Sensor Taps or Traps?

A recent journal article has highlighted a potential health risk associated with sensor taps in buildings. The study conducted by Public Health England researchers identifies a problem that has not previously been reported.

An experiment was conducted to help in the investigation of hospital sensor taps and effects of microbial colonisation on internal components. Pseudomonas aeruginosa was introduced into this controlled experiment by injection into 27 sensor tap assemblies. Subsequently the taps were flushed and monitored over a two year period and results recorded. Finally sensor taps were dismantled and colonisation of the diaphragm rubber by the P. aeruginosa bacteria was evident.

Below photo of experiment – (Moore et al 2016)




When Johns Hopkins staff were testing how often their water system needed to be flushed, they were surprised to discover Legionella growing in 50% of the cultured water samples from 20 hands-free taps, compared to 15% in samples from 20 manual faucets in the same areas’.

While Legionella poses little risk to healthy individuals, it can cause serious infections in people with weak immune systems. This is true for a range of bacteria commonly isolated from hot, cold and warm water systems in buildings.

Below is an example of a rubber sensor tap diaphragm with bacterial colonisation.



The experimental results indicated that the solenoid valve rubber diaphragm harboured more bacteria in biofilms than manual fauctes without a solenoid valve. Routine maintenance and disinfection of the sensor taps of the fittings resolved the problem (see diagram below).





The EnHealth Guidelines for Legionella control support these results. The guidelines recommend avoiding dead legs and areas of low flow. As shown above sensor taps may increase the risk of Legionella due to poor water flow. The plastic components also provide surfaces for biofilm growth and Legionella proliferation. Sensor tap components need maintaining, cleaning and disinfectiond on a regular basis to minimise legionella growth risks as part of a Water Risk Management plan.

Fixing the Problem

Hindmarsh Water Treatment has identified facilities with issues with sensor taps including major hospitals and aged care facilities. In one premises positive counts of legionella  were returned from sensor taps located in the building corridors on numerous occasions. However this problem was overcome by replacing them with normal basin mixers. Also installation of 0.22 micron (Pall) filters on tapware and Sensor taps in the ICU can reduce the risk in other settings. Another solution has been installation of point of entry filtration and disinfection and ensuring weekly flushing takes place to control the problem.


Nevertheless if you need assistance answering these questions Hindmarsh Water Treatment are ready to assist.

Further reading

Moore et al (2015) Biofilm formation in an experimental water distribution system: the contamination of non-touch sensor taps and the implication for healthcare. Biofouling 31(9-10):677-87

Department of Health, EnHealth (2015) Guidelines for Legionella control in the operation and maintenance of water distribution systems in health and aged care facilities.