From Sinks to Safety: Rethinking Drains in Healthcare
Introduction
In healthcare facilities, sinks are often viewed as clean zones, central to infection prevention and hand hygiene practices. However, a growing body of evidence suggests that the drains connected to these sinks may act as reservoirs for pathogenic microorganisms, including multi-drug resistant organisms. Drains are where we wash away contaminants, so it is logical that they are not sterile environments. Yet, the challenge arises when these contaminated spaces contribute to splash or aerosol transmission into clinical areas. Understanding the microbiology of drains, improving sink design, and adopting regular disinfection practices are crucial steps in mitigating these risks.
Why Drains Should Be Dirty, but Controlled
By function, drains receive contaminated fluids, cleaning residues, and organic matter. Over time, this mixture provides ideal conditions for biofilm formation. Once established, biofilms are difficult to remove and can harbor pathogens such as Pseudomonas aeruginosa, Klebsiella pneumoniae, and Acinetobacter baumannii (De Geyter et al., 2017). These microorganisms can persist and multiply within sink pipes and traps, creating a reservoir that is largely unseen but microbiologically active.
Drains should, in a sense, be “dirty,” since they perform the essential task of removing waste. However, they should not become unmonitored microbial ecosystems. In healthcare settings, where immunocompromised patients are common, even small environmental reservoirs can contribute to hospital-acquired infections (Kotay et al., 2017).
Evidence from Australia, New Zealand, and International Studies
Although much of the published research originates overseas, the risks associated with contaminated drains are directly relevant to healthcare environments in Australia and New Zealand. The Australian Guidelines for the Prevention and Control of Infection in Healthcare (2024) identify water systems, including sinks and drains, as potential sources of healthcare-associated pathogens. Hospitals in both countries frequently manage patients who are immunocompromised or critically ill, which increases the clinical significance of environmental reservoirs.
International studies consistently demonstrate that hospital drains can harbour Gram-negative organisms and act as a source of biofilm formation. De Geyter et al. (2017) reported that sink drains can become reservoirs of carbapenem-resistant Pseudomonas aeruginosa within tertiary-care facilities. Similarly, Hota et al. (2009) documented an outbreak of multidrug-resistant Pseudomonas aeruginosa linked to ICU sink traps, with genetic matching confirming the relationship between environmental and patient isolates.
There is also growing evidence that contaminated drains can contribute to bacterial dispersal beyond the plumbing system. Kotay et al. (2017) demonstrated that microorganisms within sink drain biofilms can disperse through droplets and aerosols during handwashing, with viable bacteria detected on nearby surfaces. Julian et al. (2018) further showed that splash and aerosol generation from handwashing sinks can transport microorganisms into the surrounding environment, highlighting the importance of sink design and drain management in preventing transmission.
Collectively, these studies underline the potential role of drains as active environmental reservoirs that may influence hospital microbiology and patient safety. Although country-specific studies in New Zealand are limited, the underlying mechanisms and risks apply to local facilities due to similar infrastructure, water system characteristics, and clinical workflows.
The Role of Sink Design and Aerosolisation
The design of sinks and plumbing systems plays a major role in how pathogens can spread from drains to clinical surfaces. Shallow basins, high-velocity faucets, and poor drain geometry can cause splashing, allowing droplets from contaminated drains to land on adjacent benches or even the hands of healthcare workers after handwashing (Julian et al., 2018).
Aerosolisation is another concern. When water hits the drain, turbulent flow can release microdroplets and aerosols containing bacteria from biofilm layers. These droplets may carry viable organisms that settle on surfaces within the patient zone. Over time, such exposure can lead to re-colonisation of the environment, undermining hand hygiene efforts. Addressing this issue requires an integrated approach that considers not just cleaning protocols, but also physical sink design, faucet flow rates, and drain structure.
The Need for Routine Drain Disinfection
Routine cleaning of sinks often neglects the drain itself. Even in well-maintained facilities, the internal surfaces of traps and pipes are rarely disinfected because they are difficult to access. As a result, biofilms can persist even when external surfaces appear clean. This presents a challenge for infection prevention programs that focus primarily on visible cleanliness.
A systematic approach to drain disinfection can reduce the microbial load within plumbing and minimize the potential for aerosolisation. Some hospitals employ thermal flushing or oxidising agents to treat drains, but these methods can be labour-intensive or impractical for frequent use. Chemical disinfection using oxidising compounds, particularly those that can generate a foaming action, has emerged as a practical method to penetrate the upper drain and trap area.
