Analysis of building plumbing system flushing practices and communications

Drinking water distribution system contamination incidents can prompt public agencies and drinking water utilities to issue do-not-drink and do-not-use advisories. After the contaminant is cleared from distribution mains, consumers are often directed to flush their plumbing. However, little validated guidance and few evaluated communications strategies are available on using flushing to decontaminate building water systems. Additionally, limited data support the effectiveness of current practices and recommendations. In this study, expert elicitation was used to assess existing flushing guidance and develop validated flushing guidance and communications for single-family residences. The resulting guidance recommends progressively opening all cold-water taps from the closest to point of entry to the furthest and allowing the water to run for at least 20 minutes. Hot-water taps should be opened progressively and run for at least 75 minutes. The guidance language and format conformed to grade-level and readability scores within recommended health communication ranges. The readability of eight other flushing guidance documents was also evaluated for contamination incidents from 2008–2015. Seven were written at a 10th–12th grade level, above the 6th–7th grade level recommended for health communications. This is an Open Access article distributed under the terms of the Creative Commons Attribution Licence (CC BY 4.0), which permits copying, adaptation and redistribution, provided the original work is properly cited (http://creativecommons.org/licenses/by/4.0/). doi: 10.2166/wh.2019.024 om http://iwaponline.com/jwh/article-pdf/17/2/196/845968/jwh0170196.pdf 2022 Lisa Ragain Metropolitan Washington Council of Governments, 777 North Capitol St NE #300, Washington, DC 20002, USA Sheldon Masters (corresponding author) Timothy A. Bartrand Corona Environmental Consulting, LLC, 4012 Ridge Avenue, Philadelphia, PA 19129, USA E-mail: smasters@coronaenv.com Jennifer L. Clancy Environmental Science, Policy and Research Institute, 4012 Ridge Avenue, Philadelphia, PA 19129, USA Andrew J. Whelton Division of Environmental and Ecological Engineering and Lyles School of Civil Engineering, Purdue University, 550 Stadium Mall Drive, West Lafayette, IN 47907-2051, USA This article has been made Open Access thanks to the generous support of a global network of libraries as part of the Knowledge Unlatched Select initiative.


INTRODUCTION
In the USA and Canada, water chemical contamination incidents that occurred between early 2014 and mid-2015 affected more than 1 million people and resulted in more than 150,000 building water systems being contaminated by a variety of organic contaminants (Casteloes et al. ). Contaminant fate and transport in building plumbing can differ widely based on the plumbing system material, plumbing system configuration and contaminant, with some contaminants posing risks to building water systems (BWS)  Adding to the complexity, building plumbing and the distribution system supplying water to BWS comprise a connected network that is a shared responsibility between the water utility and building owner to flush out contaminants (National Research Council ). The Safe Drinking Water Act regulatory authority extends from the source water and intake, in the water treatment plant, through the distribution system and to the service line or meter on a given property (US EPA ). After that point, ownership of and management of water quality and delivery become the responsibility of the property owner (National Research Council ). Therefore, most drinking water utilities and regulatory agencies only have responsibility for water quality as it is delivered to the property line (National Research Council ). In most cases, state drinking water regulatory, or primacy, agencies have no role in building water quality or plumbing, nor do drinking water utilities, with the exception of backflow prevention, cross connection control and the Lead and Copper Rule (LCR) (Triantafyllidou ). Due to this governance construct, utilities are expected to recommend and communicate the need to take protective action to customers (National Research Council ). The complex logistics and compliance with guidance associated with staging was a factor that extended the incident for weeks (Schade et al. ). However, staging distribution system and BWS flushing has the advantage of preventing entrainment of contaminated distribution system water into BWS. Another benefit of deliberate staged pressure zone flushing is that it prevents excessive water demand, low water pressure, and the draining of certain sections of the distribution system (AMWA ).

