor, Texas): Safety Data Sheet, Sodium Hypochlorite 12.5% Other source says: Concentration 12.5% w/w Source page (opens in a new browser tab)

    Also checked: FPC (fpcusa.com): 10.0% Sodium Hypochlorite product sheet Other source says: Available Cl2 9.5-10.5 wt% ASTM D2022 Source page (opens in a new browser tab)

    Also checked: Alliance Chemical (Taylor, Texas): Safety Data Sheet, Sodium Hypochlorite 12.5% Other source says: Relative Density 1.195 at 20/20 °C (water = 1) Source page (opens in a new browser tab)

    Also checked: Indiana Department of Health: Adjusting Chemical Levels in a Swimming Pool / Water Chemistry Adjustment Guide Official says: Sodium Hypochlorite (12%) 10.7 fl.oz. 1.7 qts 3.3 qts Source page (opens in a new browser tab)

    Also checked: HASA liquid chlorine page Other source says: 12.5 PPM of free chlorine in 10,000 gallons—delivered by a single gallon of HASA’s 12.5% liquid chlorine Source page (opens in a new browser tab)

    Also checked: EPA-accepted label: PDQ ChlorSan 8% Sodium Hypochlorite (EPA Reg. 58880-2) Other source says: 80 to 160 oz. of product for each 10,000 gallons of water Source page (opens in a new browser tab)

    Also checked: EPA-accepted label: B's Pool Supply Sodium Hypochlorite Solution 12.5% (EPA Reg. 55487-20001) Other source says: For a new pool or when opening the pool in the spring, super chlorinate with 52 to 104 fl. oz. of product Source page (opens in a new browser tab)

    Also checked: Salt Lake County Health Department (Utah): pool chemical dosages Official says: Sodium Hypochlorite - Bleach 13 fl. oz. ½ gallon 1 gallon Source page (opens in a new browser tab)

    Also checked: Multnomah County (Oregon) Environmental Health: Water Treatment - Swimming Pools, EHS-0058 Official says: LIQUID 10% 1pt. 1ppm Source page (opens in a new browser tab)

    Checked against the source on 11/9/2026.

  • Liquid chlorine 6%: US fl oz to raise free chlorine 1 ppm in 10,000 US gal: 17.78 US fl oz per ppm per 10,000 US gal Other source (worked out)

    Worked out: 128 ÷ (6 × 1.2) = 17.78

    EPA-accepted label: B's Pool Supply Sodium Hypochlorite Solution 12.5% (EPA Reg. 55487-20001) Other source says: Total available chlorine is 11.9% Source page (opens in a new browser tab)

    Also checked: Indiana Department of Health: Adjusting Chemical Levels in a Swimming Pool / Water Chemistry Adjustment Guide Official says: Sodium Hypochlorite (12%) 10.7 fl.oz. 1.7 qts 3.3 qts Source page (opens in a new browser tab)

    Checked against the source on 11/9/2026.

  • Liquid chlorine 8.25%: US fl oz to raise free chlorine 1 ppm in 10,000 US gal: 12.93 US fl oz per ppm per 10,000 US gal Other source (worked out)

    Worked out: 128 ÷ (8.25 × 1.2) = 12.93

    EPA-accepted label: B's Pool Supply Sodium Hypochlorite Solution 12.5% (EPA Reg. 55487-20001) Other source says: Total available chlorine is 11.9% Source page (opens in a new browser tab)

    Also checked: Indiana Department of Health: Adjusting Chemical Levels in a Swimming Pool / Water Chemistry Adjustment Guide Official says: Sodium Hypochlorite (12%) 10.7 fl.oz. 1.7 qts 3.3 qts Source page (opens in a new browser tab)

    Also checked: EPA-accepted label: PDQ ChlorSan 8% Sodium Hypochlorite (EPA Reg. 58880-2) Other source says: 80 to 160 oz. of product for each 10,000 gallons of water Source page (opens in a new browser tab)

    Checked against the source on 11/9/2026.

