Proper Spa Management for Pool Pros Prevention of Legionellosis Outbreaks in Spas

What Conditions Increase Its Spread?

Water temperature between 77°F – 108°F causes rapid growth of this bacteria in spa water. Spa water which is not circulating for a period creates better environments for the bacteria to form in the biofilm in the spa plumbing lines, spa therapy jets and return lines. Decreased filtration and improper water chemistry can have some effect on the bacteria’s presence in the water. Scaling water conditions will increase the number of rough surfaces in the spa pipes, equipment, return lines and spa therapy jets, which bacteria can adhere to with buildup of biofilm. Filtration helps to remove sediment from the water, otherwise the bacteria can easily bind with these sediments in the water. If biofilms or amoebae are allowed to be present in the spa lines and equipment, then the bacteria can reside in this biofilm, or with the amoebae, in a perfect environment for it to survive. Lack of spa disinfection can also contribute to bacteria being present at sufficient levels to cause illness. High pH levels will decrease the percentage of active chlorine working in the water. This reduces its’ ability to kill this bacterium. High cyanuric acid levels will also prevent free chlorine in the water from disinfecting at its peak performance.

Legionella pneumophila Outbreak in Indian River County, FL

In 2016, I worked on an outbreak of two people infected with Legionella pneumophila from beginning to end, in a 55+ community in Indian River County, Florida.

How did the Health Dept. learn about it?

The people that were ill had visited either a local hospital or doctor’s office after developing pneumonia or other symptoms of Legionella. This resulted in the doctor’s office using a simple urine antigen test to determine if the antigen was present. This test is very simple and inexpensive compared to many other lab tests used to diagnose. If a patient is currently symptomatic with pneumonia and tests antigen positive, then doctors usually diagnose them with Legionella. The following step is for the doctor’s office or laboratory to report the results to the local health department since it is on the Reportable Diseases/ Conditions List for Florida.

What does the Health Dept. do with the Lab Results?

The local health department will not just sit on the result. Once received, it is assigned to a nurse or environmental health professional to contact the ill person and conduct a lengthy interview, involving specific questions regarding this bacterium to try and determine how the person became infected. In this instance, we found that both individuals used a public spa in the same 55+ community within the same week of each other.

What’s next for the Health Dept.??

The public spa, which is in common between the subjects, is then assigned to an environmental health pool inspector to conduct an inspection of that spa for risk factors that may exist, which could have contributed to the Legionella outbreak. Possible violations are notated on an inspection report and given to the property owner.

In this example, the spa was inspected and found to have no disinfectant level, a high pH level, their ORP controller was not operating properly, and there was no daily log of chlorine and pH levels.  These violations were notated, and the spa was immediately closed. Poorly maintained ORP controllers can contribute to many issues in the spa. ORP shall be maintained between 700-850 mV per Florida Dept. of Health.

Low ORP level & High pH level on ORP controller

The spa was reinspected and once all violations had been corrected, the spa was allowed to re-open.  A formal notice of violation was also issued to the property owner to alert them that if these violations existed during the next year, there would be fines imposed or further involvement by the Department of Health.

How was the Pool Pro Involved?

This public spa was serviced by an offsite licensed pool service contractor. The conditions found upon inspection were possibly due to negligence on the part of the pool service tech by not maintaining proper disinfectant levels, pH levels, operable ORP controller and current daily chemical log on the property.

Other Legal Issues….

There were other legal issues that this property had to deal with. The family of one of the ill persons obtained a lawyer and sued the property owner and the pool service company.

The lawyer issued a public records request from the Florida Dept. of Health for inspection records and other documents within specific time period that were relevant to this outbreak. They cannot obtain any medical records that would be protected by HIPPA.

In the end, it was found that the pool service company and property owner were both negligent due to improper maintenance of the public spa.  The property owner and pool service company both had to pay monetary damages to the family who filed the lawsuit.

What can a Pool Pro do to Control Legionella in their Public Spas?


A pool pro can maintain the following items to minimize the potential for Legionella outbreaks in public spas they service.
It is important that a pool pro treat all spas/hot tubs as having the potential for Legionella growth.

