Residential Hot Tubs and Pools: Safe Water Quality

HealthLinkBC File Number: 
Last Updated: 
September 2015

What are the health concerns of hot tubs and pools?

Hot tubs and pools can provide an environment for bacteria to grow. These bacteria can make you sick with an infection or disease. This includes Legionella bacteria that cause Legionnaires’ Disease, which can be fatal, and Pseudomonas bacteria which can cause a number of serious infections, such as severe skin rashes, eye and ear infections, and pneumonia.

These bacteria can be controlled and removed by maintaining the disinfectant level of the water in your hot tub or pool. Hot tubs and pools that are not properly maintained can also cause injuries such as drowning or entrapment.

How can I make sure the water is safe?

Owners are responsible to ensure their hot tub or pool is clean and the water is properly disinfected to prevent the spread of germs and disease. To make sure the water is clean and safe, you need to maintain the proper levels of disinfectant, pH, and other parameters such as chlorine and bromine. For more information about levels, see Table 1 for pools and Table 2 for hot tubs. It is important to ensure that all chemicals are within the recommended range prior to using your pool or hot tub.

Chlorine and bromine are the most commonly used disinfectants. Both chlorine and bromine kill viruses and bacteria, however their effectiveness is dependent on concentration and pH.

You don’t need to use stabilized chlorine products (Chlorine Cyanurate) if you have an indoor pool. If it is used, you should also measure the amount cyanuric acid. Too much cyanuric acid can create “chlorine lock”, which means the chlorine does not disinfect very well.

If you use disinfectants such as ozone or Ultraviolet (U.V.), it should be in combination with chlorine or bromine to make sure a disinfectant residual is present in the pool itself. 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.

Make sure to maintain a pH between 7.2 and 7.8. This ensures that the chlorine disinfects effectively. If the pH is in this ideal range, it will help reduce eye and mucous membrane irritation that can sometimes be caused by chlorine.

How do I measure water chemistry?

The chemistry of your hot tub or pool water should be measured before and after use, or at least daily if not in use. Pool and hot tub owners should use a test kit that can measure, at minimum, the disinfectants and pH. Your hot tub vendor or chemical supplier can help you with more advanced chemical analyses.

Make sure that whomever tests the water understands the ideal range and what to do if the tests are outside of that range.

Table 1
Pools - Temperature less than 30ºC (86ºF)
Parameter Min Recommend Max
Free Chlorine 0.5 PPM 2.0 to 5.0 PPM 5.0 PPM
Chlorine Cyanurate 1.0 PPM 1.5 to 2.0 PPM 5.0 PPM
Bromine 1.5 PPM 3.0 to 5.0 PPM 5.0 PPM
pH 7.2 7.2 to 7.6 7.8
Total Alkalinity CaCO3 80 PPM   120 PPM
Stabilizer (Cyanuric Acid) (outdoor pools only) 30 PPM 30 to 50 PPM 80 PPM

Min= Minimum; Max = Maximum; PPM = Parts Per Million

Table 2
Hot Tubs - Temperature more than 30ºC (86ºF)
Parameter Min Recommend Max
Free Chlorine 1.5 PPM 3.0 to 5.0 PPM 5.0 PPM
Chlorine Cyanurate 2.0 PPM 2.0 to 3.0 PPM 5.0 PPM
Bromine 2.5 PPM 5.0 to 8.0 PPM 8.0 PPM
pH 7.2 7.2 to 7.6 7.8
Total Alkalinity CaCO3 80 PPM   120 PPM

Always use and store your pool chemicals safely as they can be dangerous. Follow safety instructions on the product label and safety data sheets, and always keep out of reach of children.

When pre-mixing chemicals, always pour water in mix first, then adding chemicals second.

Regular shock treatment is recommended

Disinfectants react with organic material in the water including: dirt, soap, shampoo, body oils, perspiration (sweat), food, and drinks. Chlorine that has reacted with organic material is known as “combined available chlorine” (CAC). It is less effective at disinfecting and produces unpleasant odours and eye irritation.

Chlorine that has not reacted with any organic material is known as “free available chlorine” (FAC), and is an effective disinfectant.

Test kits will generally measure “free available chlorine” and “total available chlorine” (TAC). To determine the” combined available chlorine” in the pool, use this formula: TAC – FAC = CAC

The more hot tubs and pools are used, the faster the disinfectant in the water gets turned into combined chlorine. Shock treatment is a process for getting rid of the combined available chlorine in a hot tub or pool, and can be done by raising the chlorine level to 10x the normal concentration, and then letting it sit until the free chlorine levels drop back down to recommended ranges. Ideally, shock treatment is done before the combined available chlorine is more than 0.5ppm.

In hot tubs, due to the relatively small volume of water, it is often easier to replace all of the water instead of doing a shock treatment. Pool suppliers can provide chemicals that will do a non-chlorine shock treatment. The use of non-chlorine shock treatment can be effective, however it may impact accuracy of chlorine test kits.

Keep the pump going 24 hours a day

Plumbing lines in hot tubs and pools can become stagnant (stop moving) and grow bacteria or fungus. You can prevent this by:

  • running a pump 24 hours a day to circulate water through all the pipes; or
  • setting a timer to turn the pump on for a few hours, at least twice a day, to flush out all the lines; and
  • making sure that all filters and pumps are maintained according to the manufacturer’s recommendations.

Some hot tubs 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. Always ask your vendor or pool supplier for advice and recommendations.

Clean your hot tub and pool regularly

Your cleaning schedule will vary depending upon how many people use your pool or hot tub and how often it is used. As a minimum, clean it as per the manufacturer’s instructions. You should also drain and clean your hot tub or pool if any of the following problems occur:

  • complaints of eye, ear or skin irritations after using the pool or hot tub; or,
  • proper disinfectant levels have not been maintained.

For More Information

For more information on maintaining safe water quality in hot tubs and pools, contact your local environmental health office or your local pool and hot tub service provider.

For health and safety tips see HealthLinkBC File #27a Residential Hot Tubs and Pools: Health and Safety Tips.

Is it an emergency?

If you or someone in your care has chest pains, difficulty breathing, or severe bleeding, it could be a life-threatening emergency. Call 9-1-1 or the local emergency number immediately.
If you are concerned about a possible poisoning or exposure to a toxic substance, call Poison Control now at 1-800-567-8911.

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