By Jim McHugh
From the April 2021 Issue
In freezing weather, dry and pre-action fire sprinkler systems have a significant Achilles heel if they are improperly maintained—the auxiliary drains. Auxiliary drains, also referred to as low-point drains or drum drips, are required on dry or pre-action fire sprinkler systems to collect condensation that forms in the pipes.
When improperly maintained, auxiliary drains can break and subsequently cause major flooding in a facility. The cost to repair and reset the fire sprinkler system itself is negligible compared to the cost of water damage mitigation, potential lost inventory, occupant interruption and discomfort, increased liability, and increased insurance premiums.
Luckily, planning and executing proper maintenance and using available equipment and solutions can help facility management prevent flooding caused by frozen auxiliary drains.
How Auxiliary Drains Freeze And Break
Auxiliary drains collect condensation that naturally forms in dry and pre-action fire sprinkler systems. This water accumulates in the valve until it is serviced and emptied. Code requires that auxiliary drains be serviced after the system operates, prior to freezing temperatures, and otherwise as needed. Every system is different, so the service interval, especially of the “as needed” category, will vary by system. However, even two ounces of collected water, if left unattended, has the potential to break a system.
When temperatures drop below freezing, the water in the unit freezes and expands. When temperatures rise slightly above freezing, the ice partially thaws, leaving a cap of ice above the water. When temperatures drop below freezing again, the newly frozen water has no room to expand due to the ice cap. So, the pressure of the new ice forming breaks the auxiliary drain.
A broken drain compromises system pressure and triggers the system to pump out water. Each minute, tens of gallons can gush out of the broken drain until the water is shut off.
Service Drains To Prevent Freezing
The simplest way to prevent auxiliary drains from freezing is to ensure they are serviced before freezing temperatures arrive. The process itself is simple enough. First, close the top valve to maintain system pressure. Second, remove the drain plug at the bottom of the drain. Third, open the drain valve to empty the water from the unit. When all the water is out, reverse the process to safely return the drain to its collection mode.
Performing the process incorrectly compromises system pressure and causes the system to trip. Fortunately, some drains on the market come with instructions printed on the label. Others even come with a plate that prevents both valves from opening at once, which makes it impossible to compromise system pressure. These can be useful options for facility management teams that want their in-house personnel to perform auxiliary drain maintenance.
Whether by in-house personnel or a fire protection contractor, auxiliary drains should always be emptied before temperatures dip below freezing.
One Missed Drain Can Compromise The System
Even with intentional maintenance before freezing temperatures, simple human error can compromise the system. A system may have multiple auxiliary drains on it, and all it takes is one missed drain to trip the system and cause a flood. NFPA 13 code requires a sign at the dry valve listing the locations of all auxiliary drains on the system, but this is often overlooked. Even with a list of locations, maintenance staff may still miss a drain.
Water detector alarms provide a solution to this. These alarms attach to the bottom of an auxiliary drain and detect for the presence of water. When the drain contains enough water to need servicing, it sends out a notification. This helps maintenance personnel find the drains that need servicing, so it is less likely for one to be overlooked. However, this still relies on a prompt response. If the alert is not tended to fast enough, the drain could still freeze and break.
Protect Drains In Extreme Weather
In early 2021, unusually cold weather that hit the southwestern United States proved that freezing temperatures cannot always be anticipated. Extreme weather may catch maintenance personnel off guard. If a drain is already broken, focus should shift to mitigating the amount of damage that occurs. If maintenance personnel check the drains during freezing temperatures, they may be able to find the frozen drain before it starts leaking and close the top valve to prevent the flood.
A device (shown here) also exists that can be installed above an auxiliary drain to stop flooding from a broken drain. It detects the sudden flow of water from a broken drain and closes itself to severely limit the amount of water able to flood the facility. The auxiliary drain and fire sprinkler system will still need repair and service, but any water damage to the facility will be severely limited.
The required attention and maintenance might seem overwhelming, but what if the auxiliary drain could protect itself in freezing temperatures? Heated cabinets are available that sense when the outdoor temperature is below freezing and engage a heater to protect the auxiliary drain from freezing. This allows for infrequent maintenance with no consequences. Plus, for climates where freezing temperatures are few and far between, the auxiliary drain is automatically protected without additional action from maintenance staff.
Some versions of heated cabinets also contain options for fully automatic draining. This takes away the worry of auxiliary drains. Not only will the drain stay protected from freezing temperatures, but it will also take care of draining itself when needed.
Take Auxiliary Drains Seriously
Auxiliary drains may seem like an insignificant piece of a fire sprinkler system, but if ignored, these have the potential to cause some serious damage to a facility. No matter what level of protection a building owner wants to install for auxiliary drains, there are options. From a device to limit the damage, to a cabinet that takes care of it all, consider how you can improve auxiliary drain maintenance and lower the risk of major flooding during the next bout of freezing weather.
McHugh and his family have been involved in the fire sprinkler industry since the founding of AGF Manufacturing, Inc., and the introduction of the AGF TESTANDRAIN® valve. Currently serving as President of AGF, he is responsible for the development, introduction, and manufacture of specialized valves and products designed for the fire sprinkler industry. He is a member of NFSA, NFPA, SFPE, ASPE, and AFSA.
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