Bidet toilet seats with warm-water tanks: Residual chlorine, microbial community, and structural analyses

Toru Iyo, Keiko Asakura, Makiko Nakano, Mutsuko Yamada, Kazuyuki Omae

Research output: Contribution to journalArticlepeer-review

11 Citations (Scopus)


Despite the reported health-related advantages of the use of warm water in bidets, there are healthrelated disadvantages associated with the use of these toilet seats, and the bacterial research is sparse. We conducted a survey on the hygienic conditions of 127 warm-water bidet toilet seats in restrooms on a university campus. The spray water from the toilet seats had less residual chlorine than their tap water sources. However, the total viable microbial count was below the water-quality standard for tap water. In addition, the heat of the toilet seats' warm-water tanks caused heterotrophic bacteria in the source tap water to proliferate inside the nozzle pipes and the warmwater tanks. Escherichia coli was detected on the spray nozzles of about 5% of the toilet seats, indicating that the self-cleaning mechanism of the spray nozzles was largely functioning properly. However, Pseudomonas aeruginosa was detected on about 2% of the toilet seats. P. aeruginosa was found to remain for long durations in biofilms that formed inside warm-water tanks. Infectionprevention measures aimed at P. aeruginosa should receive full consideration when managing warmwater bidet toilet seats in hospitals in order to prevent opportunistic infections in intensive care units, hematology wards, and other hospital locations.

Original languageEnglish
Pages (from-to)68-80
Number of pages13
JournalJournal of Water and Health
Issue number1
Publication statusPublished - 2016 Feb


  • Bidet toilet
  • Microbial community
  • Pseudomonas aeruginosa
  • Residual chlorine

ASJC Scopus subject areas

  • Water Science and Technology
  • Waste Management and Disposal
  • Public Health, Environmental and Occupational Health
  • Microbiology (medical)
  • Infectious Diseases


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