Flushing as a public health intervention
For this study, flushing is defined as running water through components to turn over water in BWS to remove a contamination and prevent exposure to contaminated drinking water. Flushing is a de facto public health intervention wherein individuals choose to take an action to prevent exposure and consequential health effects. Alternatives to flushing, such as boil water advisories, have disadvantages, including potential injury, economic disruption, energy consumption, and low levels of compliance (Raucher et

Development of flushing protocols
Expert elicitation was used to assess current and prior protocols and to generate a new guidance based on the deliberation and professional experience. This method is a structured consultation approach to systematically assess expert opinion for topics with uncertainty (Knol et al. More complex scenarios can be adapted by adding safety factors or precautions or the use of personal protective Goal of flushing The fresh water from the water supply is free of the contaminant Target concentration after flushing is of 1-log reduction; 90% reduction in water heater Tap flow 0.8 gpm (EPA mandated minimum flow for low-flow faucets)

Plumbing components
Internal plumbing pipe diameter is 1-inch id Service line diameter is 1-inch id and 150 ft long 80-gallon water which acts as a continuously stirred tank reactor No point of use or point of entry filters equipment to the guidance for a specific contaminant. For example, a water contamination incident with a volatile compound could create a health hazard for those engaged with the flushing protocol. The following flushing guidance was developed for a simple contaminant non-volatile, nonreactive, conservative contaminant in an SFR plumbing and is based on a review of protocols, the expert elicitation, and our best engineering judgment. As such, more research is needed to develop evidence-based guidance. The following is draft language of the step-by-step procedures for customers to use to flush their building plumbing applying the flushing times and strategies.

How to flush your plumbing system
For the cold-water system, the following step-by-step actions are needed. For the hot water system, the following step-by-step actions are needed.
1. Run the hot water tap closest to the water heater.
2. Open all hot water taps.
3. If a bathtub has a spout and shower head, direct flow through the shower head first.
4. Allow the water to run for at least 75 minutes and then turn off the faucets.
5. If applicable, direct shower head flow to the bathtub tap for 2 minutes.
For appliances, the following step-by-step actions are needed.
1. Run empty dishwasher and washing machine once on rinse cycle.
2. Replace all water filters (e.g., whole-house filter, refrigerator filter) and empty ice from ice maker bin; run ice maker and discard two additional batches of ice.

Comparison of flushing guidance readability
The average American reads at a 7th-8th grade level  (Table 3). To our knowledge, this is the first study to evaluate the readability of flushing guidance. Seven of the eight flushing protocols evaluated in this study had reading grade levels above the recommendation for public health communications (9.5-12), with the reading ease ranging between 41.2 and 54.5 (Table 3). Only the protocol used after the Glendive, MT, benzene contamination incident and the experts' workshop guidance met the criteria for public health communications readability. In general, this protocol had clear, short sentences and paragraphs and simpler language.
Similarly, the flushing protocol developed in the experts' workshop was written to ensure that the Flesch-Kincaid grade level and Flesch readability were within the ranges recommended for public health communications. As such, the protocol readability score is 65.5, and the grade level is 7.2.

CONCLUSION
To our knowledge, this is the first study to use expert elicitation to develop a building flushing protocol and to evaluate the readability of flushing protocols. The flushing protocol and the guidance language provided in this study are a starting point until other studies can be conducted to develop evidence. The protocol is based on the best current knowledge and can be used as a resource when water providers must respond to a contamination incident. As is, this guidance is appropriate for flushing when the contaminant acts as a non-reactive tracer and poses no known significant health risks to those conducting the flushing or in the building during flushing. Additional actions depend upon the incident category, the building type, the audience, the information needed to prompt action, and the actions that consumers should take. Significant research and assessment are required to refine the protocol and guidance and make them the evidence-based, tested materials that would best serve the water community. Particular attention should be given to complex scenarios ranging from volatile contaminants associated with health hazards to certain types of plumbing materials. Safety factors or precautions, such as personal protective equipment, can be added to the guidance for specific contaminant characteristics.