Backflow Testing

What is Backflow Testing for a Lawn Sprinkler Irrigation System?

A Backflow test is a required test that must be performed on an RPZ device (Reduced Pressure Zone) of your Lawn Sprinkler Irrigation System to protect your potable (drinking) water and the public water supply system from contamination or pollutants by preventing Backflow through the client’s water service connection and into the public water supply system. 

Why do I need Backflow Testing?

A Backflow test for your sprinkler irrigation system is required by the Lake County Public works Water Use Ordinance which can be accessed below under “Links”.

An RPZ unit is required by The Illinois Plumbing Code. You can find the Code below under “Links” with correlating government websites that list these codes.

A backflow test is the responsibility of each customer to protect the Water Facilities from contamination and to prevent backflow into the Water Facilities by ensuring that all cross-connections are removed or that approved cross-connection control devices are installed for control of backflow and back-siphonage.

Common contaminants can enter your drinking water system without proper protection. Things or events such as fertilizer and pesticides sprayed on the lawn or plants, neighborhood hydrant flushing, or city water main breaks can all create contamination. Without the protection of an RPZ on your lawn sprinkler, you could be risking contamination to your tap drinking water or to a neighbor’s tap drinking water.

If an event such as a drop in pressure of the city water, home, or building water happens, instead of backflow into your water supply occurring, the RPZ valve will open and allow the potentially contaminated water to dump out on to the ground below it.   

When do I need to get a Backflow test?

A lawn sprinkler backflow test is required at the time of installation, as well as yearly following your spring startup. If you would like to get on our schedule for an RPZ Test after your lawn sprinkler system has been started for the year, please let our technician know at the time of your startup. If you forget while our technician is there for your startup, just give our office a call, and let us know you would like to schedule an RPZ Test. Either way, the RPZ test and certification will occur between 1-4 weeks following your lawn sprinkler startup.

How do I book an appointment?

  1. Fill out a contact form on our website, send us an email, or give our office a call stating you need an RPZ Test. 
  2. You will be asked for the following information:
    • Has your sprinkler system been turned on for the year?
    • Name, Address, and best phone number/email to reach you.
    • Is your RPZ unit located INSIDE or OUTSIDE (*outside is most common)
  3. You will be put on the scheduling calendar, and within a few days be informed of your testing date.
  4. Your RPZ will be tested, certified (Pass or Fail), and the results will be filed with the appropriate village or municipality where you reside.

***If your RPZ is outside, you do not need to be home for this test! (Most common)

If your RPZ is inside, someone will need to be able to give the tester access to the location of the RPZ – the process typically takes less than 30 minutes from start to finish***

How do I know if my RPZ has been tested?

You will know your RPZ test has been completed by going to the RPZ unit, and viewing the tag hanging from the RPZ unit itself. The tag will include the report and testing date as well as the PASS or FAIL stamp.

IF your RPZ unit fails the test, that indicates something needs to be repaired or replaced within the RPZ. 

The technician testing the RPZ unit, alerts the staff at Auto-Rain if a unit fails. We will then reach out to you directly to coordinate repair or replacement of the RPZ unit. 

Upon completion of repairs, your RPZ unit will then require re-testing to achieve a status of PASS. The passed RPZ test certificate will then be filed with your local village or municipality and you are in the clear to use and operate your lawn sprinklers for the remainder of the season!

The RPZ Test/Certify/File must happen every year after the opening of your sprinkler system! The charge is $90 plus any additional filing fees added by your village of municipality. An RPZ Test service includes: testing of the RPZ unit, Certification of the RPZ Unit, and Filing of reports to your local Village or Municipality. 

Please Note: This is a separate charge and service from your Spring Startup. 

All RPZ tests are conducted by a CCCDI “Cross Connection Control Device Inspector” which is required by state and local laws and ordinances.



Lawn irrigation sprinklers addressed on (Pages 17-22)—-Water-Use-Ordinance-PDF?bidId=


d) Lawn Sprinklers. Any lawn sprinkler system connected to a potable water supply shall be equipped with an RPZ. The RPZ may be located outside provided that it is protected from freezing or is removed at the end of the season, and it complies with Section 890.1130(g)(1).

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The Illinois Plumbing Code, 77 Ill. Adm. Code 890.1140(d) specifically requires that a reduced pressure principle backflow preventer assembly (RPZ) be installed on all lawn sprinkler systems to protect the potable water supply. This is a retroactive requirement due to health hazard concerns, as there have been recent documented cases of nematodes (which frequently thrive in lawn sprinkler systems) being drawn into home and neighboring plumbing. Thus, the possibility of nematode contamination, entry of fecal coliform or other microbiological contaminants due to pet or animal waste deposited on or near sprinkler heads, and possible chemigation practices (application of pesticides, weed killers, or fertilizers in proximity to or through lawn sprinkler systems), make this connection to the potable water supply system a high hazard.

Both Agency regulations, 35 Ill. Adm. Code 653.802(e)(1). and the Plumbing Code, 77 Ill. Adm. Code 890.1130, require testing of the backflow assembly at the time of installation and at least annually thereafter. RPZs cannot be installed in a pit, as they are subject to flooding. If left connected to the system through winter months, the assembly must be protected against freezing. A HotBox or HydroCowl decorative rock can be used when aesthetics are important.

Many lawn sprinkler owners remove the assembly in the fall when the system is blown out to prepare it for winter. The assembly is stored in a heated basement or garage. When the system is serviced and put back into use in the spring, the RPZ assembly is installed, tested and ready for another summer season. The recent Lawn Sprinkler Contractor Registration program does not impact the need to include lawn sprinkler systems in the water utility cross-connection program inventory of cross-connections. This registration program does not include a test of competency, nor does it allow the registered party to make determinations in conflict with Illinois EPA or Illinois Department of Public Health requirements. Water purveyors should continue to include lawn sprinkler systems as a potential hazard to the quality of drinking water in the public water distribution system, and should continue to require that annual testing be performed each spring, with a copy of the test results placed on file with the water company.

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