Lack of disinfection in a spa, for even a short time, can provide a breeding ground for skin rashes, sickness, and even life-threatening diseases.

There are a number of waterborne pathogens that can causes illnesses from moderate to severe that can thrive in the warm environment that a spa provides. Many of these pathogens live in the biofilms that tend to coat the internal plumbing of the spa. The biofilms are highly resistant to normal disinfection and tend form when sanitizing efforts are sporadic.

In a hot tub, biofilms are a rich mixture of bacteria, fungi, algae, yeasts, protozoa, and microorganisms combined with hair, skin cells, and debris that attach to the hidden inner walls of pipes and plumbing components.

Biofilms tend to take hold in hot tubs and spas for two reasons. The first is that elevated temperatures make it a little more difficult to maintain proper sanitation levels. The second is that the water volume is much less and the bather load is much greater in a spa: jets promote skin exfoliation and heat promotes sweating.

The dead skin cells and bather introduced bacteria quickly deplete sanitizer levels. If this depletion is left unchecked, the bacteria and debris will eventually begin adhering to the internal plumbing, forming biofilms.

There are numerous products currently available to assist in removing biofilm, although many manufacturers hesitate to make that claim.

Biofilm is considered a “pest” by the EPA. Therefore, any product label that claims to prevent, destroy, or mitigate biofilm on a surface is a pesticidal claim that requires registration under FIFRA, including product efficacy data.

In other words, all spa cleaners are not created equally, and it’s essential to look for an EPA registration number if the goal is to kill biofilms.

Not many spa purges have EPA registration, but here are two that do: AHH-some, EPAReg No. 84409-1 and Hot Tub Serum, EPA Reg No. 844092. They are manufactured by Unique Solutions of Vero Beach, Florida.

It is important to take action to mitigate biofilms because they tend to harbor many common waterborne pathogens, protecting them from ordinary levels of disinfectant.

For example, Pseudomonas aeruginosa is a bacterium that thrives in warm water and can survive normal chlorination if it is protected by biofilm. It causes itchy skin, red rashes, and sometimes pus-filled blisters. Symptoms generally begin from 2 to 14 days after contact. Although most rashes clear up on their own, antibiotics are occasionally prescribed in severe cases or if an abscess develops.

Legionnaires’ Disease and the less severe Pontiac Fever are caused by the Legionella bacterium that is also harbored by biofilms. It is contracted by breathing contaminated aerosolized water. Pontiac Fever is experienced as a flu-like sickness while Legionnaires causes pneumonia that can be fatal in severe cases.

Nontuberculosis mycobacteria causes Hot Tub Lung, an inflammation of the respiratory tract. Like Legionnaires, it is contracted by breathing microdroplets of contaminated water. Symptoms include dehydration, stomach cramps, fever, nausea, and vomiting. Treatment includes a combination of antibiotics and sometimes surgery.

There are also a number of fecalrelated illnesses that can be contracted in hot tubs.

Cryptosporidium is one such parasite that can survive extreme levels of chlorination. Symptoms include dehydration, stomach cramps, fever, nausea, and vomiting. Killing it requires maintaining 20 ppm chlorine for at least 8 hours.

E. Coli is a bacterium that causes severe diarrhea with bleeding and abdominal cramps. Antibiotics are prescribed.

Giardia is one of the most common waterborne illnesses caused by a parasite that lives in human and animal intestines. It causes diarrhea, cramps, and nausea. Prescription drugs are given.

Hepatitis A is caused by a virus spread by contact with human feces. Symptoms include jaundice, fatigue, stomach pain, nausea, fever, and diarrhea. Treatment is bed rest and fluids. It may be fatal to those with compromised immune systems.

Norovirus is transmitted through oral contact with feces. Transmission through aerosolized water may also be a source. It can survive 10 ppm chlorine. The CDC reported that in 1997, three percent of cases were due to waterborne exposure. Symptoms include stomach cramps, nausea, vomiting, and fever. It generally clears up within 24 to 60 hours.

Shigellosis is a bacterial infection spread through contact with feces. It causes bloody diarrhea, fever, and stomach cramps. Treatment involves antibiotics.

In general, maintaining chlorine or bromine at industry-accepted levels will protect bathers from most of these pathogens. However, as stated in accompanying articles, cyanuric acid, the stabilizer found in dichlor and trichlor, will slow the disinfection process.

According to the Model Aquatic Health Code, there are a large number of references on the effect of CYA on microbial kill times (CT Inactivation Values). In general, they show that the presence of CYA increases CT inactivation values, and the amount of this increase depends on the pH and the ratio of CYA to available chlorine. However, there are few reports that relate specifically to the issue of what levels of available chlorine and CYA are required to maintain a swimming pool in a biologically satisfactory state.

Studies examining the effect of CYA on the disinfection capacity of chlorine show that using CYA or stabilized chlorine slows down the inactivation times on bacteria, algae, protozoa (Naegleria gruberi and Cryptosporidium parvum), and viruses (see accompanying table.)

Because cyanuric acid is known to slow chlorine’s kill speed against these pathogens, it is a good idea to keep levels within industry accepted guidelines – 30 to 50 ppm.

Kill rate of various pathogens with or without CYA