Infection prevention and control (IPC) programmes in Croatian hospitals concentrate on surfaces, hands and equipment sterilisation. Floor drains are rarely part of the standard protocols. Yet 12 peer-reviewed studies in the international literature link precisely those drains to reservoirs of Pseudomonas aeruginosa, Klebsiella pneumoniae and NDM-producing organisms.
What the literature says
A study published in the Journal of Hospital Infection (2019) followed eight ICUs over 18 months. 78% of hospital-acquired Pseudomonas aeruginosa colonisations in patients were a genetic match for strains isolated from the local floor drains. In other words — patients were being colonised by strains that were already in the room, in the biofilm of the drain.
A review in Clinical Microbiology Reviews is devoted specifically to sink drain-related healthcare-associated infections and to the approaches used to decontaminate them.
Aerosolisation is the primary mechanism — droplets formed as water enters the drain lift micro-organisms 30–50 cm above floor level. That is enough to colonise bed legs, wheelchair rims or the hands of a patient in a shower chair.
What lives in a hospital drain
Floor drains and washbasin traps carry a biofilm containing the very pathogens the IPC team is working to eliminate elsewhere in the building:
- CRE — carbapenem-resistant Enterobacteriaceae. Klebsiella pneumoniae, Enterobacter cloacae, NDM-1 producers. In several documented outbreaks in European and US hospitals the drain was the source.
- Pseudomonas aeruginosa — survives indefinitely in trap biofilm and is lifted on aerosol whenever water is run.
- Stenotrophomonas maltophilia — a common drain coloniser on cystic fibrosis and oncology wards, resistant to most empirical antibiotics.
- MRSA and VRE — secondary colonisation in drain runs shared between rooms.
The chain is the same in every report: biofilm establishes in the drain elbow, ordinary flow disturbs it, aerosol lifts the organisms above floor level, surfaces near the patient become contaminated, the patient becomes colonised, and only then does clinical infection follow.
Why disinfectants do not solve it
Standard disinfection protocols (chlorine, quaternary ammonium compounds, peracetic acid) act on surface micro-organisms. Biofilm — the gel matrix of polysaccharides that the bacteria synthesise — shields the population underneath.
- 5% chlorine reduces the surface population by more than 99% in 60 seconds
- The same concentration penetrates less than 0.5 mm into biofilm
- The population regenerates to pre-treatment levels within 24–48 hours
- Antibiotic resistance inside the biofilm is passed to new strains via plasmids
Why IPC programmes overlook drains
A standard audit tracks hand hygiene, central line bundles, surgical site preparation and surface disinfection. All of those are correct measures, but the drain is treated as plumbing infrastructure rather than as part of the patient environment. Three reasons the gap persists:
- Sampling is difficult. A swab does not reach the deeper layers of the matrix, and sonication of drain components is not workable in routine surveillance.
- No agreement on the intervention. Chlorine does not penetrate biofilm, hot water flushing generates aerosol, and chemical treatments have no proven sustained effect. The estates team and the IPC team describe the same problem in different vocabularies.
- No guidance dedicated to drains. The CDC's water-management guidance for healthcare facilities explicitly addresses sinks and drains as a transmission route for multidrug-resistant organisms. In Croatian practice drains are not specifically covered in IPC protocols, so each institution interprets the international sources on its own.
The mechanical barrier and the test data
A silicone one-way seal works mechanically, not chemically. The membrane opens under the weight of the water and closes when the flow stops, cutting the aerosol path into the room. The biofilm stays in the pipe, but it no longer reaches the ward.
Independent SGS testing (report QDF25-0049810-01) confirmed blockage of more than 99.9% of viral aerosols using MS2 bacteriophage as the surrogate. ASSE 1072-2020 certification confirms more than 2,500 cycles under IAPMO 1554-25004 testing — roughly five years of typical hospital use.
What implementation looks like in a hospital
A typical implementation plan in a Croatian general hospital:
- Mapping — an inventory of every floor drain by risk zone (theatres, ICU, general wards, washrooms, kitchen, service corridors)
- Sizing — a measuring tool identifies the size of each trap (from 1.25" to 6")
- Pilot — typically one floor or department over 30–60 days, with microbiological monitoring before and after
- Rollout — extension across the whole facility
- Documentation — recording serial numbers in the CMMS, with an annual visual inspection
Croatian hospitals that have run pilot programmes report a reduction of more than 90% in odour incidents in washrooms, and drain fly populations in kitchen zones falling to practically zero.
What procurement should ask for
When assessing tenders for floor drain seals, ask for:
- An independent aerosol blockage report (SGS or equivalent)
- Life-cycle certification to ASSE 1072 or equivalent
- NSF/ANSI 2 material safety certification
- HACCP International approval, where the hospital kitchen is brought into the same programme
Green Drain™ holds all four. Most competing products satisfy one or two of them and are mis-specified for hospital procurement.
Full overview: Green Drain™ — how a passive one-way drain seal works — sizes, materials, certification and how it is used in hospitals, hotels, schools and homes.