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Hot tubs and whirlpool baths can provide a fertile breeding ground for a number of bacteria that cause infection or disease. This includes the Legionella bacteria that cause Legionnaires' Disease, which can be fatal. As well, the Pseudomonas bacteria can cause a number of serious infections, such as severe skin rashes, eye and ear infections, and pneumonia. These bacteria can be easily controlled and removed by maintaining the disinfectant level of the water.
You can prevent illness from hot tub use by learning about and maintaining safe water quality in your hot tub. It is the owner's responsibility to ensure the hot tub is clean and the water is properly disinfected to prevent the spread of germs and disease.
It is important to maintain the proper level of disinfectant to ensure clean and safe water in hot tubs and pools. Chlorine is the most commonly used disinfectant. Some owners may use bromine instead of chlorine in hot tubs, but this must be used at higher levels to be effective. Both chlorine and bromine kill viruses and bacteria. However, they also react with other organic material in the water including dirt, soap, shampoo, body oils, perspiration, food and drinks. The more a hot tub is used, the faster the disinfectant in the water gets used. Always check the level of chlorine or other disinfectant in the water, and add more if required.
Measure Water Disinfectants
The level of disinfectant in your hot tub should be measured before and after use, or at least daily if not in use.
Many test kits available from pool equipment dealers can measure two different forms of chlorine found in the water. It is recommended to measure both types of chlorine. One form of chlorine is free residual chlorine, which has not yet reacted with any organic material. The other form is combined residual chlorine, which has already reacted with organic material present in the hot tub; therefore, it is much less effective. This is calculated by subtracting the amount of free residual chlorine from the total residual chlorine measured by the test kit.
It is important to maintain the proper level of disinfectant. Free residual chlorine should be maintained at 3 ppm (parts per million) in hot tubs and not fall below 1 ppm. Bromine should be maintained at 4.5 ppm in hot tubs and not fall below 2 ppm.
Other Disinfectants
Ultraviolet (U.V.) or ozone treatment systems help control bacteria, but they are not a substitute for disinfection with chlorine or bromine because they do not leave left over disinfectant in the water. Ozone helps disinfection since it will destroy some of the material that uses up disinfectants. Special care should be taken with ozone because it can cause eye and lung damage. Make sure no ozone bubbles are entering the bathing area and there is no ozone smell.
Measure pH and Water Quality
It is very important to maintain the pH of the water in the 7.2 to 7.8 range. Pool water out of this range can lessen the disinfecting power of chlorine. It can also cause eye and mucous membrane irritation. Measure pH daily and maintain it in this range. Your pool supplier will carry test kits for pH, as well as chemicals to adjust the pH.
Other factors can affect the performance of disinfectants or lead to maintenance problems. To avoid these problems, you should monitor the water quality. The following is a summary of recommended ranges of water quality measures.
| Disinfectant Bromine Free Chlorine Combined Chlorine |
4.5 ppm (never less than 2.0 ppm) 3.0 ppm (never less than 1.0 ppm) 0.1 - 0.5 ppm |
| PH | 7.2 - 7.6 (Target 7.5) |
| Alkalinity CaCO3 |
80 - 100 ppm (50 - 180 ppm are extreme limits) |
| Calcium |
200 - 400 ppm (150 - 1000 ppm Hardness are extreme limits) |
| Stabilizer Cyanuric Acid |
30 - 50 ppm |
| Organic Load |
There should be no visible particles; strainers and filters should be regularly cleaned |
Your dealer can help you with more advanced chemical analyses.
Remember to use and store your pool chemicals safely as they can be dangerous. Follow safety instructions on the product label and safety data sheets.
Regular shock treatment is recommended
When combined residual chlorine begins to accumulate in the water, it can lead to unwanted odors and eye irritation. Shock treatment is a process for getting rid of the combined residual chlorine in a hot tub or pool. Ideally, shock treatment is done before the combined residual chlorine exceeds 0.5 ppm.
Most pool suppliers can provide instructions or chemicals for shock treating a hot tub or pool. This helps clear the water and remove contaminants. Make sure the chlorine level is back to normal before you enter the tub.
Keep the pump going 24 hours a day
Between periods of use, water in the tub's plumbing lines can become stagnant and grow bacteria or fungus. You can prevent this by:
Some spas have secondary circulation pumps that run 24 hours a day. These systems may bypass some water lines and still leave water sitting stagnant in those lines. Ask your dealer for help.
Clean your hot tub regularly
Your hot tub should be cleaned and restarted every two months. You should also drain and clean your hot tub if any of the following problems occur:
For more information on maintaining safe water quality in hot tubs, contact your local public health inspector. See also BC HealthFile #27a Hot Tubs: Health and Safety Tips.
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