• Follow all manufacturer recommendations and local jurisdictional health agency requirements.
• Daily monitoring (recommend twice per day or hourly depending on use) of disinfectant and pH levels and record on chemical log.
  • Daily review of chemical logs and operating records for trends on disinfectant residuals or pH levels to indicate specific maintenance that needs to occur.
• Maintain proper disinfectant levels at all times
  Chlorine 3-10 ppm
  Bromine 4-8 ppm
• Maintain pH levels between 7.2-7.8
• Use of ORP to monitor disinfectant and pH levels and use automatic chemical feed to maintain these levels.
• Maintain cyanuric acid levels below 40 ppm so that chlorine is free to disinfect properly
• Maintain proper water balance to prevent scale & better % of chlorine working
• Run jet therapy pump daily for 15-30 minutes to ensure that chlorinated water is run through the therapy jet lines
• Backwash sand and diatomaceous earth (DE) filters routinely per manufacturer’s recommendations.
• Replace cartridge filter elements regularly per filter manufacturer recommendations.
• Ensure there is steady water movement across spa filter 24 hours per day.
• Post and enforce the maximum bather load from spa rules sign.
• Post rules on spa rules sign on appropriate use of the spa.
• Post spa signs with warnings regarding increased risk to those who are immune-compromised or chronic lung conditions/illnesses.
• Close spa daily to carry out disinfection of higher than allowed disinfectant residual per health code for at least 1-4 hours.:
  Free chlorine level of 10 ppm O
  10 times the combined chlorine level
• Drain, vigorously scrub, clean and disinfect spas walls, surfaces, tile and all holding tanks.
  Use 1:10 sodium hypochlorite to water solution that is freshly made for disinfection.
• Spa water ages, thus need to be replaced per equation:
  Water Replacement Frequency in days= Spa Volume /3/Average users per day
• Indoor spas/hot tubs should be in rooms with isolated air handlers and dehumidifiers. Locate building air handling system outlets and returns to reduce transmission.

These items should be of high importance to the pool pro and should be closely monitored. Prevention of this type of recreational water illness outbreak should be of the utmost importance, due to the possible legal and financial ramifications. I hope that the pool pros that read this article may think of their spas in a whole different way moving forward and learn how to keep the people using them from becoming ill.

Prevention Ideas

Many public health codes do not define spas as an increased risk aquatic venue. Even the CDC Model Aquatic Health Code, 2023 version defines it as:

“Increased Risk Aquatic Venue” means an aquatic venue which due to its intrinsic characteristics and intended users has a greater likelihood of affecting the health of the bathers of that venue by being at increased risk for microbial contamination (e.g., by children ages less than 5 years) or being used by people that may be more susceptible to infection (e.g., therapy patients with open wounds). Examples of increased-risk aquatic venues include spray pads, wading pools and other aquatic venues designed for children ages less than 5 years as well as therapy pools.

So, if microorganisms like Legionella pneumophila are present in spas/hot tubs and can cause serious health problems in our immune-compromised population, then why are they not considered at an increased risk aquatic venue?
It is my opinion, and you can take it as you read it here, but I think that spas should be recognized as an increased risk aquatic venues.

Once spas are recognized as an increased risk aquatic venue, then secondary disinfection requirements would be either highly recommended or required by local health authorities.

For example, Ultraviolet (UV) secondary disinfection systems have shown a Legionella inactivation dose rate to achieve 4-log inactivation is at 4 mJ/cm² .

UV secondary disinfection system can play a crucial role in spa water management for Legionella. Legionella, like many other microorganisms, are highly susceptible to UV disinfection. By utilizing UV for secondary disinfection and as a firewall, facilities could possibly reduce the incoming levels of these organisms into the spa water system. This dual disinfection approach, combining UV and chlorine disinfection, might ensure that these organisms are inactivated by UV before entering the spa water where our pool users are exposed. This combination of primary disinfection using chlorine along with secondary disinfection systems are highly recommended and used in Interactive Water Features, aka “splash pads.” Why not consider using this technology to reduce Legionella outbreaks in spas? This could possibly decrease outbreaks and fatal infection to our spa users. These and many other ideas are being looked at by public health staff across the country to reduce outbreaks like Legionella.