legionella-shower-head

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A legionella shower head question usually starts with a simple worry: can the water coming out of a shower head carry Legionella bacteria into the lungs? The two studies covered here say the shower hose and the tubing behind the head can hold Legionella in a slimy layer of microorganisms called biofilm, and that shower aerosols are a known route of exposure. Neither study measured illness in people using home showers, so the answer to how much risk is not in these sources.

Quick answer

• A 2015 laboratory model found Legionella in the biofilm on flexible shower tubing, at a maximum of “2.0 × 10 3 copies/cm 2 of PVC tubing” in that model.
• The same model found no significant difference between tubing that dried between uses and tubing that stayed wet, so the authors conclude that allowing shower tubing to dry between uses “will not reduce the risk for Legionella or MAC colonisation.”
• A 2023 study of 85 shower hoses from one building reported Legionella at relative abundances from 0 to 7.8 percent of the biofilm bacteria, with L. pneumophila at 0 to 0.46 percent.
• Neither study gives a cleaning method for Legionella. The sources do not say how to remove Legionella from a shower head.

What the 2015 model study did

Whiley, Giglio and Bentham built a model potable warm water system that used thermostatic mixing and a flexible shower head, “as typically found in hospitals aged care facilities and domestic households.” The model used PVC flexible tubing with an internal diameter of 10 mm. Water was held at 35 °C and pumped at 9 litres per minute, for 3 minutes a day on five days, with two days off. The authors ran this for six weeks to let the biofilm establish before they began sampling.

Two sections of tubing were compared. One stayed filled with water between uses, and the other drained dry between uses. The authors describe this as representing “a flexible shower head left on its hook” Sampling used swabs taken from the pipe surface, not from the water, so the results describe the biofilm layer on the tubing.

The study reports the highest levels it found: MAC at 7.0 × 10 4 copies/cm 2 and Legionella at 2.0 × 10 3 copies/cm 2 of PVC tubing. These are gene copies measured by qPCR. The authors note that “qPCR does not differentiate between viable and killed cells”, so a qPCR result does not show whether the bacteria could grow. They argue that colonisation of the biofilm “indicates viability” but this is an inference from the method.

The model used water that was not spiked with positive cultures. The authors state that the South Australian potable water in the model “was not spiked with positive cultures” and they suggest that Legionella and MAC were present in the local supply. That point is about one water supply in one city, so it should not be read as a national finding.

What the 2023 hose study did

Cavallaro and colleagues took 85 shower hoses out of service, all from the same manufacturer, of similar age, and fed from the same building plumbing. The abstract calls the building a “multiunit residential building” while the methods section says “Samples were collected from a retirement facility in Switzerland.” The two descriptions do not match, and the sources checked do not explain the difference, so this guide reports the setting as the sources describe it.

The team extracted the biofilm by filling each hose with glass beads and water, sonicating them, and then concentrating the material. They measured Legionella with digital droplet PCR and profiled the wider bacterial and eukaryotic community with amplicon sequencing. The paper reports that Legionella spp. “were present at values between approximately 1E+3–1E+7 GU/hose.” It also says that “Legionella spp. relative abundance in the biofilms ranged between 0–7.8%, of which only 0–0.46% was L. pneumophila”

The authors note a limit that matters for home readers. They write that “no specific information on use habits (e.g. frequency, temperature, etc.) could be obtained due to privacy protection concerns.” The study cannot say how often a hose was used, how hot the water ran, or how long water sat in the hose between showers. Those are the conditions that the 2015 model tried to copy.

How showers expose people to Legionella

Both sources describe the same route of exposure. The 2015 paper states that organisms in shower biofilm are “dispersed into the passing water and aerosolised by the showerhead, providing means for inhalation deep into the respiratory tract” The 2023 paper says that “Shower hoses have been previously linked to the transmission of Legionella through inhalation of water aerosol containing the bacteria” and that shower hoses “ranked second in a relative ranking of Legionella exposure pathways from common household water uses” That ranking comes from a 2014 study the 2023 authors cite. It was not opened for this guide, so it is reported here only as the 2023 paper describes it.

The 2023 paper also states that “In a few cases, showers have been directly linked to Legionellosis transmission, specifically in nursing homes, hospitals and hotels” and it adds that “limited information regarding showers as route of transmission is overall available.” Both points are useful for calibration. Shower-linked cases are documented, but the sources do not give a count of how often they happen.

The 2015 paper cites a US estimate that “8000 to 18,000 people contract Legionnaires’ disease annually,” and notes that “less than 10% of estimated cases are reported to local and state health officials” That estimate is for the whole country and for all sources, not for showers.

Who the sources say is at higher risk

The sources do not give a risk ranking for Legionella by age, immune status, or lung health. What they do say is where shower-linked infections have been reported: nursing homes, hospitals, and hotels. The 2015 paper also says that studies of nosocomial outbreaks “have identified contamination of hospital water distribution systems” and “specifically shower heads as a likely source of infection” Nosocomial means hospital-acquired.

