A recent journal article has highlighted a potential health risk associated with sensor taps in buildings. The study conducted by Public Health England researchers has identified 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. In this research Pseudomonas aeruginosa was introduced into a model water system by injection into 27 sensor tap assemblies. Taps were flushed and monitored over a two year period and results recorded. At the end of the experiment, 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 colonising hot, cold and warm water systems in buildings.

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



Experiment conducted with results outlined and the solenoid valve rubber diaphragm harboured bacteria in biofilms compared to manual faucets without a solenoid valve. The study shows that routine maintenance and disinfection of the sensor taps of the fittings will resolve the problem (see diagram below).





The EnHealth Guidelines for Legionella control further supports these results. These guidelines advocate that dead legs and areas of low flow should be avoided. In support of this sensor taps increase the risk of Legionella due to poor water flow. The plastic components also provide surfaces for biofilm growth and Legionella proliferation.

As part of a Water Risk Management plan you should ensure all relevant sensor tap components are maintained, cleaned and disinfected on a regular basis to mitigate legionella growth risks.

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


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.