  • Liquid chlorine 10%: US fl oz to raise free chlorine 1 ppm in 10,000 US gal: 10.67 US fl oz per ppm per 10,000 US gal Other source (worked out)

    Worked out: 128 ÷ (10 × 1.2) = 10.67

    EPA-accepted label: B's Pool Supply Sodium Hypochlorite Solution 12.5% (EPA Reg. 55487-20001) Other source says: Total available chlorine is 11.9% Source page (opens in a new browser tab)

    Also checked: Indiana Department of Health: Adjusting Chemical Levels in a Swimming Pool / Water Chemistry Adjustment Guide Official says: Sodium Hypochlorite (12%) 10.7 fl.oz. 1.7 qts 3.3 qts Source page (opens in a new browser tab)

    Also checked: Salt Lake County Health Department (Utah): pool chemical dosages Official says: Sodium Hypochlorite - Bleach 13 fl. oz. ½ gallon 1 gallon Source page (opens in a new browser tab)

    Also checked: Yakima County (Washington): Chemical Dosing chart Official says: Sodium Hypochlorite (Bleach) 13 fluid ounces Source page (opens in a new browser tab)

    Also checked: Multnomah County (Oregon) Environmental Health: Water Treatment - Swimming Pools, EHS-0058 Official says: LIQUID 10% 1pt. 1ppm Source page (opens in a new browser tab)

    Also checked: FPC (fpcusa.com): 10.0% Sodium Hypochlorite product sheet Other source says: Specific Gravity 1.13-1.20 @ 68F/20C Source page (opens in a new browser tab)

    Checked against the source on 11/9/2026.

  • Liquid chlorine 12.5%: US fl oz to raise free chlorine 1 ppm in 10,000 US gal: 8.53 US fl oz per ppm per 10,000 US gal Other source (worked out)

    Worked out: 128 ÷ (12.5 × 1.2) = 8.53

    EPA-accepted label: B's Pool Supply Sodium Hypochlorite Solution 12.5% (EPA Reg. 55487-20001) Other source says: Total available chlorine is 11.9% Source page (opens in a new browser tab)

    Also checked: Indiana Department of Health: Adjusting Chemical Levels in a Swimming Pool / Water Chemistry Adjustment Guide Official says: Sodium Hypochlorite (12%) 10.7 fl.oz. 1.7 qts 3.3 qts Source page (opens in a new browser tab)

    Also checked: HASA liquid chlorine page Other source says: 12.5 PPM of free chlorine in 10,000 gallons—delivered by a single gallon of HASA’s 12.5% liquid chlorine Source page (opens in a new browser tab)

    Also checked: EPA-accepted label: B's Pool Supply Sodium Hypochlorite Solution 12.5% (EPA Reg. 55487-20001) Other source says: For a new pool or when opening the pool in the spring, super chlorinate with 52 to 104 fl. oz. of product Source page (opens in a new browser tab)

    Checked against the source on 11/9/2026.

  • Dry chlorine: oz to raise free chlorine 1 ppm in 10,000 US gal = 1.3 / (strength % / 100): 1.3 oz of 100% available chlorine per ppm per 10,000 US gal Official

    Indiana Department of Health: Adjusting Chemical Levels in a Swimming Pool / Water Chemistry Adjustment Guide Official says: 1.0 ppm equals about .083 lbs of chemical per 10,000 gallons of water* or 1.3 oz per 10,000 gallons**. Source page (opens in a new browser tab)

    Also checked: Indiana Department of Health: Adjusting Chemical Levels in a Swimming Pool / Water Chemistry Adjustment Guide Official says: Calcium Hypochlorite (67%)* 2 oz 10 oz 1.3 lb Source page (opens in a new browser tab)

    Also checked: Indiana Department of Health: Adjusting Chemical Levels in a Swimming Pool / Water Chemistry Adjustment Guide Official says: Dichlor (56%) 2.4 oz 12 oz 1.4 lbs Source page (opens in a new browser tab)

    Also checked: Indiana Department of Health: Adjusting Chemical Levels in a Swimming Pool / Water Chemistry Adjustment Guide Official says: Dichlor (62%) 2.1 oz 10.75 oz 1.3 lbs Source page (opens in a new browser tab)

    Also checked: Indiana Department of Health: Adjusting Chemical Levels in a Swimming Pool / Water Chemistry Adjustment Guide Official says: Trichlor 1.5 oz 7.5 oz 14 oz Source page (opens in a new browser tab)

    Checked against the source on 11/9/2026. Re-opened by a second checker on 11/9/2026, who matched the source's words to this figure. Looked up again on 11/10/2026 by a checker who couldn't see our figure: it came back with the same figure.

