Biofilm Development and Opportunistic Pathogen Proliferation in Domestic Shower Hoses

Flexible plastic shower hoses typically experience long water stagnation times and high-water temperatures, and the hoses themselves can leach organic matter. This makes them susceptible to biofilm formation and opportunistic pathogen (OP) proliferation. However, no past research has systematically studied the effect of chlorine and stagnation time on biofilms and OP proliferation. I conducted three studies to address the impact of chlorination and stagnation time on biofilm formation and OP proliferation in shower hoses. In the first, existing (“old”) shower hoses were collected from homes with either chlorinated or non-chlorinated water sources. In the second study, I installed new shower hoses in homes and monitored biofilm development and OP formation over five months. Finally, in the third study I built experimental shower hoses in the lab and operated them with carefully controlled chlorine concentrations and stagnation times. These also were operated for five months. Results from the three studies suggest that chlorine slows biofilm formation and OP proliferation but does not stop them. Shorter stagnation times increase biofilm formation rates in non-chlorinated systems but decrease them in chlorinated systems.