Why Peracetic Acid is Suitable for Drain Applications
Peracetic acid (PAA) is a strong oxidising agent with broad-spectrum antimicrobial activity against bacteria, fungi, spores, and viruses. Its decomposition products, acetic acid and oxygen, make it relatively environmentally benign compared to chlorine-based disinfectants. Research indicates that PAA can disrupt and penetrate biofilms more effectively than some quaternary ammonium compounds or hypochlorite solutions (Marchetti et al., 2018).
When applied as a foaming agent or powder that reacts with water to generate foam, PAA can reach the complex surfaces of sink drains and traps. The foam adheres to surfaces long enough to provide contact time for microbial inactivation. This approach offers a practical solution for periodic disinfection of drains without the need for invasive maintenance or pipe disassembly.
Implementation in Healthcare Settings
Healthcare facilities can adopt a structured program for drain disinfection that includes:
Identifying high-risk areas such as intensive care units, oncology wards, and procedure rooms.
Establishing a disinfection schedule, such as weekly or fortnightly, using a validated foaming disinfectant protocol.
Incorporating drain disinfection into the environmental cleaning policy alongside surface cleaning and water safety management.
Educating environmental services staff on correct preparation, contact time, and safety precautions.
Periodically reviewing microbiological testing results or drain swab cultures to assess effectiveness.
A coordinated approach ensures that drain management becomes a routine part of infection prevention rather than a reactive response to contamination events.
The Case for New Zealand Healthcare
New Zealand hospitals face similar risks to their Australian counterparts. Many healthcare facilities in both countries were built before modern infection-prevention design standards were established. Retrofitting entire plumbing systems may be impractical, making routine drain disinfection a pragmatic interim measure.
Given the emphasis on hand hygiene within national quality frameworks, it is paradoxical that the very drains beneath those sinks receive limited attention. Integrating periodic disinfection into infection-control practices can strengthen the overall hygiene chain and reduce the potential for environmental reservoirs to contribute to transmission.
Conclusion
Drains are a necessary part of every healthcare facility. They are meant to be dirty because they carry away contaminants, but they should not serve as hidden reservoirs for pathogens. Evidence from Australia, New Zealand, and international studies demonstrates that poorly managed drains can harbor biofilms and release bacteria through splash and aerosolisation. Improving sink design and implementing regular disinfection programs are practical, evidence-based measures to reduce these risks.
Foaming disinfectant powders that can be poured directly into drains represent an emerging and effective way to target microbial reservoirs at their source. By applying such measures, healthcare facilities can close a gap in environmental hygiene, strengthen infection-prevention efforts, and contribute to safer patient care environments.
References
Australian Commission on Safety and Quality in Health Care. (2024). Australian guidelines for the prevention and control of infection in healthcare (version 11.22). https://www.safetyandquality.gov.au/
De Geyter, D., Blommaert, L., Verbraeken, N., Janssens, A., Vandoorslaer, K., De Boeck, K., De Baets, F., & Malfroot, A. (2017). Sink drains as reservoirs of carbapenem-resistant Pseudomonas aeruginosa in a tertiary care hospital. American Journal of Infection Control, 45(1), e1–e3. https://doi.org/10.1016/j.ajic.2016.10.013
Hota, S., Hirji, Z., Stockton, K., Lemieux, C., Dedier, H., Wolfaardt, G., & Gardam, M. A. (2009). Outbreak of multidrug-resistant Pseudomonas aeruginosa colonization and infection secondary to imperfect intensive care unit sink traps. Infection Control & Hospital Epidemiology, 30(1), 25–33. https://doi.org/10.1086/592700
Julian, T. R., Leckie, J. O., & Boehm, A. B. (2018). Splash and aerosol generation by handwashing sinks and implications for infection control. Journal of Hospital Infection, 100(4), e210–e215. https://doi.org/10.1016/j.jhin.2018.07.018
Kotay, S. M., Chai, W., Guilford, W., Barry, K., & Mathers, A. J. (2017). Spread from the sink to the patient. Applied and Environmental Microbiology, 83(8), e03327-16. https://doi.org/10.1128/AEM.03327-16
Marchetti, R., Arghittu, A., & Lupi, E. (2018). Effectiveness of peracetic acid against bacterial biofilms in laboratory models and industrial environments. International Journal of Hygiene and Environmental Health, 221(2), 283–291. https://doi.org/10.1016/j.ijheh.2017.12.001