  • Cal-hypo 65%: oz to raise free chlorine 1 ppm in 10,000 US gal: 2 oz per ppm per 10,000 US gal Official (worked out)

    Worked out: 1.3 ÷ 0.65 = 2.0 (matches all four charts)

    Multnomah County (Oregon) Environmental Health: Water Treatment - Swimming Pools, EHS-0058 Official says: GRANULAR 65% 2 oz. 1ppm Source page (opens in a new browser tab)

    Also checked: Yakima County (Washington): Chemical Dosing chart Official says: Calcium Hypochlorite 2.0 ounces Source page (opens in a new browser tab)

    Also checked: Salt Lake County Health Department (Utah): pool chemical dosages Official says: Calcium Hypochlorite 2 oz. 10 oz. 20 oz. Source page (opens in a new browser tab)

    Also checked: Indiana Department of Health: Adjusting Chemical Levels in a Swimming Pool / Water Chemistry Adjustment Guide Official says: Calcium Hypochlorite (67%)* 2 oz 10 oz 1.3 lb Source page (opens in a new browser tab)

    Checked against the source on 11/9/2026.

  • Dichlor 56%: oz to raise free chlorine 1 ppm in 10,000 US gal: 2.32 oz per ppm per 10,000 US gal Official (worked out)

    Worked out: 1.3 ÷ 0.56 = 2.32

    Indiana Department of Health: Adjusting Chemical Levels in a Swimming Pool / Water Chemistry Adjustment Guide Official says: Dichlor (56%) 2.4 oz 12 oz 1.4 lbs Source page (opens in a new browser tab)

    Also checked: Yakima County (Washington): Chemical Dosing chart Official says: Dichlor 2.5 ounces Source page (opens in a new browser tab)

    Also checked: Salt Lake County Health Department (Utah): pool chemical dosages Official says: Dichlor 2 ½ oz. 12 ½ oz. 25 oz. Source page (opens in a new browser tab)

    Checked against the source on 11/9/2026. Re-opened by a second checker on 11/9/2026, who matched the source's own words quoted here.

  • 3-inch trichlor tablets: US gallons treated per tablet per week (label rate): 10,000 US gallons per tablet per week Other source

    HTH 3" Chlorine Tabs Advanced product page Other source says: Add one tablet per 10,000 gallons of pool water every week, or as often as needed, to maintain a free available chlorine level of 1–4 ppm. Source page (opens in a new browser tab)

    Also checked: EPA-accepted label: Tarry trichlor 8 oz tablets/sticks (Qualco, EPA Reg. 3525-120) Other source says: Suggested dosage is one {tablet}{stick} per 11,500 gallons of pool water per week. Source page (opens in a new browser tab)

    Checked against the source on 11/9/2026. Re-opened by a second checker on 11/9/2026, who matched the source's words to this figure.

  • Stabilizer (CYA) added by trichlor for each 1 ppm of chlorine: 0.6 ppm CYA per ppm FC Other source

    the PHTA pool industry committee Other source says: When trichlor is used, 0.6 ppm of cyanuric acid is added to the water for each ppm of available chlorine added. Source page (opens in a new browser tab)

    Also checked: Trouble Free Pool forum 'Compiled info on chemicals' (first-year owner) Other source says: It will add .6 part CYA for every 1 part of chlorine it adds. Source page (opens in a new browser tab)

    Checked against the source on 11/9/2026. Re-opened by a second checker on 11/9/2026, who matched the source's words to this figure.

  • Stabilizer (CYA) added by dichlor for each 1 ppm of chlorine: 1 ppm CYA per ppm FC Official (worked out)

    Worked out: Yakima: 1.6 lb = 25.6 oz raises stabilizer 10 ppm; at 2.5 oz per ppm, 25.6 oz raises chlorine 10.24 ppm; 10 ÷ 10.24 = 0.98. Salt Lake: 26 oz raises stabilizer 10 ppm; at 25 oz per 10 ppm, 26 oz raises chlorine 10.4 ppm; 10 ÷ 10.4 = 0.96. Rounded up to 1.0.

