23 Hospital Outbreaks. One Common Source: Wastewater Drains.
Key takeaway.
Across 23 outbreaks of carbapenem-resistant organisms in hospitals worldwide, wastewater drains were a consistent and recurring reservoir. Chemical disinfection repeatedly failed against drain biofilms. Physical barrier interventions showed the most consistent success.
The study.
This is one of the most comprehensive reviews of drain-associated infection outbreaks in the medical literature. Carling analyzed 23 published outbreaks of carbapenem-resistant organisms (CROs) - some of the most dangerous drug-resistant pathogens in modern healthcare - and found that wastewater drains were a consistent and often underappreciated reservoir for these organisms.
The paper examines the epidemiology of each outbreak, catalogs the interventions that were attempted, and evaluates their effectiveness. Across multiple countries, facility types, and pathogen species, the pattern was the same: pathogens established persistent biofilm colonies within drain systems, making them extremely difficult to eradicate with standard cleaning or chemical disinfection alone. Many facilities attempted chemical treatments, flushing protocols, or drain replacement with mixed and often temporary results.
The most important conclusion: studies that incorporated mechanical or physical barriers to prevent pathogen dispersal from drains demonstrated more consistent success than chemical-only approaches. The problem is not isolated. It is systemic. Drain-based transmission is a fundamental vulnerability in hospital plumbing infrastructure worldwide.
Key findings.
- Drains are a recurring source of outbreaks Across all 23 cases, hospital wastewater drains - including sink drains, floor drains, and shower drains - were identified as colonized reservoirs fueling ongoing transmission of carbapenem-resistant organisms to patients.
- Biofilm plays a central role Pathogens establish persistent biofilm colonies within drain systems, making them extremely difficult to eradicate with standard cleaning or chemical disinfection alone.
- Conventional interventions often fail Many facilities attempted chemical treatments, flushing protocols, or drain replacement with mixed and often temporary results. Even intensive bleach protocols showed limited durability against established drain biofilm.
- Physical barriers showed the most promise Studies incorporating mechanical or physical barriers to prevent pathogen dispersal from drains demonstrated more consistent success than chemical-only approaches.
- The problem is systemic, not isolated These outbreaks occurred across multiple countries, facility types, and pathogen species, indicating that drain-based transmission is a fundamental vulnerability in hospital plumbing infrastructure.
What this means for your facility.
Carling's review of 23 outbreaks across multiple countries and pathogen species confirms that drain-based transmission is not a theoretical concern or a rare edge case. With the CDC reporting over 680,000 healthcare-associated infections annually in U.S. hospitals and 1 in 31 patients affected on any given day, the problem Carling documents is massive and ongoing. Green Drain's product line covering 1.25-inch to 6-inch drains exists specifically to address this vulnerability. It provides a waterless, mechanical barrier between the contaminated drain system and the occupied space above.
A central finding is that chemical disinfection of drain biofilms fails because the biofilm is resilient and regrows. Green Drain's approach is fundamentally different: rather than attempting to kill pathogens inside the drain, the silicone one-way valve physically seals them off from the environment. The product does not need to defeat the biofilm. It contains it. Carling's 23-outbreak dataset is the peer-reviewed evidence behind this approach.
Carling found that physical barriers were among the most effective interventions. Green Drain's silicone one-way valve creates exactly this kind of barrier, and the product has been independently tested to verify it works. The SGS pathogen test (Report QDF25-0049810-01) showed the GD3 blocked over 99.9% of viral aerosols using the MS2 bacteriophage surrogate. The ASSE 1072-2020 life test (IAPMO Report 1554-25004) confirmed the GD4 maintained over 96% evaporation reduction even with debris obstruction, and over 99% with a clean seal, surviving 2,500 open-close cycles with no performance degradation. DTI odour tightness testing confirmed airtight performance at 200 Pa, with mechanical resistance over 700 Pa for most models.
For infection preventionists and hospital epidemiologists, these third-party validations combined with Carling's epidemiological evidence create a compelling, evidence-based case for specifying Green Drain in both new construction and retrofit applications. A systematic review of 23 outbreaks carries weight with specifiers. When an architect writes "barrier-type trap seal protection device per ASSE 1072" into a hospital specification, Carling's paper provides the clinical justification for why that line item matters.
Full citation.
Related research.
Protect your facility's drains.
Green Drain's waterless trap seal provides a mechanical barrier backed by independent testing. See how it works for your industry.