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Use of Glycerine in Fire Sprinkler Systems

Fire sprinkler systems protect homes, offices and factories from fire danger. Sprinklers charged with water must themselves be protected against freezing in the wintertime. Traditional antifreeze can be toxic and will degrade certain types of fire suppression systems. A better choice is glycerine, which can be used in a sprinkler to protect the system against cold temperatures.

  1. Glycerine as an Antifreeze

    • Glycerine, also known as glycerin or glycerol, is a naturally occurring sugar alcohol. Glycerine lowers the freezing point of water by inhibiting ice crystal growth. Its low toxicity makes it a common choice for weatherproofing residential and commercial fire sprinkler systems. The National Fire Protection Association (NFPA) sets standards for sprinkler systems and requires that any system expected to be exposed to freezing temperatures must be protected by an antifreeze solution. NFPA code 13 requires any sprinkler system connected to a public water source must use a glycerine antifreeze solution rather than ethylene glycol to reduce the risk of poisonous chemicals returning to the water supply. In fire suppression systems containing chlorinated polyvinyl chloride (CPVC) pipes glycerine must be used as an antifreeze as ethylene glycol can corrode the plastic pipes and fittings.

    Concentration and Testing

    • Fire suppression systems use a closed loop to isolate freeze-proofed areas. A check valve keeps antifreeze from returning to the main sprinkler system. Glycerine offers highest antifreeze protection at a 70 percent concentration by weight. At this level, pipes are protected against freezing to minus 36 degrees Fahrenheit. Above this concentration glycerine will begin to freeze at higher temperatures: pure glycerine begins to solidify near 32 degrees F. Check with your local Fire Marshal to find the concentration required for your climate. Manufactures offer premixed glycerine solutions though you can blend your own mixture using food-grade glycerine and distilled water. Open the filling inlet to load the antifreeze into the sprinkler system. Use a laboratory grade hydrometer or a refractometer to test that the glycerine solution is identically concentrated at the filling inlet and at the drain valve at the furthest point in the sprinkler line. Retest the concentration level during the annual inspection of your sprinkler system.

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