Hot tub / spa chemicals & water test strips (C) Daniel FriedmanHot Tub, Spa, Whirlpool Bath Chemicals
Guide to hot tub water treatment, disinfection, chlorine or bromine

  • SPA / HOT TUB CHEMICALS & CHLORINATION - CONTENTS: how to use chlorine or bromine and other chemicals & treatments to maintain a hot tub or spa; how to test chlorine, bromine, pH, alkalinity, hardness and other spa or hot tub water properties to maintain a safe, sanitary hot tub.
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Hot tub & spa or whirlpool bath chemical & water treatment guide:

Here we provide a simple table showing how to use chlorine or bromine and other chemicals & treatments to maintain a hot tub or spa, We explain how to use simple test strips to test the level of chlorine, bromine, pH, alkalinity, hardness and other spa or hot tub water properties in order to maintain a safe, sanitary hot tub or spa.

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Hot Tub / Spa Water Chemistry Recommendations

At the top of this page we illustrate the typical chemicals and pool or spa water test strips needed to maintain a hot tub or spa. After the table of recommended hot tub or spa water chemical levels given just below, we include examples of using test strips to measure these hot tub or spa water chemistry levels / numbers.

Hot Tub or Spa Water Chemistry Guidelines

Recommended Pool Chemical 

Hot Tub / Spa Water 

Recommended Level
Action to Correct Pool Water Chemistry
To Raise the Level To Lower the Level

pH & Alkalinity for Hot Tubs & Spas


pH measures the acidity or alkalinity of a solution where 7 is neutral, lower numbers are acidic and higher numbers are basic.

7.2 - 7.83b

Add Soda Ash

Add pH increaser product

Add "dry acid" product

Add pH decreaser product

Add Muriatic Acid or Sodium Bisulphate

Watch out: acids can cause dangerous burns or other personal injury and can be fatal if ingested. Be sure to follow the manufacturer's instructions.

Total Alkalinity (TA level)

Alkalinity measures the ability of water to neutralize an acid.

50 ppm 3b

80-120 ppm (most-common)

100 - 130 ppm3a

Add Bio-Guard or similar product

Add Soda Ash

Add Sodium Bicarbonate

Add "dry acid" product

Add Muriatic Acid

Water Hardness or Calcium Hardness (CH level) 3b

Water hardness measures the amount of mineral salts, chiefly calcium (Ca) and magnesium (Mn) dissolved in water. Harder water has higher levels of these salts.

150 -250 ppm

Add a calcium / water hardness increaser

Watch out: water that is too soft can damage hot tub or spa equipment by corrosion of metal parts.

Add a water softener or calcium decreaser or stain & scale product or similar water conditioner

Watch out: hard water (too high in calcium or magnesium) clogs equipment, particularly hot water piping & heating equipment and can damage pumps, valves, controls in a hot tub or spa.


Chlorine Treatments for Hot Tubs & Spas

Chlorine (Un stabilized) 1 0.3 - 1.0 ppm chlorine Add Chlorine chemical Wait - chlorine will naturally dissipate
Chlorine (Stabilized)3a 1.0 - 3.0 ppm chlorine Add Chlorine chemical Wait - chlorine will naturally dissipate
Chlorine (Free chlorine)3b 1 - 3 ppm chlorine Add Chlorine chemical Wait - chlorine will naturally dissipate
Chlorine stabilizer
(Cyanuric acid)
40 - 70 ppm chlorine Add Stabilizer Dilution - partially drain and refill the hot tub or spa with water that has not been treated with Cyanuric Acid.
Chlor Brite type shock treatment 10 ppm free chlorine FC Add Chlorine chemical Wait - chlorine will naturally dissipate
Algae control 2 Keep chlorine level at 0.5 ppm or above at all times. See notes Wait - chlorine will naturally dissipate

Bromine5 Treatments for Hot Tubs & Spas

Initial Bromide shock treatment / reserve:

10 ppm bromine

Watch out: do not enter the hot tub until the bromine level is below 10 ppm

Weekly hot tub non-chlorine shock treatment is required

Add sodium bromide + a shock oxidizer. Because bromine tablets may take a long time to dissolve, either crush the tablets or use a powdered sodium bromide product.  
Bromine level for hot tub use

2-6 ppm bromine

Add bromine tablets or use a bromine dispenser and oxidizer  
Weekly Bromine System Hot Tub / pa Maintenance: Add 2-3 non-chlorine shock tablets formulated for use in bromine systems with pump and jets running for at least 15 minutes; test bromine, pH, and alkalinity levels. Adjust alkalinity and bromine as needed. Some sources3b suggest using un-scented laundry bleach at 1 cup of laundry bleach (5.25% concentration sodium hypochlorite) per 250-300 gallons of water, or 3/4 cup of "super bleach" (6% concentration) for the same water volume.


Watch out: keep all spa chemicals & treatments out of reach of children. Some of these can cause fatal poisoning or serious burns.

Watch out: hot tub or spa chemical treatment and water chemistry level requirements are different from those of a typical swimming pool. That is principally because the hot tub water is frequently heated to a much higher temperature. Do not assume that chemical treatments formulated for use in swimming pools are also suitable for use in hot tubs or spas.

