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Backflow testing for sprinkler systems in Wentzville, MO

Missouri · Last checked November 2026

Test every year

Wentzville requires every lawn irrigation system to have a backflow preventer tested each year by a Missouri-certified tester, with reports due by June 1. You can instead deactivate the system by removing the device and booking a city inspection before June 1.

Key facts

Deadline
Test report due June 1.
Tester
Missouri-certified backflow tester.
Fee
$12 early-bird filing fee before June 1.
Opt out
Remove the device and schedule a deactivation inspection before June 1.

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How it works

A lawn sprinkler system connects to drinking water, so it needs a backflow preventer to stop fertilizer and lawn water from being pulled back into the pipes. Most cities require that device to be tested by a certified tester, usually every spring, with the report filed by a set date. Miss it and you can face late fees or a water shutoff notice.

  1. Find the backflow device near where the sprinkler line leaves the house, often a valve assembly above ground.
  2. Check your city's deadline. Many fall between May 31 and June 15.
  3. Hire a tester certified in your state, or wait for the utility if it tests for you.
  4. Make sure the tester files the report with the city, and keep a copy.
  5. Not using the sprinklers? Ask about an inactive or deactivation certificate instead of a test.

What it costs

A residential backflow test usually costs about $50 to $150. Some cities add a small filing fee, around $12, and late fees can run $30 to about $80. Repairs to a failed device cost more.

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Sources

Last checked November 2026. Programs open, close and change funding every year. Confirm with the city before you hire anyone. Report a change.

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