Lawn Sprinklers/RPZ Backflow Preventer Permit

A building permit is required for the installation of a lawn sprinkler system.

The City of Naperville, in compliance with State of Illinois law, requires that all sprinkler systems include an RPZ (also called a backflow preventer). The RPZ is a check valve that prevents impurities, such as insecticides or animal wastes, from invading a home’s potable water system. This valve is crucial to maintaining the purity of a home’s drinking water and the safety of the community’s drinking water supply.

The City of Naperville has adopted a Cross-Connection Control Program. This program requires that all RPZs be tested when first installed and then annually thereafter. Upon installation, the owner must have the RPZ tested by a qualified, independent inspector and registered with Aqua Backflow ( The City then will verify the registration at the time of the final inspection.

If any portion of the sprinkler system is to be located within the public right-of-way/parkway, a Right-of-Way Encroachment License Agreement (PDF) must be completed and submitted along with the permit application.

Download the Lawn Sprinkler/RPZ Permit Application (PDF).

For details on the permitting process, including submittal, reviews, fees and issuance, visit the Building Permits page.