1. Disinfectant: Chlorine or Bromine level for hot tub: Both chlorine and bromine are disinfectants commonly used in hot tubs and spas. Chlorine treatment generally costs less but requires more frequent dosing. The combination of heating and aeration of hot tub or spa water means that both of these chemicals will dissipate rapidly, but chlorine dissipates more rapidly than bromine. For the specific hot tub / spa described in the article above, local experts recommended the following:

  • Chlorine maintenance level: between 1.5 - 2.0 ppm
  • Check the chlorine level daily
  • Shock level for initial treatment when you are first filling or re-filling a hot tub or spa is needed, and shock treatment may also be needed in your hot tub if problems are observed. In general shock treatment of a hot tub means that you temporarily increase the chlorine level to 3 x the above recommended levels. Or you may elect to use a special hot tub di-chlor chlorine shock treatment product. Leslie's Chlor Brite, a shock treatment product, recommends that you add that product until the chlorine level is at about 10 ppm of free chlorine (FC).

2. For controlling algae, look for green "blooms" of algae in the pool or hot tub water. Algae may be killed-off by shocking or "super-chlorinating" the pool by adding un-stabilize chlorine. Follow the manufacturers' recommendations. Algae control chemicals are available from your pool or hot tub / spa supplier. Algae that has been killed by chlorination may be removed by the hot tub or spa filter but it's likely that you'll then need to remove and clean the filter cartridge.

3.a. The table above is excerpted and adapted from the Hayward Pool Products Star-Clear filter manual PDF whose link is included in the references at the end of this article or found online at This is general advice. Your local hot tub or spa consultant or manufacturer may have different recommendations specific to the water chemistry and properties where you live.

3.b. Additional table data is adapted from other hot tub treatment products such as Chlor BriteTM and troublefreepool cited below.

4. Minimum daily hot tub / spa operation & chemical testing: typical spa / hot tub instructions require that the spa pump and filter system be operated at least 2 hours / day even if you are not using the system. For details see
"Spa Preparation & Maintenance, A Complete Spa Care Guide, Spa Water Testing, Spa Chemical Program, Spa Cleanup" [PDF],
Leisure Time Chemical Corporation, Irwindale CA 91707. (1984) This company also provides a Hot Tub / Spa operating manual with recommendations for water and chemical maintenance. Website:, this spa guide was provided at the original installation of the hot tub discussed in this article series.

5. Bromine: Sodium bromide used as a hot tub or spa sanitizer. Bromine tablets used in spas and hot tubs often contain both bromine and chlorine The chlorine serves as an oxidizer needed to active the bromine sanitizer.

  • In a two-step hot tub bromine treatment process, bromine tablets are added to reach the required concentration of bromine in ppm and then an oxidizer is added weekly
  • In a three-step hot tub or spa bromine treatment process (an alternative to the two-step method), additional bromine tablets are added in a floating dispenser to keep the bromine level constant.

Hot Tub / Spa Chemical Test Strip Examples

Leisure Time Pool, Spa or Hot Tub water chemistry test strips (C) Daniel Friedman

Above: Leisure Time Spa / Pool water test strips indicate water pH, Alkalinity and Free Chlorine as we illustrate successively below.

Watch out: if your pool or hot tub / spa water test strips are quite old, they may no longer be accurate. Buy a new set.

pH test for Hot Tub or spa or pool water (C) Daniel Friedman

Above: pH test showing a pH between 6.8 and 7.2.

Below: spa, hot tub or pool water alkalinity test.

Hot tub or spa water alkalinity test (C) Daniel Friedman

Above, the alkalinity test indicates an alkalinity between 80 and 120 ppm.

Below: using a test strip to test for free chlorine. The bottom-most or nearly-white indicator shows that the free chlorine in the water tested was very low. The target chlorine level is 1.5 - 2.0 ppm for the hot tub illustrated in this article series.

Spa / Hot Tub or Pool Test for Chlorine Level (C) Daniel Friedman

Above: the nearly-pure-white result of the bottom-most indicator tab on this test strip indicates almost no free chlorine in the water. This hot tub needs more chlorine added to its water.

Should You Use Ozone as an Oxidizer in Hot Tubs, Spas & Swimming Pools?

Probably not.

The use of ozone (O3) has been promoted by some spa, hot tub and swimming pool equipment & supply producers or vendors as an oxidant or oxidizing agent useful to improve water quality by removing " non-living bather waste such as body oils, cosmetics, sun tan lotions, perspiration, urine."

Watch out: Wojtowicz (2001) reports that in general ozone is ineffective for this application and that in any event it should not be used by methods that might expose the hot tub, spa, or pool users to elevated levels of ozone. That author also found that other claims of the benefits of ozone use in hot tubs and spas were not substantiated.

Ozonating the water while the spa is in use is not recommended because the unabsorbed ozone in the ozonator vent gas can amount to 60 ppm. - (Wojtowicz 2001 p. 147)

A number of UV ozonators have been evaluated and found to be unsuitable for pool or spa use. Although UV ozonator manufacturers typically claim lower chlorine consumption (typically 60 to 90%) and the ability to operate pools and spas at lower chlorine concentrations, no independent data are provided to support these claims.  (Wojtowicz 2001)

Details about using ozone to improve water quality in spas, hot tubs, spas, or swimming pools are

Separately at OZONE HAZARDS readers will find a series of articles about both successful and un-successful, even dangerous applications of ozone. Also see OZONE GAS EXPOSURE EFFECTS.


Continue reading at HOT TUB SPA WHIRLPOOL OPERATION & REPAIR - home, or select a topic from closely-related articles below, or see our complete INDEX to RELATED ARTICLES below.

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