“Antifreeze” can present hidden hazard to sprinkler systems
Like a parachute, a wet-pipe sprinkler system must work when it’s needed. If part of such a system is exposed to outside elements, the entire sprinkler system can become inoperable or cause burst pipes if unprotected against freezing temperatures.
To avert this possibility, it is recommended that “antifreezing” solutions be mixed with the water in the line to lower the freezing point of the fluid below the lowest anticipated outside temperature.
A key question: Should you be concerned about the type of antifreezing solution used? YES!
Ed Ford, a supervisor in the plant engineering and maintenance department at Saint Mary’s Hospital in Grand Rapids, Ml, offers this advice: “Don’t use an automotive antifreeze. Over time, it can turn into a foul-smelling, dark grey sludge that can become so thick it clogs the sprinkler heads.”
The use of automotive antifreeze in the hospital’s sprinkler system was discovered during a detailed system check. Ford explains: “One loop in the sprinkler system leads to our receiving area that is exposed to freezing temperatures. Noting this, the fire marshal asked if we had installed an antifreeze solution and check valve in that part of the system. We had put in antifreeze several years ago, but were unaware that a check valve was required. The fire marshal explained that the valve was simply a safety precaution to assure that the antifreeze did not back up and contaminate the rest of the system. Of course, to install the valve we had to drain some fluid from that part of the system. That’s when we discovered that the automotive-type antifreeze had turned into a thick sludge.”
The hospital immediately shut down the system and cleaned out the entire section.
“This problem would probably have gone unnoticed until an actual fire incident,” says Ford. “Normal testing procedures don’t require us to activate the entire sprinkler system, which would obviously create a mess. Instead, we test farther back in the system where a valve is located. We merely shut the valve and check for system operation and pressure at that point. These tests didn’t uncover the problem because the sludge was on the other side of that valve.”
According to the Dow Chemical Company, automotive antifreezes generally are not designed for use in stagnant systems such as fire sprinklers, nor are automotive antifreezes designed to last much more than four years. The reason is that for automotive applications, antifreeze corrosion inhibitors usually contain silicates that can degrade and settle out of the fluid. The resulting sludge can block the openings in sprinkler heads and render a system inoperable.
For fire sprinkler systems, Dow recommends using an inhibited propylene glycol where systems are connected directly to potable water supplies. If the water comes from a non-potable source, an inhibited ethylene glycol can be used. These organic chemicals have a hydrocarbon base and the chemical inhibitors keep the pH of the glycol solutions from turning acid or alkali and corroding the piping system. Consider the high temperatures and turbulent flow conditions in a car engine as compared to the low temperatures and stagnancy of a sprinkler system.
Industrial glycols are easily monitored and maintained. By simply draining a small portion of the glycol solution from the sprinkler line into a tube and inserting a test strip (similar to litmus paper) you can tell in a matter of minutes whether the inhibitor in the fluid is still at its required level of effectiveness or if it has declined to any significant degree. To determine if the concentration of glycol is adequate, a commercial-type refractometer can be used. In either case, the glycol solution can be readily reconcentrated and/or reinhibited without having to replace the entire volume of fluid.
“The inhibited glycols may cost more than automotive antifreeze,” says Ford, “but that’s insignificant. The cost of cleaning a system just once far exceeds the price difference between the two fluids. More important, though, consider the risk to people and property. If it’s known that an automotive antifreeze has been used in a fire sprinkler system, I would urge replacing it immediately with the correct glycol solution. If you don’t know for certain what’s in the system, have it checked carefully and thoroughly. Although a sprinkler system appears to be in proper working order, it might, in fact, be totally inoperable.”
