Considerations for Large Building Water Quality after Extended Stagnation

Most of the world’s cities have been under some form of lock-down during the first few months of the global COVID-19 crisis. This means that many large (and small) buildings have been sparsely inhabited for periods of weeks or months. In many cases, drinking water supplies to those buildings will be lying dormant in pipes and storage tanks. This raises some important questions:

  • How might this affect water quality?
  • What are the public health risks?
  • How should building water supplies be managed during sparse population?
  • How should water supplies be re-commissioned as buildings are gradually repopulated?
  • What guidance is available for building managers and others to follow?

These questions are addressed in a forthcoming paper (currently available as a non-peer reviewed pre-print) titled “Considerations for Large Building Water Quality after Extended Stagnation”. This work was undertaken by a group of water quality researchers in the US and Canada, led by Prof Andrew Whelton at Purdue University.

The paper presents a synthesis of peer-reviewed, government, industry, and nonprofit literature relevant to the implications of water stagnation in plumbing systems and decontamination practices for water quality and health. Key concerns identified include:

A range of water management practices are canvassed for managing these potential impacts to water quality and public health for sparsely populated buildings. These include periodic flushing and, where water quality can’t be otherwise managed, full building closures.

Important considerations for building recommissioning (following a period of sparse occupation) are also provided. Possible actions include system flushing and the use of shock-disinfection. The importance of effective risk communication is also discussed.

A YouTube video describing this study is available at

The International Water Association (IWA) COVID-19 Task Force is currently planning a webinar panel to explore these issues further and provide the opportunity for questions. Keep an eye on this COVID-19 Waterblog for upcoming details.


Proctor, Caitlin, William Rhoads, Tim Keane, Maryam Salehi, Kerry Hamilton, Kelsey J. Pieper, David M. Cwiertny, et al. 2020. “Considerations for Large Building Water Quality After Extended Stagnation.” OSF Preprints. April 8.

Purdue engineering professor Andrew Whelton holds up a water sample from a building faucet. The pink color indicates the presence of chlorine, a disinfectant. Whelton’s team is investigating how water quality might change in buildings during a time of limited occupancy due to the COVID-19 pandemic. (Purdue University photo/Matthew Kerkhoff) 

Published by Stuart Khan

Professor of Civil & Environmental Engineering, University of New South Wales

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