Backflow Test Kits – Understanding How They Work

by Rick Marvel, Test Gauge – Elgin, IL

Within the backflow industry, a backflow test kit is the most important piece of equipment for any backflow tester.  While all backflow testers have this equipment, not all understand how a backflow test kit works, the standards the backflow test kit manufacturers must follow and how important accuracy checks truly are.

First and foremost, if a backflow tester does not understand the equipment they are using, it can lead to complications out in the field.  When using a backflow test kit, imagine it as a check valve on a backflow assembly.  A check valve on a backflow assembly consists of a piston (also known as a poppet), a rubber disc and a spring.  A backflow test kit has these same components on the inside.  The diaphragm assembly is the same as the poppet within the check valve; and the rubber diaphragm and spring does the same as the rubber disc and spring with in a backflow assembly check valve.  As water flows through the backflow test kit, the spring and diaphragm assembly push against the water acting as that of a check valve.  The only difference is the backflow test kit is then taking that pressure and converting it into a reading on your test kit.

Now being that the backflow assembly test kit is acting as that of a check valve assembly, you have to remember that it is also subjected to the same conditions as the backflow assembly.  Rusty water, debris and poor water conditions can lead to the possibility of periodically repairing your backflow test kit just like the check valve on a backflow assembly.

A backflow assembly must follow certain standards before going to market, as well as a backflow test kit.  Manufacturers of backflow test kits have two different standards that they must follow before bringing a product to market.  The first standard is the ASSE 1064 “Backflow Prevention Assembly Field Test Kits” and second, the University of Southern California’s “Manual of Cross-Connection Control” 10th Edition.

Both standards are very similar; however, there are some minor differences between the two.  For example, while USC 10th Edition requires a pressure holding of 175 PSI, the ASSE 1064 standard has a pressure holding requirement of 200 PSI.  There are also similarities between the two as well.  For example, both standards require an accuracy check on your backflow test kit at least once every 12 months.  They also require the test kit accuracy to be compared to equipment that is traceable to N.I.S.T. standards.

While both standards require an accuracy check of at least once every 12 months, this does not mean that the backflow test kit is required to be taken apart or repaired every 12 months.  Some general knowledge that you may need to know about Test Kit Accuracy and Test Kit Calibration are designated pressure points that the backflow test kit is checked at.  ASSE 1064 Standard requires the pressure points to be at 14.0, 7.0, 5.0, 2.0 and 1.0, to be performed in  descending order while USC 10th Edition requires designated pressure points to be at 12.0, 8.0, 5.0, 2.0 and 1.0, also to be performed in descending order.  You will need to know which test kit standard is required based on your individual state requirements.

Some helpful hints for keeping your backflow test kit in optimal performance are blowing out all test cocks prior to connecting your test kit to the backflow assembly, slowly open the test cocks while your test kit is connected so as to not shock your equipment and throw it out of calibration, drain your test kit after each use and the most important tip is protect your equipment from freezing.  The best way to protect your equipment from freezing is to store it with all the valves open and bring it out of the truck at night.  I have seen too many instances of equipment cracking, just because the backflow tester left the valves closed and out in a cold truck.

In closing, while it’s not necessary to know about each standard, it is necessary to know that the calibration company that you are using is following these standards that are set forth.  Using a company that does not have equipment that is at least .25% accurate and is not traceable to N.I.S.T. is the same as a company not using a licensed backflow tester to complete their backflow test.  To find a list of calibration companies that follow these standards, contact the backflow test kit manufacturer for a list of authorized calibration labs.

For any questions about test kit calibrations please feel free to contact me at (866) 836-8692.

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