Water Safety and Backflow Prevention

Protecting drinking water, conserving water resources, and providing resilience to all buildings

[ Page 2 of 5 ]

Sponsored by WATTS Water Technologies, Inc.

By Celeste Allen Novak, FAIA, LEED AP

LACK OF HYDRAULIC CONTAINMENT IN HAZARDOUS AREAS

Often failures in cross-connection systems can be caused by maintenance failures combined with the inadequate design of the plumbing systems for a hazardous area. According to one case study highlighted in the EPA Cross Connection Control Manual, maintenance failures combined with the inadequate design of the plumbing systems led to serious illnesses and deaths in a health-care facility.³

Ethylene glycol entered the dialysis equipment through a series of events triggered by a valve being left slightly open. This valve permitted water to flow into a holding tank used to replenish a mix of glycol and water to the air-conditioning system. Glycol is customarily used in air-conditioning water to keep it from freezing in cold weather. With the valve partially open, water continually flowed slowly into the holding tank until the pressure in the holding tank equaled the pressure in the water supply.

Investigators theorized that someone in the medical center flushed a toilet or turned on a faucet, which dropped the pressure in the water pipes, allowing the glycol-water mixture to drain from the holding tank and into the medical center’s water pipes. Consequently, the contaminated water entered the dialysis filtration system used to purify water for the dialysis machines. This filtration system takes out trace chemicals, such as those used at the city water treatment plant; however, the system could not handle the sudden heavy load of chemicals.

Patients were sickened and all were moved promptly to intensive care, where their blood samples revealed a buildup of acid. Although ultimately the courts found that the company was not liable for the death of two patients, the emotional cost and actual costs of this tragic disaster may have been prevented.

Tests of the water supply to the dialysis filtration system confirmed the presence of “an undesirable chemical in the water purification system.” Investigators located the defective valve that had permitted the glycol-water mix to drain from the air-conditioning holding tank into the medical center’s potable supply lines and then into the dialysis filtration system equipment. If the water supply to the glycol tank had been air-gapped or protected with a reduced pressure principle backflow preventer, the dialysis machines would not have been contaminated.

This incident highlights the need for hydraulic containment of hazardous areas in hospitals and medical centers. Mortuary rooms, autopsy rooms, laundry rooms, boiler rooms, air-conditioning units, and pharmacy rooms should all be isolated and contained with the use of backflow preventers on their potable supply lines.

Early design coordination between the architect, mechanical, and plumbing engineer will determine the necessity for isolating hazardous chemicals from contaminating a drinking water supply.

Integrated Design Management: Schematic Design

Twenty-first century buildings are “machines for living, working, and playing,” to paraphrase 20^th century architect Le Corbusier. As technology advances, building design management requires a sophisticated, complex team of professionals. Integrated design management teams include all members of the design team who provide a holistic approach to the challenges and opportunities that can occur from schematic design through the commissioning of a project. Teams that include the architect and engineers from the beginning of a project have the advantages of predicting any scheduling issues, from the delivery of components to regulatory delays.

The key elements to a cross-connection control program include the isolation of the domestic water supply and containment at the meter, resulting in total backflow protection through the use of backflow preventers. Isolation requires an analysis of any cross-connections in the project. The appropriate backflow prevention devices will be selected to isolate any hazard to that location and protect the owner’s potable water system from contamination.

Total backflow protection is governed and regulated by The Uniform Plumbing Code (UPC) in Chapter 6, Section 608: Isolation Protection & Containment.⁴ “Containment” is the containment of a property’s private water system from the city’s drinking water supply system. This is done downstream of a property’s water service connection (the water meter) and achieved by installing a backflow prevention device immediately after the water meter. The water distribution system, fixtures, and piping are also governed by this code. Distribution flow rates and flow pressures are identified in Table 604.3 of the plumbing code.

In schematic design, the regulatory overview of cross-connection controls will impact the size of mechanical rooms, ceiling plenums, and fire safety controls. Regulatory overview will impact scheduling. In the schematic design phase, a review of the key cross-connection controls and permitting requirements will assist with project design and planning.