The 2015 paper makes a separate point about Mycobacterium avium complex (MAC), which is a different organism. It lists lung disease among MAC illnesses, including “fibrocavitary lung disease” and “fibronodular bronchiectasis” and it notes “disseminated infection in immune compromised patients” It also reports that the prevalence of MAC in bathrooms “of patients with pulmonary MAC was significantly higher than that in healthy volunteers’ bathrooms” These are findings about MAC, not Legionella, and they do not show the same risk pattern for Legionella.

If you have a weakened immune system, a chronic lung disease, or you are caring for someone who does, talk to a doctor about water exposure before you change your shower routine. This guide does not give medical advice, and the sources do not say which precautions a doctor would recommend.

What the sources do not say

• The sources do not give a cleaning or disinfection method for a shower head or hose. The 2015 model studied drying and flushing only. The 2023 study looked at the community living in hoses, not at treatments.
• The sources do not examine chlorine, heat, or any other treatment against Legionella in a shower hose.
• The 2015 model found that once-a-day flushing did not remove the biofilm. The authors write that the flushing “did not provide sufficient shearing force to remove biofilm or prevent its formation” That is a finding about one flushing schedule, not a treatment guide.
• The sources do not say how often a shower head should be replaced, or whether a particular material is safer. The 2023 paper notes that the sampled hoses came from one manufacturer and one material.
• The 2023 hoses were fed with “non-chlorinated drinking water” The sources do not say what happens in a home where the water is chlorinated, or whether chlorine changes the result.

How we chose

This guide uses two peer-reviewed journal articles, both available as open-access texts and both opened on 2026-10-28. The 2015 paper was chosen because it is the only source checked that measures Legionella in shower tubing and tests the drying question directly. The 2023 paper was chosen because it measures Legionella in real shower hoses, not in a model, and it reports the abundance figures and the study’s limits. Both are research papers, not product pages, and no product is recommended here.

The studies do not agree on everything. One calls the 2023 setting a residential building and the other a retirement facility. The guide reports both descriptions and does not choose between them.

What we could not verify

• Whether the 2015 model reflects a home shower. The model used a fixed temperature and flow, and a non-continuous pattern of use that the authors say is likely for hospital showers.
• Whether the 2023 hoses reflect the hoses in other buildings. The sample is from one building, one manufacturer, and an unknown pattern of use.
• Whether the Legionella detected by qPCR was able to cause infection. The 2015 paper states the method does not separate viable from dead cells.
• The Hines et al. 2014 ranking of exposure pathways. It is cited in the 2023 paper, but the source was not opened for this guide.

FAQ

Can a shower head carry Legionella?

Both studies found Legionella in the biofilm of shower tubing or hoses. The 2015 paper found it on PVC tubing in a model, and the 2023 paper found it in hoses taken from a building. Neither study shows whether a particular shower head caused a particular illness.

Does drying a shower head stop Legionella?

The 2015 model found no significant difference between tubing that dried between uses and tubing that stayed wet. The authors conclude that allowing shower tubing to dry between uses “will not reduce the risk for Legionella or MAC colonisation.” This is one model, so it is evidence against drying as a fix, not proof about every home.

Is a shower the main way people get Legionella?

The sources do not say. The 2023 paper cites a ranking that puts shower hoses second among household water uses. It also notes that “limited information regarding showers as route of transmission is overall available.”

Which people are at higher risk from shower-linked Legionella?

The sources do not give a risk ranking for Legionella by age or immune status. They name nursing homes, hospitals and hotels as settings where showers have been linked to transmission. If you have a weakened immune system or lung disease, talk to a doctor.

What cleaning method do the sources recommend?

None. The sources checked give no cleaning method for Legionella in a shower head. Do not treat this guide as a cleaning protocol.

Do the studies show what the water temperature should be?

The 2015 model held water at 35 °C to represent thermostatic mixing. The sources do not compare temperatures or recommend a setting for home water heaters.

Bottom line

The two studies show that Legionella was detected in the biofilm on shower hoses and tubing, and that drying a hose between uses did not reduce it in the model. They do not show how often shower-linked illness happens, and they do not give a cleaning method. For anyone with a weakened immune system or lung disease, the first step is a conversation with a doctor.

Sources

• Whiley H, Giglio S, Bentham R. “Opportunistic Pathogens Mycobacterium Avium Complex (MAC) and Legionella spp. Colonise Model Shower” Pathogens. 2015;4(3):590-598. https://pmc.ncbi.nlm.nih.gov/articles/PMC4584274/ (opened 2026-10-28)
• Cavallaro A, Rhoads WJ, Sylvestre E, et al. “Legionella relative abundance in shower hose biofilms is associated with specific microbiome members” FEMS Microbes. 2023;4:xtad016. https://pmc.ncbi.nlm.nih.gov/articles/PMC10496943/ (opened 2026-10-28)