The buildings in your community that have water fire suppression systems are required to have backflow preventers. Those devices are required by the local plumbing or sanitation code in order to keep water from flowing backward and contaminating the drinking water. But unlike other plumbing systems, the fire suppression system is only operated when the annual flow test is conducted or when there is a fire. Since the water does not flow, except for once a year, there is one failure that is typical in almost all backflow preventers for water fire suppression systems. You will need to pay special attention to the second check valve in the backflow prevention device. Here is why failures occur and what you need to do to keep your community’s drinking water safe.

Backpressure backflow of water is possible whenever the downstream water pressure exceeds the supply pressure. Without the required backflow preventer in a water fire suppression system (e. g. fire sprinkler system), a backpressure backflow condition would cause a backflow of water, meaning a reversal of water flow in the system and contamination of the drinking water.

A backpressure backflow condition is due to an increase in downstream pressure that is higher than the supply pressure. This can happen at night when there is little demand for water as businesses, like restaurants, shut down for the night. It also happens when there is thermal expansion, such as when a building is cold and is then heated. Whatever the reason, a higher pressure on the downstream side exerts pressure on the last check valve (second check valve) in the backflow prevention device. That backpressure gets trapped behind the valve disc or downstream of that second check valve.

The actual seal of the check valve seat relies on the rubber disc in the valve, which when closed and operating correctly creates a seal to the valve seat. This seal effectively prevents water from flowing past it and back into the drinking water supply. While it is the best method for mechanically sealing and preventing water from moving past the second check valve and back into the drinking water supply, it is also doomed to failure over time due to the nature of the rubber material to deform and deteriorate, caused by the constant pressure exerted on it by the backpressure of the fire suppression system.

Potential backpressure backflow is created whenever the downstream pressure exceeds the supply pressure. This will start to increase once the annual backflow test is completed and the system is put back into commission. Although there are devices like expansion tanks and pressure-relief valves that are intended to reduce some of the excessive pressure, there will always be pressure on the downstream side and therefore pressure on the rubber disc on the second check valve. The pressure remains until the next annual main-drain test on the fire suppression system. That pressure is what causes the rubber disc to deform and deteriorate over time, which eventually allows the pressures to equalize before and after the check valve.

There are two drivers for performing annual testing of backflow prevention devices. NFPA 25, Standard for Inspection, Testing, and Maintenance of Water-Based Systems, requires a forward flow test to ensure adequate water supply for sprinklers and other system components for fire extinguishment. The second driver is your local plumbing code, which requires annual testing of backflow preventers to ensure they are doing their job of preventing reversed water flow into the drinking water. To perform the operational test to ensure that there is no reversed flow, you will need to take pressure gauge readings using the four test cocks on double check valve backflow prevention devices. Those readings provide indications of problematic components that need either cleaning or replacement.

While performing the annual test on a double check valve backflow prevention device, you can determine that the second check valve is experiencing a failure if the pressure gauge reading at test cock #3 (TC#3) and TC#4 is the same (see diagram). A failure means that the valve is fouled (debris preventing full closure) or the rubber disc has worn to the point that it does not seal and allows flow and equalization of the pressures upstream and downstream of the second check valve. When this happens, you must disassemble the valve and check for debris and examine the rubber disc. After you have removed debris, replaced or cleaned the rubber disc and valve seat (creating a tight seal), you can then perform another test. You will know that you have resolved the problem when the pressure gauge reading is higher at TC#4 than at TC#3 with the fire suppression system back in operational condition.

Your customers expect their fire system devices to be code compliant and to keep their community’s drinking water safe. Anticipating the need to clean debris and possibly replace the second check valve rubber disc will save you time and keep your customers satisfied and their systems reliably safe. Knowledgeable technicians make for satisfied customers.

Double Check Value Device Assembly

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Implementation Expected for NDAA Mandate for Extinguishers at Military Bases

Mark Conroy, Brooks Equipment; Dwayne Garriss, FEMA Consultant: Guy Jones, Amerex

National Defense Authorization Act (NDAA), for Fiscal Year 2022, requires fire extinguishers to be installed within military facilities in accordance with NFPA 1, Fire Code. The new law came about due to a deficiency in the building code for the Department of Defense (DoD), called the Uniform Facilities Criteria (UFC). The current UFC allows extinguishers to be removed if a building has a sprinkler system and a fire alarm. The 2022 NDAA requires portable fire extinguishers for DoD facilities. The Act was signed into law in December, 2021. Although the NDAA became law, implementation has been slow and the UFC has yet to be updated.

The Government Relations Committee (GRC) of the Fire Equipment Manufacturers Association (FEMA) has met recently, by phone, with the offices of congress and then went to Washington, DC, on July 12 and 13, 2022, to meet with congressional staffers. Those in-person meetings, arranged by Rasky Partners, included staff from Sen. Tillis (R-NC), Sen. Shelby (R-Ala), Rep. Adams (D-NC), Rep. Rogers (R-Ala), and Rep. Palmer (R-Ala). These senators and representatives are in full support of an equivalent level of safety for US military personnel with the civilian side (state fire codes). FEMA GRC will continue to push for implementation of the NDAA.

FEMA GRC Meets with USFA on Extinguisher Use

The FEMA GRC met by conference call on July 15, 2022, with Dr. Lori Moore-Merrell, US Fire Administrator and Tonya Hoover, Deputy US Fire Administrator. United States Fire Administration (USFA) is in the process of updating their method for collecting data on fires in the US. The purpose of the meeting was to ensure that data on fire extinguisher use is included in USFA data collection efforts. The Request for Proposals (RFP) will be later this year and the new system will be online by 2025. Unlike the old pen-and-paper system, data for the new system will be entered by smart phone. Also, USFA is looking to capture data on all fires, rather than just those with fire department responses. This new system is expected to capture data on fires, where extinguishers are used successfully but are often unreported.