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Main Drain Tests
Main drain tests have been required in previous editions of NFPA 25, Standard for Inspection Testing and Maintenance of Water Based Fire Protection Systems, for quite some time as a method to determine whether or not there is a reduction in flow of water to the fire protection system and to ensure that control valves are completely open.
Main drain test results are supposed to be compared to previous year’s results with the baseline test being the original acceptance test information noted on the Contractor’s Material Test Certificate for Above Ground Piping. A significant drop in pressure noted during a main drain test could indicate a serious problem such as a piping obstruction, or a partially closed or completely closed control valve.
When are main drain tests required? NFPA 25, 2002 Edition states annually at each riser (section 12.2.6), quarterly where water supply is through a back flow prevention device (section 12.2.6.1) and any time after a control valve has been closed and then reopened (section 12.3.3.4).
How is a main drain test performed? Main drain tests are very simple and can be conducted by facilities maintenance staff with minimal training. The steps for conducting a main drain test are as follows:
| 1. | Record static pressure indicated on the water supply gauge | |
| 2. | Close the alarm control valve on alarm valves | |
| 3. | Fully open the main drain valve | |
| 4. | After flow is stabilized, record the flowing pressure indicated on the water supply gauge | |
| 5. | Close main drain valve slowly |
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| 6. | Record the time taken for water supply pressure to return to original non-flowing pressure |
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| 7. | Open alarm control valve |
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| 8. | Compare results to previous tests and/or original acceptance test paperwork |
To download a short video demonstration of a main drain test, visit the U.S. Fire Administration’s website at http://www.usfa.dhs.gov/nfa/coffee-break. Look to the right for “Coffee Break Videos” and click on “Fire Sprinkler Main Drain Tests” or Click here to review the video.
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