Winter is Coming – How Will Your Sprinkler System Survive?

According to the Farmers Almanac, this winter will be freezing, frigid and frosty with wide temperature swings reminiscent of a Polar Coaster. Here's how you can prepare your building's fire protection systems to cope with the cold.

Wet pipe systems as their name suggests are filled with water and we know that water will freeze when temperatures drop below 32°F (0°C). And when water freezes it expands and can cause cracks in the pipe or fitting in which it resides. If any part of your wet pipe system is exposed to freezing temperatures, the system should be equipped with a heat trace system which is one accepted method of freeze prevention. Heat tracing is simply an electrical conductor which produces a small amount of heat when electricity is passed through it. This heat is usually sufficient to prevent a pipe, fitting or sprinkler from freezing. It is important to have this system inspected to ensure that it is functioning, is not damaged, and pipe insulation is intact. Follow the manufacturer's instructions for inspecting this type of system. (NFPA 25: 5.2.7).

Another method of freeze protection is to add liquid anti-freeze to the piping system which is very similar to the anti-freeze that is in your cars radiator. Anti-freeze solutions should be tested to make sure that the mixture will not freeze at the lowest anticipated temperature. If the mixture is not correct, replacement may be necessary, be sure to use a listed anti-freeze solution. Your sprinkler contractor can complete this test very easily. (NFPA 25: 5.3.4)

Where heat tracing or anti-freeze is not practical, a dry pipe system is normally installed. As its name suggests, the piping in a dry pipe system is not filled with water but is pressurized with air or nitrogen gas. Unlike a wet pipe system where the pipe can be installed level, the piping in a dry pipe system must be pitched to drain automatically. This can result in trapped sections of pipe which must be drained manually. To drain a system manually, a drain connection called a drum drip or simply low point drain is installed. This type of drain assembly permits releasing accumulated water without releasing sufficient pressurized air to trip the dry pipe valve. Water that accumulates in the system (due to condensation or testing) should be removed before freezing temperatures set in. In Figure from NFPA 13 (below), close valve “A”, remove the 1” (25 mm) plug, open valve “B: until all moisture has drained. Close Valve “B” and open valve “A”. Repeat this process until all moisture has been removed. (see NFPA 25, Chapter 13).


Where a dry pipe, pre-action or deluge system is installed, the system control valve must be installed in a heated enclosure. This enclosure must be heated since water is always present in the bottom of these valves and of course in the supply main. Now is a good time to test the heater and verify that adequate heat will be provided when the temperature outside drops. (see NFPA 25, Chapter 13).

Don't forget the outside of the building! This can include a number of things such as hydrants and water tanks! We very rarely think about hydrants until they are needed but now is a good time to flush that hydrant and get rid of any debris inside. More important, take note of how well (or how poorly) the hydrant drains. In cold climates if the hydrant has to be used and does not drain properly it will freeze. (NFPA 25: On the subject of hydrants, now is also a good time to flag that hydrant so it can be located when the snow piles up high. (NFPA 1: Don't forget some clear space around the hydrant after the snow starts falling. A good guide is 36 in. (900 mm) all around the hydrant and 60 in. (1500 mm) in front of the steamer connection. (NFPA 1:

If your system is supplied by a water tank, for most locations in the US, that tank must have a heating system. Is the heating system functioning correctly? (NFPA 25:9.2.3) The temperature of the water inside that tank is required to be maintained at 40°F (4°C). Low and high temperature alarms are required to be tested prior to the heating season. (NFPA 25:9.3.3 & 9.3.4). This is important because the tank is sized with a specific amount of water based on the calculated system flow and required discharge duration. If substantial ice builds up inside the tank, the ice will reduce the amount of available water from this required amount of water not to mention the possibility of damaging the tank itself.

Speaking of ice buildup. If your fire protection system is supplied by a pond or other natural or man-made source of water, does that water source freeze over? If it does, is there sufficient water left once frozen to meet the fire protection system demand? NFPA 24 is being revised to address such issues in Chapter 5 “Water Supplies”. The proposed revision includes a method for determining ice thickness to make sure that sufficient water is left over for fire protection purposes. It may be time for an evaluation to ensure that your natural source of water has sufficient capacity during the winter months.

Remember, according to NFPA statistics, 10% of sprinkler system failures are due to lack of maintenance and 7% of failures are due to damaged system components. With a little care these types of failures can be avoided when the temperature starts to drop!

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David Hague

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