Agency Approvals and Code Compliance

There is a long history to the regulatory overview of plumbing systems. Although the complex overlapping of authorities may seem confusing, they provide a public water safety net. Design professionals need to understand who the Authority Having Jurisdiction (AHJ) is, as well as regulatory industry standards, particularly critical when the project includes fire safety systems. Typically, the property line divides whether the system is governed by the plumbing code or the AHJ. The American Water Works Association provides a list of some of the responsible water safety enforcement authorities.⁵

Local plumbing and building officials enforce all provisions of the applicable plumbing and building codes relative to installation, repair, maintenance, and operation of all plumbing system devices.
Fire marshals are responsible for regulating fire protection systems (e.g., fire sprinkler systems) downstream of the potable water system supply connection entering the premises.
Safety inspectors (Occupational Safety and Health Administration [OSHA]; Workers’ Compensation Board [WCB] [Canada]; Mine Safety and Health Administrators [MSHA]) are responsible for inspecting potable water systems (plumbing) for worker safety.
Health officials are responsible for inspecting restaurants and other food preparation facilities (e.g., dairies), health-care facilities (e.g., nursing homes), etc.
Agricultural inspectors are responsible for the safe handling of chemicals (e.g., pesticides) used in growing and processing agricultural products. Water purveyors deliver drinking water to customers and will have jurisdiction over water supply systems. These entities are public utility water companies, county water districts, or municipalities that deliver drinking water to customers. The mechanical or plumbing engineer with local knowledge may be the first source for information as to code compliance for cross-connection controls. As a condition of being connected to the public water supply, the municipality or water purveyor will typically have jurisdiction over the containment backflow. A device might be allowed in one county but not the adjacent county, and in one state but not the other. These professionals will also have relationships with the local plumbing inspectors, avoiding misinformation and delays. The basic guiding principles for specifying cross-connection controls depend on the answers to the following questions.
Is the building area or equipment device considered a health hazard or a non-health hazard?
Is a testable or non-testable device required?
Will a pressure vacuum breaker versus a reduced pressure principle device be required for irrigation?
Is a “not lead-free” system allowed as with certain non-potable applications, such as irrigation or hydronic heating systems?

The answers to these questions will save money, time, and potentially avoid an inspection failure or the installation of a more expensive device when a more economical one would have satisfied the requirements.

The major standards in the industry are: The International Association of Plumbing and Mechanical Officials (IAPMO), the American Society of Sanitary Engineers (ASSE), the University of California Foundation for Cross-Connection Control and Hydraulic Research (USC-FCCCHR), the American Water Works Association (AWWA), and NSF International (formerly the National Sanitation Foundation). These organizations provide information, education, product testing, product evaluations, and certifications.

Backflow preventer installation requires the services of a licensed professional engineer (PE) and licensed master plumber (LMP). A licensed professional will determine if a project requires a backflow preventer or multiple devices, or if the project qualifies for an exemption. The law also typically requires annual testing and inspection by a certified tester, and a report submitted to the Department of Environmental Protection (DEP) or AHJ. Failure to comply can lead to penalties and termination of water service. Backflow preventer devices are made up of moving parts, seals, and springs and are subject to corrosive substances, wear, and fatigue. Selecting the correct device and understanding annual testing and maintenance are just the beginning of a system that will require meeting the regulatory requirement that protects public health, safety, and welfare.

Construction Documents and Specifications

Engineers recognize that there are several major considerations for specifying backflow, including the importance of code compliance and agency approvals. The main elements include flow performance, calculated building flow, and hazard conditions. The resiliency of these devices for future maintenance, repair, and replacements depends on their serviceability, valve size, weight, installation options, shutoff options, and testing ability.

The problems that occur due to inadequate accessibility, lack of shutoffs, and improper orientations can lead to flooding, avoidable expenses for repair, and premature replacement.

Some typical problems include the following examples:

Inaccessibility due to the improper placement in a nest of plumbing pipes.
Improper orientation into a plumbing system for which it is not rated.
The removal of factory-approved parts in testable backflow assemblies that negate testing abilities.
Incorrectly placed fittings on vacuum breakers on faucets that defeat pressurization controls.

Mechanical rooms must be designed for the proper installation, accessibility, and maintenance of all cross-connection controls. Many of these controls are designed to discharge water during testing and upon failure and should be located where there is an appropriate area for drainage.

The valve shown in blue is not accessible for testing, a code requirement. This installation will require additional maintenance charges for years to come.

Architect Robert Allen, AIA, associate principal at Bowie Gridley Architects, describes his approach to cross-connection controls as a design challenge. He reports that he is always aware of the necessity for access panels, appropriate fire safety installations, and the visual effect and impact of fixtures in ceilings and walls of these devices. As someone who is engaged with the adaptive reuse of historic buildings as well as historic preservation, he is aware of the importance of analyzing the existing mechanical infrastructure of these systems. For example, fire safety controls can be an important part of the project and have numerous design implications. His decisions require him to understand what is specified in each project manual provided by the engineers.