Toward the autonomous flushing of building plumbing: Characterizing oxidation-reduction potential and temperature...

Area of Science:

• Building water systems
• Water quality management
• Sensor technology

Background:

• Manual flushing is a common but inefficient method for addressing water quality issues caused by stagnant building plumbing.
• Sensor-based autonomous flushing offers potential for improved water management but faces knowledge gaps.
• Understanding disinfectant residual decay and sensor response is crucial for effective automated flushing.

Purpose of the Study:

• To evaluate the effectiveness of autonomous flushing in managing building plumbing water quality.
• To assess the utility of online oxidation-reduction potential (ORP) and temperature sensors for detecting water stagnation and optimizing flushing.
• To investigate the behavior of free chlorine and chloramine residuals under stagnation and flushing conditions.

Main Methods:

• Deployed online ORP and temperature sensor nodes in five residential kitchens for nine weeks.
• Collected data during winter and summer in homes using free chlorine and chloramine disinfectants.
• Conducted laboratory experiments to analyze ORP signals during chlorine decay and recovery.

Main Results:

• Online ORP sensors effectively detected free chlorine decay after overnight stagnation, which was mitigated by automated flushing.
• ORP sensors showed less consistent results for chloramine decay and delayed responses after disinfectant restoration.
• Temperature sensor-based flushing reduced flushing time by 46% compared to a fixed 5-minute duration.

Conclusions:

• Autonomous flushing, particularly using ORP sensors, can counteract water quality degradation in free chlorine systems.
• Temperature sensors offer a promising method for optimizing autonomous flushing duration and efficiency.
• Further research is needed to improve sensor responsiveness for effective control algorithms in diverse water chemistries.