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Irrigation FAQ

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  • Do I need to purchase a permit?

    Yes. Any time an irrigation system is installed, the owner must purchase a permit. The purpose of the permit is to protect the public health and the quality of our water by ensuring the proper installation of the irrigation system.

  • Where do I get a permit?

    Permits are available from the Development Services Office at the City Service Center at 55 E. Moore Street.

  • Do I need to call for an inspection?

    A final inspection will be required after construction. It is the owner’s responsibility to call the City at 509.527.4387 to request a final inspection. The backflow preventer and any other possible water quality issues are the focus of the final inspection.

  • How do I know my design will pass inspection?

    If you wish, you may submit plans or a sketch to the City or stop by to discuss your project before starting construction. This will reduce the risk of having to modify your system after construction to bring it up to code. If you have concerns, you may call the Water Division at 509.527.4380 and ask to speak to someone about backflow prevention requirements on irrigation systems.

  • Is a backflow preventer always required?

    Yes, a backflow preventer is required for all underground irrigation systems connected to the City water system. This includes irrigation systems that use an alternative source but have City water available as a backup, whether or not it is turned off. The type of backflow preventer appropriate for each system will be determined by the City. This brochure includes a decision chart that may help you to understand how your system design will influence backflow prevention requirements.

  • I know what backflow preventer I need, but how do I install it?

    There are different installation requirements for each type of backflow preventer. You will need to obtain a copy of the current installation standard from the City for the type of backflow preventer you are installing. Always feel free to call for clarification if you have questions.

  • Do I need to test my backflow preventer annually?

    The City determines what backflow preventer type is required based on the degree of hazard and City requirements. Atmospheric vacuum breakers (AVBs) that are listed by the State of Washington Approved Assemblies List are allowed under certain conditions and do not require annual testing.

  • The City came out and inspected my irrigation system. Do I still need to have someone test the backflow preventer(s)?

     Yes, unless your backflow preventers are atmospheric vacuum breakers (AVBs). The City inspection is only to identify the backflow preventer(s) and verify the correct backflow preventer type has been used and installed correctly. A backflow assembly test confirms the backflow assembly is functioning properly, and must be conducted by a certified backflow assembly tester who is registered with the City of Walla Walla.

  • How much does a backflow assembly test cost, who does it, and how do I know when I need to have it done?

    Costs vary considerably, so you will need to call around to get the price and service you want. The City provides a list of backflow assembly testers that are certified by the State and registered with the City to test backflow assemblies. Once a year you will receive a letter by mail notifying you that the test is due. A list of backflow assembly testers is included with the letter.

  • What if I don’t want to have a backflow assembly installed or tested?

    If you have an underground irrigation system, and do not have a backflow preventer installed, the City will give you a period of time to have the backflow preventer installed, inspected, and tested (if applicable). If you refuse to install or test a backflow preventer after notification by the City, the City may refuse to serve you with water until you meet the requirements.

  • What if I don’t get my backflow assembly tested by the due date?

    The City will send you a notice to test the assembly once a year. If you can’t test it for some reason, you may request a reasonable extension (typically 10-14 days). A second (final) notice will be sent out after the due date if no test report is received. If you fail to test by the due date on that final notice, and fail to make alternative arrangements with the City to have it tested, the City may refuse to serve you with water.

  • How do I determine the static pressure for my calculations?

    Pressure varies throughout the City from about 40 psi to 100 psi, so you should purchase a water pressure gauge or call the Water Division to have your pressure tested.

  • How do I determine maximum flow for my calculations?

    Flow rates change according to meter model, service line size and length, and pressure. Approximate maximum flow rates (for continuous flow) according to our meter manufacturer are as follows:

    • ¾-inch meter – 15 gallons per minute (gpm)
    • 1-inch meter – 25 gpm
    • 1½-inch meter – 50 gpm
    • 2-inch meter – 80 gpm