    Yakima County (Washington): Chemical Dosing chart Official says: Dichlor 1.6 pounds Source page (opens in a new browser tab)

    Also checked: Yakima County (Washington): Chemical Dosing chart Official says: Dichlor 2.5 ounces Source page (opens in a new browser tab)

    Also checked: Salt Lake County Health Department (Utah): pool chemical dosages Official says: Dichlor 13 oz. 26 oz. Not recommended Source page (opens in a new browser tab)

    Also checked: Trouble Free Pool forum 'Compiled info on chemicals' (first-year owner) Other source says: It will add .9 parts CYA for every 1 part chlorine it adds. Source page (opens in a new browser tab)

    Checked against the source on 11/9/2026.

  • Circulation time stated on balancer products: 4 hours Other source

    Leslie's: Soda Ash pH Up Other source says: You can swim after 4 hours of circulation once the product is fully dissolved. Source page (opens in a new browser tab)

    Also checked: Leslie's: Alkalinity Up Other source says: Takes around 4 hours for full circulation of Alkalinity Up. Source page (opens in a new browser tab)

    Also checked: Leslie's: Dry Acid pH Down Other source says: You can swim after 4 hours of circulation Source page (opens in a new browser tab)

    Checked against the source on 11/9/2026. Re-opened by a second checker on 11/9/2026, who matched the source's words to this figure.

  • Chlorine (liquid, cal-hypo, dichlor, tablets, shock): when labels allow swimming: at or below your label's level Other source

    EPA-accepted label: B's Pool Supply Sodium Hypochlorite Solution 12.5% (EPA Reg. 55487-20001) Other source says: Do not enter treated pool above 4 ppm chlorine level due to risk of bodily harm. Source page (opens in a new browser tab)

    Also checked: EPA-accepted label: PDQ ChlorSan 8% Sodium Hypochlorite (EPA Reg. 58880-2) Other source says: Reentry into treated pools is prohibited above levels of 4.0 ppm due to risk of bodily harm. Source page (opens in a new browser tab)

    Also checked: HTH Pool Care Shock product page Other source says: Do not enter the pool until free available chlorine levels return to 1–4 ppm. Source page (opens in a new browser tab)

    Also checked: EPA-accepted label: Tarry trichlor 8 oz tablets/sticks (Qualco, EPA Reg. 3525-120) Other source says: Do not enter pool until the chlorine residual drops to 2.0 ppm (parts per million). Source page (opens in a new browser tab)

    Also checked: CDC Model Aquatic Health Code, 5th edition (2024), Code Official says: Maximum DPD-FC concentrations shall not exceed limits specified on the product label. Source page (opens in a new browser tab)

    Checked against the source on 11/9/2026. Re-opened by a second checker on 11/9/2026, who matched the source's words to this figure. Looked up again on 11/10/2026 by a checker who couldn't see our figure: it came back with the same figure.

  • US gallon to liters: 3.785412 L per US gal Official

    NIST Special Publication 811, Appendix B.8 conversion factors Official says: gallon (U.S.) (gal) | liter (L) | 3.785 412 | E+00 Source page (opens in a new browser tab)

    Checked against the source on 11/9/2026. Re-opened by a second checker on 11/9/2026, who matched the source's words to this figure.

  • US fluid ounce to milliliters: 29.57353 mL per US fl oz Official

    NIST Special Publication 811, Appendix B.8 conversion factors Official says: ounce (U.S. fluid) (fl oz) | milliliter (mL) | 2.957 353 | E+01 Source page (opens in a new browser tab)

    Checked against the source on 11/9/2026. Re-opened by a second checker on 11/9/2026, who matched the source's words to this figure.

  • Ounce (avoirdupois) to grams: 28.34952 g per oz Official

    NIST Special Publication 811, Appendix B.8 conversion factors Official says: ounce (avoirdupois) (oz) | gram (g) | 2.834 952 | E+01 Source page (opens in a new browser tab)

    Checked against the source on 11/9/2026. Re-opened by a second checker on 11/9/2026, who matched the source's words to this figure.

  • Pound to kilograms: 0.4535924 kg per lb Official

    NIST Special Publication 811, Appendix B.8 conversion factors Official says: pound (avoirdupois) (lb) | kilogram (kg) | 4.535 924 | E-01 Source page (opens in a new browser tab)

    Checked against the source on 11/9/2026. Re-opened by a second checker on 11/9/2026, who matched the source's words to this figure.