Measuring water quality

Measuring water disinfectants

The level of disinfectant should be measured before and after use, or at least daily if not in use. We recommend you purchase a good quality test kit that can measure different types of disinfectants. Follow the instructions that come with your test kit. Make sure whoever does the testing knows how to respond to a specific reading or test result.

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.

Types of Chlorine

  • Free Available Chlorine (FAC): Chlorine that has not yet reacted with any organic material.
  • Combined Available Chlorine (CAC): Chlorine that has already reacted with organic material present in a hot tub or pool; therefore, it is much less effective.
  • Total Available Chlorine (TAC): Is the sum of free available chlorine plus the combined available chlorine as per the formula TAC=FAC+CAC.

Other disinfectants

Ultraviolet (UV) or ozone treatment systems help control bacteria, but they are not a substitute for disinfection. 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. If you are using another form of disinfection such as ozone, it must be used in combination with chlorine or bromine to create a disinfection residual.

Measuring pH and water quality

It is very important to maintain the pH of the water in the 7.2 to 7.8 range. Hot tub or pool water out of this range reduces 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.

Chlorine is measured in parts per million (ppm). Stabiliser chlorine should be avoided unless you have an outdoor pool, and should not exceed 30-50ppm. The table below lists recommended ranges for both pools (less than 30ºC) and hot tubs (more than 30ºC) water quality measures.

Parameter Minimum Recommended Maximum
Free Chlorine (less than30ºC/86ºF) 0.5ppm 2.0-5.0ppm 5.0ppm
Free Chlorine (morethan30ºC/86ºF) 1.5ppm 3.0-5.0ppm 5.0ppm
Bromine(less than30ºC/86ºF) 1.5ppm 3.0-5.0ppm 5.0ppm
Bromine(morethan30ºC/86ºF) 2.5ppm 5.0-8.0ppm 8.0ppm
pH 7.2 (Target 7.4) 7.8
Total Alkalinity CaCo3 80ppm
Cyanuricacid (outdoor pools only) 30ppm 30-50ppm 80ppm

Getting rid of excess chlorine

'Shock treatment' is a process for getting rid of the combined residual chlorine in a hot tub or pool. Regular shock treatment or dosing is recommended when combined, residual chlorine begins to accumulate in the water and can lead to unwanted odors and eye irritation. Ideally, shock treatment is done before the combined residual chlorine is more than 0.5ppm. In hot tubs, you can also just replace all of the water instead of doing a shock treatment.

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.