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Backflow Prevention

Des Moines Water Works (DMWW) is committed to providing safe drinking water to our customers. To do so, DMWW manages an active Cross-Connection Control program to meet state and local plumbing codes. This proactive approach is designed to prevent the possible contamination of the public water supply through backflow from customers’ facilities. DMWW works with specific backflow testers and testing companies that adhere to DMWW Rules and Regulations, so we can continue to provide you with quality water. DMWW has compiled a list of Backflow Tester List.
Our program brochure and rural brochure outlines how contamination can happen and how DMWW solves the problem.
If you have questions about cross-connection and backflow, please contact a licensed plumber or Des Moines Water Works at (515) 283-8775. To learn about specific backflow regulations, DMWW has provided a detailed overview of those regulations here.
What is cross-connection?
An actual or potential connection between the public drinking water supply and a customer’s plumbing system that makes it possible for used water, pollutants, or contaminants to enter the public drinking water supply.

How can a cross-connection be harmful?
lady illustration final-bwA pollutant or contaminant that enters the drinking water supply through a cross-connection can cause illness and spread of disease.

An example of a cross-connection that may be present at your home would be a hose-end sprayer used to apply lawn chemicals.
Problem:  If the pressure in the water main drops, the chemicals in the hose-end sprayer could be siphoned into the home and public drinking water supply.
Solution: This situation is easily remedied by installing a self-draining vacuum breaker onto the faucet.  Hose bib vacuum breakers are easy to install and readily available at your local hardware store.

What is backflow?
The undesirable reverse flow of used water contaminants or pollutants into the public drinking water supply as a result of a cross-connection.  Backflow can occur through backpressure or backsiphonage.

What is backpressure?
backpressure illustration finalBackflow caused by water pressure in a facility that is higher than the pressure of the public drinking water supply.  This may be caused by pumps, boilers, gravity or other sources of pressure.

Problem: The chemically treated boiler water could backflow through an open or defective valve into the building’s plumbing system due to the boiler system pressure being higher (80 lbs.) than the supply pressure (60 lbs.)
Solution: Installation of a backflow preventer on the water line at the point where it connects to the boiler.  This type of installation is referred to as “isolation.”

What is backsiphonage?
backsiphonage illustration finalThe reverse flow of used, contaminated or polluted water from a plumbing fixture or device into the public drinking water due to reduced pressure. This can be caused by nearby fire fighting, water main breaks or repairs.

Problem: If the public water supply pressure is reduced, chemicals in a mixing tank can be siphoned back through the water feed line, into the customer’s building and the public water main.
Solution: Installation of a backflow preventer on the water service line immediately after the water meter is required.  This prevents contaminated water from entering the drinking water supply through backflow.  This type of installation is referred to as “containment.”
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