| What is backflow? Backflow is the undesirable reversal of flow in a potable water distribution system through a cross-connection. A cross-connection is an actual or potential link connecting a source of pollution or contamination with a potable water supply. Backflow may allow liquids, gases, nonpotable water and other substances, from any source, to enter a public water system. How does backflow occur? Backflow may occur due to high pressure on the customer side, or low pressure in the water system. Backflow through a cross-connection can contaminate the potable water in a building, on a block, or throughout an entire water system. What is backflow prevention? Backflow prevention protects public water systems from contamination or damage through cross-connections located in customer facilities. Backflow prevention is typically achieved by placing a backflow prevention assembly between the customer and the public water system. This is called containment backflow prevention. What kind of backflow prevention is required at my home or business? Under the Missouri rule, three types of backflow prevention assemblies are permissible for containment: air gaps, reduced pressure principle assemblies and double check valve assemblies. The type of assembly you need depends on the type of hazard present. Generally, where you have a backflow hazard that may threaten public health you must have an air gap or a reduced pressure principle assembly. Where there is a lesser hazard that may damage the water system or degrade the aesthetic quality of the water, a double check valve assembly is required.Only approved backflow prevention assemblies may be used. If you can find the manufacturer and model number on your assembly you can check with your water supplier to find out if it is an approved assembly. Modifications to an assembly invalidate the approval. If your assembly looks like it has been changed, get in touch with your water supplier or a certified backflow prevention assembly tester to see if it is an approved assembly. Water suppliers may have more strict or specific requirements than the state rule. Contact your local water supplier to make sure you have the appropriate backflow prevention assembly to meet local requirements. Must I have my backflow prevention assembly inspected? Yes. To ensure the device is functioning properly, a certified tester must test it at least annually. For new facilities, the assembly must be tested when installed. If the tester finds the assembly is not working, you must arrange to have it repaired and tested again. It is your responsibility to pay for the test and repairs. The tester is required to provide a copy of the test report to you and the water supplier. To obtain a list of certified testers in your area, call your water supplier or the Missouri Department of Natural Resources. |
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| Backflow Prevention FAQ |
Source: Missouri Department of Natural Resources - http://www.dnr.mo.gov/pubs/pub2158.pdf