Purpose

This project was initiated in response to the Coronavirus disease (COVID)-19 pandemic. The explosive onset of school, business, and event venue closings across the nation prompted global questions about water safety. Would the water be safe to use when the buildings were reopened? What about the safety of the people inside these low water use buildings? The lack of national and industry guidelines for building reopening -as it related to water safety- inhibited clear building operation and management decisions that were protective of public health.

Approach

Several studies were conducted to determine how extended water stagnation impacted cold and hot water safety. This study explored water quality inside school, office, and institutional buildings that were shutdown. Water was screened for chemicals like heavy metals (copper, lead, manganese, etc.). Water was also tested for disease-causing microorganisms like Legionella. For a more controlled environment, the impact of stagnation time on water quality was tested in four identical plumbing laboratory setups. Water softeners were also purchased from a major plumbing supplier and were tested.

Discoveries

GENERAL: The lack of official universal U.S. and industry plumbing flushing procedures and the scientific understanding about how to create those procedures prompted public health concerns nationwide. In the course of this project, the team found that building owners generally wanted to reduce the chance that unsafe water reached people in their buildings. Due to the lack of guidance available, some building owners haphazardly flushed fixtures, with no measurable sustaining improvement on water quality. For buildings that had hundreds of faucets, owners often did not have the labor required to conduct a complete building flush or repeated flushing.

IN BUILDINGS: When water was tested in buildings that had been closed for months, heavy metals like copper, lead, manganese, and nickel sometimes exceeded safe limits, but widespread contamination (at every fixture in every building) was not found. To address these issues, one recommendation to building owners was to flush fixtures before reopening. Though, flushing by contractors hired by one building owner caused scale destabilization and increased heavy metal levels temporarily until flushing was completed. To reduce heavy metal contamination, there was no "one size fits all" flushing time that worked for all fixtures in a single building (or across buildings). For example, in one building flushing 5 minutes resulted in detectable chlorine residual to the faucet in 3 buildings, while no residual chlorine was detected even after 125 minutes of flushing in the largest and oldest building of that study. Building owners should design flushing procedures based on the actual design of their plumbing, and this type of protocol can be required during building commissioning.

Screening water for the pathogen Legionella pneumophila was a primary focus in this project. This organism was detected in some building water systems. Legionella was detected not just in hot water, but was also found in cold water (i.e., water fountains, etc.). While some organizations had recommended shock disinfection to reduce the levels of this organism in plumbing, this project found that sometimes flushing alone was effective. For one building, a private company conducted shock disinfection and Legionella was detected immediately after disinfection. This detection was likely due to the organisms being released from biofilm during the aggressive flushing process. Legionella was not detected weeks later from that plumbing. No national or industry protocols were found that determined what metrics were most important determining plumbing disinfection effectiveness.

WATER SOFTENERS: New drinking water softeners were found to leach excessive levels of carbon and sulfur into drinking water, and potentially microplastics. These discoveries underscore the need for the devices to be thoroughly flushed before use. Softeners were also found to be susceptible to hydrocarbon chemical. Once contaminated, the softener resin still leached hydrocarbons more than 2 weeks after the flush-out.

MOCK PLUMBING SYSTEMS:  For 6 months, four full-scale plumbing setups underwent weekly flushing, daily flushing, and intermittent flushing. Testing revealed that chlorine residual, meant to minimize microorganism growth in plumbing, was rarely present in stagnant samples. Regular weekly flushing was not sufficient to minimize microorganisms growing in the plumbing. Legionella spp. was found and most often positive when weekly flushing was used. The working conclusion is that only the daily plumbing flushing action controlled microorganism levels.

Knowledge Sharing

Results were shared publicly through websites, social media, interviews with TV, radio, and other media. The project team responded directly to building owners, health officials, and inhabitants (i.e., parents of school children) who requested information about water safety in buildings. Studies were under review by scientific journals at the time this report summary was created. Once approved, links to the studies will be available at https://www.PlumbingSafety.org. Results were presented at more than 50 events hosted by building construction, public health, plumbing technology, engineering, and green building organizations, and university seminars and symposiums.

Last Modified: 05/03/2023
Modified by: Andrew J Whelton