Spas, Hot Tubs, Pools — How Infections and Disease Risks Occur

by Jay | Updated on July 26th, 2022

When a car or a room is rented, the occupant expects that everything will be well – clean, orderly, and proper. Likewise, if one uses a hot tub, spa, or pool, one should expect the same thing – clean, orderly, and proper. But, surprisingly, or unfortunately, this is not always true.

In 2004 the CDC published a disturbing summary of spa, hot tub, and whirlpool violations from 5 states. About 11% (500/4,533) of these spa inspections resulted in the immediate closing of spas until the violation was corrected. Even today, hot tubs, spas, and pools are often unsafe and unacceptable for human occupancy. See why this is so.

swimming pool near palm trees during daytime

Infected Hot Tubs, Spas, and Pools – Microbe Soups

The club member came to the hot tub to relax after a long work day. However, before getting in, she noticed that it was cloudy and had a slight odor that was a bit unpleasant.

Fortunately, she decided to avoid using the tub, showered, and returned home. Unfortunately, this tub was heavily contaminated with several potentially dangerous bacteria. The hot tub also had an inadequate level of bromine disinfectant (sanitizer).

How do bacteria get into hot tubs, spas, and pools? The answer is simple – microbes are shed from the skin and mucous membranes of the bathers into all of these waters. Another bather asks, “Are the microbes dangerous or harmful?” The answer is – the microbes may or may not be harmful. If they are dead, they are not harmful to an infectious disease.

If the microbes are alive, they may be harmful should they be of certain dangerous types such as Pseudomonas aeruginosa, Staphylococcus aureus, or even the common species Escherichia coli or the yeast Candida. For example, Pseudomonas aeruginosa is a well-known culprit of folliculitis, as documented in a hot tub epidemic of softball players in Alaska in 1986.

Spa, Hot Tub, and Pool Infections and Diseases

Some bathers acquire skin and intestinal diseases from recreational waters such as pools, spas, or hot tubs.

  • Bacterial skin diseases may be simple rashes, or more dangerous ulcers, boils, and abscesses.
  • Urinary tract (urethritis, cystitis) and genital (vaginosis) infections may result from using hot tubs and spas.
  • Often the responsible agent is a bacterium such as Pseudomonas aeruginosa, Staphylococcus aureus, or Streptococcus pyogenes. 
  • Candida yeasts may cause infections and spread in hot tubs and spas. Intestinal diseases include selected bacterial and viral infections acquired when contaminated water in the mouth is swallowed.

Since bacteria are common contaminants of the water and derived from the skin and mucocutaneous membranes of bathers, there is a need to remove and destroy these bacteria to prevent infectious diseases continuously.

Importance of Spa Filters and Sanitizers

Continuous removal and destruction of microbes in water can be done. Adequate bromine or chlorine at 2 to 8 ppm (parts per million) and a proper pH of 7.2 to 7.8 is usually sufficient to kill or inactivate many of the bacteria and viruses common in hot tubs, spas, and pools.

Further, efficient pumps and filters assure good circulation and contact of the bromine or chlorine with bacteria and viruses. Filters also trap and remove bacteria which are then killed or inactivated as the bromine or chlorine reacts with the trapped microbes.

Signs of a Healthy Hot Tub, Spa, or Pool

Healthy recreational waters look, feel, and smell good. Such recreational waters are produced by efficient filters and adequate chlorine and bromine levels used at an optimal pH range of 7.2 to 7.8.

All bathers need assurance that their bathing waters are tested, treated, maintained, and recorded in a daily log by qualified personnel. Knowing the basic facts of the bacteriology of hot tubs, spas, and pools is a good first step for users and operators alike.

Bacteriology Facts

Every hot tub or spa comes with instructions and directions which should be read and studied by all owners and maintainers of the hot tub. After this is done, maintenance and microbiology is the most important instruction.

All people who use hot tubs and spas harbor microbes on their skin, mucous membranes, and the digestive tract. Here are some important, basic facts to remember about people, microbes, and hot tubs:

  • some skin, mucus, and tears are shed from everyone’s body throughout the day
  • many of these microbes are bacteria
  • some of the bacteria can cause skin and eye infections
  • bacteria include staphylococci, streptococci, enterics, pseudomonads, and others
  • these bacteria shed from the body can survive in water for varying periods
  • multiple people in a hot tub or spa shed their particular types and kinds of bacteria
  • some bathers will harbor more potentially-dangerous kinds of bacteria than others
  • bacteria in the water may attach to a person’s body and grow on the skin or mucous membranes or within the digestive tract if swallowed, and cause disease
  • persons with obvious skin infections, bandages, diarrhea, intestinal upset, or diapered babies should not use the hot tub since they are more likely to be highly infectious

Bacteriology, pH, Bromine-Chlorine Facts

Hot tub and spa manufacturers usually supply water test kits. Every spa owner should have a water test kit with all the appropriate test strips or tablets. This kit lets the owner determine the pH and concentration of bromine or chlorine — the critical factors needed to maintain healthy water for the spa or hot tub.

Most spas and hot tubs use bromine as the recommended disinfectant. Here are facts and rules for maintaining a health spa or hot tub and for the safe control of microbes:

  • Tablets of bromine are typically used
  • The tablets are held in a float or container with water ports that can be regulated by opening and closing. These ports permit more or less water to enter and exit the float
  • bromine and chlorine are both oxidizing agents that kill or inactivate microbes and maintain good health and sanitized water
  • pH must be appropriately maintained between 7.2 to 7.8 to optimize the activity of bromine or chlorine
  • water tests and checks should be done daily or every other day at a minimum
  • tablets must be replenished regularly depending upon bather load and use
  • the filter and pump should be run often enough to clear the water and circulate the bromine

Healthy and Unhealthy Hot Tubs and Spas Basic Ideas

Included here are the signs of a health spa or hot tub and a summary of the recommended pH and bromine or chlorine levels by the CDC (“Healthy Swimming all year Long,” for routine care:

  • pH 7.2 to 7.8
  • bromine or chlorine level is always at 2.0 to 4.0 or 5 ppm (parts per million)
  • water is clear and free of any obvious debris (hairs or particles)
  • no burning of eyes or irritation of skin during or after use
  • pleasant odor to the hot tub

Of course, any of the opposites of the listing above is undesirable. For example, most people would never enter a cloudy hot tub with or without unpleasant odors.

Maintaining a healthy hot tub or spa helps all those who use that hot tub or spa to have a refreshing time and promote the health of the skin and the body.

Bathing should be the pause that refreshes without fear of infection– nothing more or nothing less could be asked by anyone.


Jay is a health and wellness enthusiast with expertise in water quality and nutrition. As a knowledgeable advocate for holistic well-being, Jay successfully manages Type 2 Diabetes through informed lifestyle choices. Committed to sharing reliable and authoritative insights, Jay combines firsthand experience with a passion for enhancing health."