The Safe Drinking Water Act (SDWA) was enacted in 1974 to protect public health by regulating the nation’s public drinking water systems. Under the SDWA, the U.S. Environmental Protection Agency (EPA), in partnership with state primacy agencies, establishes and enforces drinking water quality standards to ensure safe water is delivered to the public.
Millions of Americans receive high-quality drinking water every day. However, the safety of water at the tap inside buildings should not be taken for granted.
While public water systems are responsible for delivering water that meets federal standards at the service connection, the quality of water consumed inside homes, businesses, schools, hospitals, and public buildings can be compromised by the internal plumbing system itself.
Where Responsibility Ends — and Where Risk Begins
State drinking water programs and the EPA require public water systems to comply with the National Primary Drinking Water Regulations (NPDWR). These regulations establish enforceable Maximum Contaminant Levels (MCLs) for drinking water.
By definition, an MCL is the maximum allowable level of a contaminant in water delivered to any user of a public water system. Notably, the law references delivery, not necessarily consumption at the tap.
Public water systems are required to meet NPDWR standards up to the service connection. But what happens after the water enters the building?
Premise Plumbing: The Hidden Vulnerability
Water consumed inside a building may be exposed to contamination caused by unprotected plumbing cross-connections within the internal distribution system. These conditions represent a loss of physical integrity and allow contaminants to enter potable water through backpressure or backsiphonage.
Federal research has consistently shown that uncontrolled cross-connections present a significant public health risk, allowing chemical and biological contaminants to enter drinking water systems.
The EPA’s Cross-Connection Control Manual states plainly:
“Plumbing cross-connections, which are defined as actual or potential connections between a potable and non-potable water supply, constitute a serious public health hazard.”
In short: water that reaches the last free-flowing tap is not automatically safe to drink.
The Regulatory Gap in Premise Plumbing
The NPDWR and many state drinking water programs do not directly regulate internal plumbing systems within buildings. These systems are often considered the responsibility of:
- Building owners
- Plumbing code officials
- Local authorities having jurisdiction (AHJs)
While public water systems may acknowledge the risks associated with premise plumbing, responsibility for controlling cross-connections is frequently deferred, creating gaps in public health protection.
Plumbing Codes Provide the Framework
Both the Uniform Plumbing Code (UPC) and International Plumbing Code (IPC) establish clear requirements for protecting potable water within buildings.
Key provisions include:
- Potable water must be supplied to all plumbing fixtures
- Plumbing systems must be designed, installed, and maintained to prevent contamination from non-potable sources
- Cross-connections must be eliminated or properly protected
When plumbing codes are followed and enforced, water consumed within a building does not pose a public health risk.
Unfortunately, inconsistent enforcement of plumbing codes and cross-connection control programs remains a nationwide problem.
When Public Water Systems Step In
When public water systems determine that plumbing code enforcement is insufficient to protect the distribution system, many require the installation of a backflow prevention assembly at the service connection.
In some states, this requirement is mandated by regulations. In others, it is implemented as a policy condition for water service.
However, it is critical to understand what this device does and what it does not do.
Service Line Protection Is Not Cross-Connection Control
A backflow prevention assembly installed at the service line protects the public water system, not the internal plumbing system. It should be viewed as a service line protection device, not a comprehensive cross-connection control measure.
If the service line assembly were considered true cross-connection control:
- Water downstream would be considered non-potable
- Plumbing code requirements would be violated
- Fixtures could not legally be supplied with potable water
This creates a fundamental conflict between drinking water regulations and plumbing codes.
Why Service Line Protection Alone Is Insufficient
Installing a backflow prevention assembly at the service line does not:
- Eliminate internal cross-connections
- Protect occupants from internal contamination
- Ensure water at the tap is safe to drink
Unprotected cross-connections inside the building can still contaminate water even if the public system is fully protected.
The Correct Approach: Control Cross-Connections at the Source
True cross-connection control occurs where the hazard exists — inside the building. If a facility complies with plumbing code requirements for cross-connection control, both the public water system and building occupants are protected.
In this scenario:
- Service line backflow protection may be unnecessary (unless mandated)
- Internal potable water quality is preserved
- Public health risks are minimized
Service line protection can still be used as a supplemental safeguard, such as installing a double check valve assembly or residential dual check valve to protect the public system from hydraulic backflow.
Verifying Plumbing Code Compliance
A critical question remains: How does a public water system know a facility complies with the plumbing code?
The EPA recommends that public water systems require property owners to provide documented proof of compliance with applicable plumbing codes related to cross-connection control.
Responsibility is shared:
- Building owners must maintain compliant systems
- Plumbing officials must enforce the code
- Public water systems must notify and educate customers
Public water systems should clearly inform customers that:
- Service line backflow assemblies protect the public system, not occupants
- Internal plumbing hazards may still exist
- Plumbing code compliance is the owner’s responsibility
Additionally, risks associated with service line backflow assembles — such as thermal expansion, pressure loss, flooding, vandalism, and security — must be communicated.
A Path Forward in 2026
To protect consumers and restore confidence in drinking water safety:
- State cross-connection regulations should be updated
- Comprehensive cross-connection control programs must be funded and staffed
- Plumbing code enforcement must be consistent
- Consumers must be educated about water safety at the tap
Some jurisdictions may require a certificate of plumbing compliance to be posted within buildings, confirming that internal systems meet cross-connection control requirements.
So, Is Tap Water Safe to Drink?
It depends.
Tap water is safe only when cross-connections are properly controlled where they exist, plumbing codes are enforced, and public water systems and the plumbing industry clearly understand and communicate their respective responsibilities.
Protecting drinking water is a shared responsibility and public health depends on getting it right.
James Holeva
James Holeva has over forty years of experience in the environmental management field. He retired from the Massachusetts Department of Environmental Protection in 2003. His experience includes, drafting drinking water regulations and policies, chairing a board of certification for drinking water operators, managing the day-to-day operations of a drinking water supply watershed system, managing a state regional drinking water regulatory program that included enforcing federal and state regulations, and managing the day-to-day operations of a public works department. In alliance with NEWWA he has conducted numerous cross-connection control trainings throughout the New England States, NY, NJ and PA. In addition to conducting cross-connection control training, he taught environmental science courses at the college level and developed training programs for the water works industry and others. He served as the treasurer of a national certification association and was instrumental in redefining the examination process for drinking water operators and developing a national backflow prevention tester examination. As a function of his consulting business, he provides technical support and consultation to the water works industry and others with respect to cross-connection control and on-line training. He holds a BS degree from the University of Massachusetts.
