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

Ernesto F Martinez Paz; Lutgarde Raskin; Krista R Wigginton; Branko Kerkez

doi:10.1016/j.watres.2023.121098

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

Water Res. 2024 Mar 1:251:121098. doi: 10.1016/j.watres.2023.121098. Epub 2023 Dec 31.

Authors

Ernesto F Martinez Paz¹, Lutgarde Raskin¹, Krista R Wigginton², Branko Kerkez³

Affiliations

¹ Department of Civil and Environmental Engineering, University of Michigan, 2350 Hayward Ave., 2044 GG Brown, Ann Arbor, MI 48109, USA.
² Department of Civil and Environmental Engineering, University of Michigan, 2350 Hayward Ave., 2044 GG Brown, Ann Arbor, MI 48109, USA. Electronic address: kwigg@umich.edu.
³ Department of Civil and Environmental Engineering, University of Michigan, 2350 Hayward Ave., 2044 GG Brown, Ann Arbor, MI 48109, USA. Electronic address: bkerkez@umich.edu.

PMID: 38219686
DOI: 10.1016/j.watres.2023.121098

Abstract

Manual flushing of building plumbing is commonly used to address water quality issues that arise from water stagnation. Autonomous flushing informed by sensors has the potential to aid in the management of building plumbing, but a number of knowledge gaps hinder its application. This study evaluates autonomous flushing of building plumbing with online sensor and actuator nodes deployed under kitchen sinks in five residential houses. Online oxidation-reduction potential (ORP) and temperature data were collected for nine weeks during the winter and summer in houses with both free chlorine and chloramine. ORP levels in houses with free chlorine residuals decreased after overnight stagnation. The overnight decrease in ORP was not observed when tap water was automatically flushed for five minutes at 6:00 h every morning. ORP levels in houses with chloramine residuals did not decrease consistently after overnight stagnation, and daily automated flushes did not have an observable effect on the ORP signals. Additional laboratory experiments were carried out to evaluate ORP signals during chlorine decay and after incremental changes in chlorine, as would be expected in building plumbing conditions. Results from the lab and field deployments suggest on-line ORP sensors may be used to detect free chlorine decay due to stagnating water, but are not as effective in detecting chloramine decay. However, field results also suggest ORP may not respond as expected on a timely manner after free chlorine or chloramine have been restored, hindering their applicability in developing control algorithms. In this paper we tested twice-daily five-minute automatic flushing and found that it counteracts water quality degradation associated with overnight stagnation in free chlorine systems. An automatic sensor-based flushing is proposed using online temperature sensor data to determine when flushing has reached water from the main. The results suggest that flushing informed by temperature sensors can reduce the flushing time by 46 % compared to the preset five-minute static flush.

Keywords: Chloramine; Chlorine decay; Drinking water; Free chlorine; ORP; Premise plumbing.

MeSH terms

Chloramines
Chlorine
Drinking Water*
Oxidation-Reduction
Sanitary Engineering*
Temperature
Water Supply

Substances

chloramine
Chloramines
Chlorine
Drinking Water