A homeowner or business owner is responsible if their water system contaminates the public water system.
The water utility, in conjunction with Washington State Department of Health (WAC 246-290-490), requires customers within the City of Renton, that have the potential to back-flow water into the public water system, to install backflow prevention devices. The most common concerns are commercial and multi-family services, lawn irrigation, and fire suppression systems. The protection required for these systems is a 
Double Check Valve or a Reduced Pressure Backflow Assembly, depending on the level of potential hazard.
The required protection assemblies must be listed on the Washington State Department of Health list of approved devices. Because these are mechanical devices, and are not immune to failure, they must be tested regularly. A certified Backflow Assembly Tester will test upon installation and annually thereafter. Installation and annual test results are required to be sent to the City of Renton.
The purpose is to protect the public water supply by preventing contaminants from entering the public water system.
The most common examples of cross-connections that need to be protected from are:
- Residential lawn irrigation systems, boilers, and garden hoses (using a garden hose that connects to attachments make it the number-one source for cross connections).
- Commercial medical and dental facilities, veterinary clinics, landscape irrigation, boilers, fire service protection, film processors, and post-mix soda machines.
If an individual triggers the requirements for installation of a backflow assembly or are considering installing an irrigation system or fire sprinkler system, please contact the Cross Connection Control Specialist for installation procedure and policies.
iBackflow (Online Backflow Test Reports)