Water Backflow

Notice of Testing Requirement for Customers

Protecting the public water supply from contamination.

Cross Connection contamination of the public water supply is the leading cause of waterborne disease in public water systems. It can occur when any fluid or gas that is contaminated is introduced into the public water supply. Anywhere in the public or customer water lines where this can occur is considered a “cross connection.” Hermiston Water Dept. is mandated by the State of Oregon Drinking Water Rules to eliminate or control all cross connections.

Cross connections can include garden hoses left submerged in buckets, hose-end chemical spray attachments, including pump type garden sprayers, lawn sprinkler systems, fire sprinkler systems, and auxiliary private water systems to name just a few. Cross Connections are controlled by the installation and annual testing of backflow prevention assemblies.

Backflow prevention assemblies are devices that can be installed in your water system to prevent water from flowing back into the public water supply. Backflow prevention assemblies are required by Oregon law to be tested at least annually by a State certified tester. If you know of backflow prevention assemblies at your property, be sure to have them tested.  For a list of Oregon Certified testers see the website: https://yourwater.oregon.gov/backflow.php

Backflow Prevention Frequently Asked Questions

Is backflow prevention required?

Yes, where a cross-connection and/or backflow can occur. The State of Oregon requires backflow prevention devices to be installed, then tested annually to protect the health & safety of the public water system. In order to meet state law, the City is required to moniter testing of the devices.  

What is a cross-connection?

A cross-connection is any temporary or permanent connection between a public water system or consumer's potable (i.e., drinking) water system and any source or system containing nonpotable water or other substances that are not safe to drink or may impact the taste or odor of water. Common cross connections include hot tubs, pools, sprinkler & irrigation systems & auxiliary water systems (wells).  

What is backflow?

Backflow is the undesirabble reversal of flow of nonpotable water or other substances through a cross-connection and into the piping of a public water system or consumer's potable water system. There are two types of backflow... backpressure backflow and backsiphonage.  

What is backpressure backflow?

Backpressure backflow is backflow caused by a downstream pressure that is greater than the upstream or supply pressure in a public water system or consumer's potable water system. Backpressure (i.e., downstream pressure that is greater then the potable water supply pressure) can result from an increase in downstream pressure, a reduction in the potable water supply pressure, or a combination of both. Increases in downstream pressure can be created by pumps, temperature increases in boilers, etc. Reductions in potable water supply pressure occur whenever the amount of water being used exceeds the amount of water being supplied, such as during water line flushing, fire fighting, or breaks in water mains.

What is backsiphonage?

Backsiphonage is backflow caused by a negative pressure (i.e., a vacuum ~ or partial vacuum) in a Public water system or consumer's potable water system. The effect is similar to drinking water through a straw. Backsiphonage can occur when there is a stoppage of water supply due to nearby fire fighting, a break in a water main, etc.

Who can test my backflow device?

An Oregon State Certified tester can test your device.

Can the Certified Tester repair or replace my device if it fails?

No, IF they are not also a licensed plumber. The State requires that a licensed plumber (or the owner) do the repair or replacement. Many licensed plumbers are also certified to perform the test. If your device fails the test, once it's repaired or replaced it must be tested to ensure it is working properly.  

How often does my device need to be tested?

Backflow assemblies must be tested at the time of installation, annually after installation, after repairs and after relocating.

Why do water suppliers need to control cross-connections and protect their public water systems against backflow?

Backflow into a public water system can pollute or contaminate the water in that system (i.e., backflow into a public water system can make the water in that system unusable or unsafe to drink), and each water supplier has a responsibility to provide water that is usable and safe to drink under all forseeable circumstances. Furthermore, consumers generally have absolute faith that water delivered to them through a public water system is always safe to drink. For these reasons, each water supplier must take reasonable precautions to protect its public water system against backflow.

What is a backflow preventer or device?

A backflow preventer is a means or mechanism to prevent backflow, basically keeping water from flowing backwards into the public water main. The basic means of preventing backflow is an air gap, which either eliminates a cross-connection or provides a barrier to backflow. The basic mechanism for preventing backflow is a mechanical backflow preventer, which provides a physical barrier to backflow. The principal types of mechanical backflow preventer are the reduced-pressure principle assembly, the pressure vacuum breaker assembly, and the double check valve assembly. A secondary type of mechanical backflow preventer is the residential dual check valve.

What is an air gap?

An air gap is a vertical, physical separation between the end of a water supply outlet and the flood-level rim of a receiving vessel. This separation must be at least twice the diameter of the water supply outlet and never less than one inch. An air gap is considered the maximum protection available against backpressure ro backsiphonage but is not always practical and can easily be bypassed.

Additional questions?

For questions not answered above regarding backflow, please contact the City of Hermiston Water Department at 541-567-5521.


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