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How to shock a pool, and how often

Doses checked 11/10/2026

Shocking (superchlorinating) means adding enough chlorine to break down combined chlorine. Shock when combined chlorine is above 0.4 ppm, with nobody in the pool. The calculator raises free chlorine by 10 times your combined chlorine, kept within the 5–10 ppm that labels give, and never past 10 ppm in total.

Your pool and readings
Pool size

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

Leave it empty and we assume the strongest we accept, so the amount comes out low.

Needed: without it we give no shock amount.

Total chlorine minus free chlorine.

Checked on every build: 32 tests of the sums this calculator runs, including 6 amounts printed in published charts, labels and manuals (ours must match them, or land under them where we start low on purpose) and 10 tests of its limits: caps, smaller rounds, and the cases where it gives no amount.

How much shock

Multnomah County (Oregon) Environmental Health works it out from combined chlorine: In this situation, you need 0.8 ppm x 10, or 8 ppm of chlorine to superchlorinate. Chlorine labels give a shock dose for each 10,000 gallons of water to yield 5 to 10 ppm available chlorine by weight. The calculator uses 10 times your combined chlorine, held inside that range, then limits it so free chlorine should end at or below 10 ppm, because above that CDC says a test may read falsely low.

It gives no shock amount if free chlorine is already high enough that even the smallest label dose would pass 10 ppm, or if you leave free chlorine empty: then it has to assume the cautious case.

For example, say your pool holds 20,000 US gallons, free chlorine is 2 ppm, combined chlorine is 0.6 ppm and stabilizer is 30 ppm, and you have liquid chlorine at 12.5%. The calculator raises free chlorine by 6 ppm, to about 8 ppm, with 3.1 US qt (102 US fl oz) (3,015 mL) of liquid chlorine.

How often to shock a pool

When the test says so, not on a set day. Test combined chlorine: CDC's model code for public pools says to reduce the concentration of COMBINED CHLORINE (chloramines) in the water when the concentration exceeds 0.4 ppm (mg/L). Multnomah County (Oregon) Environmental Health says Breakpoint chlorinate when combined chlorine exceeds 0.5 ppm, or when chloramines are first detected. The calculator uses the lower figure, 0.4 ppm.

Labels also name times to shock. One liquid chlorine label says For a new pool or when opening the pool in the spring, super chlorinate with 52 to 104 fl. oz. of product.

How to shock a pool

  1. Test free chlorine, combined chlorine and stabilizer. Combined chlorine is total chlorine minus free chlorine.
  2. Make sure nobody is in the pool: Multnomah County (Oregon) Environmental Health says shocking should only be done when the pool is closed.
  3. Put on the protective gear your label asks for, such as goggles and gloves, and run the pump.
  4. Add the shock as your label directs. Never add shock (cal-hypo or any other chlorine product) through the skimmer, or through any floater or feeder that holds or has held tablets, and never put different chlorine products in the same feeder.
  5. Keep everyone out until free chlorine is back at or below your label's level, then retest combined chlorine. If it is still above 0.4 ppm after a shock and a retest, ask a pool professional.

Which product to shock with

The calculator covers liquid chlorine, cal-hypo and dichlor. Dichlor adds stabilizer, about 1 ppm for each ppm of chlorine, so shocking with it often can push stabilizer up. The calculator gives no shock amount for tablets.

Shocking a green or very cloudy pool

The calculator gives no shock amount for green, black or very cloudy water. That water needs a professional test and plan: keep everyone out and ask a pool professional. See green pool water and cloudy pool water.

Questions people ask

What is pool shock?

A large dose of chlorine, sold as liquid chlorine or as granules such as cal-hypo or dichlor, added to break down combined chlorine. Shocking is also called superchlorinating.

How much shock do I add to my pool?

The calculator raises free chlorine by 10 times your combined chlorine, within the 5–10 ppm that labels give, and keeps the total at or below 10 ppm. The amount then depends on your pool size and product.

How much liquid chlorine do I need to shock a pool?

Enter your pool size, free chlorine, combined chlorine and the liquid's strength in the calculator. By our figures, 8.53 US fl oz of liquid chlorine 12.5% raises free chlorine by one ppm in 10,000 US gallons.

How often should I shock my pool?

When combined chlorine tests above 0.4 ppm, the level at which CDC's model code for public pools calls for action. Test it rather than shocking on a schedule.

When can I swim after shocking?

Once free chlorine is back at or below your label's level. One shock product's page says Do not enter the pool until free available chlorine levels return to 1–4 ppm.

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The charts behind this page

Show all 19 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.

  • 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.

  • 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.

  • Breakpoint (shock) chlorine raise = combined chlorine x this number: 10 times combined chlorine Official

    Multnomah County (Oregon) Environmental Health: Water Treatment - Swimming Pools, EHS-0058 Official says: In this situation, you need 0.8 ppm x 10, or 8 ppm of chlorine to superchlorinate. 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.

  • Chlorine raise that pool chlorine labels give for superchlorinating (shock): 5–10 ppm Other source

    EPA-accepted label: B's Pool Supply Sodium Hypochlorite Solution 12.5% (EPA Reg. 55487-20001) Other source says: for each 10,000 gallons of water to yield 5 to 10 ppm available chlorine by weight. 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: BioGuard Master Calcium Hypochlorite 67% (Bio-Lab, EPA Reg. 5185-238) Other source says: Apply this product at a rate of 1 pound (see Application Methods) per 10,000 gallons of 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.

  • 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 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.

  • 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.

  • 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.

  • You should be able to see the drain at the bottom of the deep end: the drain at the bottom of the deep end can be seen Official

    CDC healthy swimming infographic: inspection Official says: Drain at the bottom of the deep end is visible. Source page (opens in a new browser tab)

    Also checked: Licking County Health Department (Ohio): Pool and Spa Water Chemistry Adjustment Guide Official says: Clarity Deepest point of pool visible from deck 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.