Backflow Prevention: What it is, why it’s required, and how testing works

A practical overview for homeowners, property managers, and commercial properties.

Protecting the Public Water Supply

Backflow prevention is a crucial safeguard designed to protect drinking water from contamination. When conditions cause water to flow in the reverse direction, contaminants can enter the potable water system.

Because this risk affects both private properties and public infrastructure, local water authorities require backflow prevention devices and regular testing in many residential, commercial, and multi-family applications, including apartment communities, condominiums, and mixed-use residential properties.

Backflow occurs when water reverses direction within a plumbing system due to changes in pressure. These pressure changes can happen suddenly and are often outside the control of the property owner.

There are two primary conditions that cause backflow:

What causes backflow?

Backpressure

Backpressure occurs when downstream pressure becomes greater than the supply pressure. this can happen in systems such as irrigation pumps, boilers, or fire protection systems where pressure is introduced into the system.

Both conditions present a risk to the potable water supply if proper backflow protection is not installed and maintained.

Backsiphonage

Backsiphonage occurs when supply pressure drops creating a vacuum effect that pulls water backward through the system. Common causes include water main breaks, firefighting activity, or high system demand.

Why Backflow Testing is Required

Backflow testing requirements exist to protect public health and maintain the integrity of the potable water system. When backflow occurs, contaminants from private plumbing systems can enter the public water supply, creating a risk that extends beyond a single property.

For this reason, local water authorities require backflow prevention devices on certain plumbing systems and mandate regular testing to verify proper operation.

There requirements are typically enforced through local cross-connection control programs and apply to many residential, commercial, and multi-family properties. Testing intervals and device requirements are determined by the water authority based on the level of hazard associated with the property or system.

  • Protects the public drinking water supply

  • Reduces the risk of contamination events

  • Ensure compliance with the local and state regulations

  • Provides documented verification of system protection

Common Backflow Prevention Devices

  • A double check valve assembly is commonly used in low to medium hazard applications where the risk of contaminations is considered minimal. These devices are often installed on certain fire sprinkler systems or commercial water services that do not involve chemical additives.

    Double Check assemblies provide protection against both backpressure and backsiphonage but are not approved for high-hazard conditions.

  • A reduced pressure zone assembly is required for high-hazard applications where there is an increased rick of contamination entering the potable water supply. These devices are commonly installed on irrigation systems, commercial properties, and facilities that use chemicals or auxiliary water sources.

    RPZ assemblies provide the highest level of protection and are subject to strict installation and testing requirements established by the local water authority.

  • A pressure vacuum breaker is typically used on irrigation systems to protect against backsiphonage caused by a drop in supply pressure. These devices must be installed above ground and in accordance with specific clearance and height requirements.

    Pressure vacuum breakers are designed to prevent reverse flow but do not protect against backpressure.

  • The type of backflow prevention device required for a property is determined by the local water authority based on hazard classification, system design, and applicable codes. Property owners are responsible for ensuring that the correct device is installed, maintained, and tested as required.

    A certified backflow technician can help identify existing devices and confirm compliance with local requirements.

Request Backflow Testing

What is Backflow Testing?

Backflow testing is a standardized procedure performed by a certified technician to verify that a backflow prevention device is operating as intended. Testing ensures that internal components are functioning properly and that the device will prevent reverse flow under varying pressure conditions.

Testing is conducted using calibrated equipment and must be performed in accordance with procedures recognized by local water authorities.

During testing, the technician evaluates pressure differentials, valve operation, and internal seals to confirm that the device meets required performance standards. Test results are documented and submitted to the appropriate water authority to maintain compliance.

  • Verifies proper device operation

  • Identifies failing or worn components

  • Provides required compliance documentation

  • Helps prevent service interruptions or penalties

What Happens If a Device Fails Testing?

A failed backflow test indicates that the device is no longer providing the required level of protection. This does not necessarily mean contamination has occurred, but it does mean corrective action is required to restore compliance and protect the water supply.

Depending on the cause of failure, corrective action may include cleaning, repair, replacement of internal components, or full device replacement. All repairs must be completed by a qualified technician and retested to confirm proper operation.

  • Minor issues may be corrected through repair or cleaning

  • Worn or damaged components may require replacement

  • Severely compromised devices may need full replacement

  • Retesting is required after any repair or replacement

Local water authorities may issue compliance notices or enforcement actions if a failed device is not corrected within the required timeframe.

Who is Responsible for Backflow Compliance?

In most jurisdictions, responsibility for backflow prevention compliance rests with the property owner. This includes maintaining the backflow prevention device, ensuring required testing is completed, and submitting documentation to the appropriate water authority.

This responsibility applies to residential properties, commercial buildings, and multi-family properties, including apartment communities, condominiums, and mixed-use developments. Property managers often coordinate testing and documentation on behalf of owners but are not typically the legally responsible party.

  • Maintaining the installed backflow prevention device

  • Scheduling required testing at mandated intervals

  • Completing repairs or replacements when necessary

  • Ensuring test results are properly submitted

Staying current with backflow testing helps avoid compliance notices, penalties, and potential interruption of water service.

Needing Testing or Have Questions?

If you have received a notice from your water provider, manage a property, or are unsure whether your system requires backflow protection, assistance is available.

Backflow Boss provides backflow testing, diagnostics, and repair services for residential, commercial, and multi-family properties throughout Missouri and Kansas. All services are performed by certified technicians and include proper documentation and reporting.

Requests are reviews by a certified technician, and follow-up is provided as needed to confirm the next step.

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