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Corrosion in fire sprinkler piping

Corrosion in Fire Sprinkler Piping – by Tom Hartel.

You work diligently to protect your building from fire. You install a quality sprinkler system with state-of-the art piping and heads. You conduct regular inspections. Then a fire breaks out and your system fails.

The tiny, but very aggressive cause may be hidden inside your pipes: bacterial microorganisms that cause corrosion known as Microbiologically Influenced Corrosion.

Reports of MIC in fire protection systems have grown significantly over the past decade. Newer systems, which employ a broader variety of piping materials, can be the most vulnerable.

Various industries, such as power utilities, have established extensive water treatment programs and
procedures to tackle MIC. The National Fire Protection Association (NFPA), together with water, bacteria, and metallurgical experts are aware of the surge in recent MICrelated activity, and are working to develop effective management and inspection guidelines, standards, and solutions.

The problem is exacerbated by MIC’s aggressiveness, which can penetrate pipes in just a few months. Once the MIC bacteria attaches to the metallic components, it grows rapidly and, to the untrained eye, spreads undetected.

MIC affects a variety of materials (steel and copper), systems (wet and dry), and geographical areas across North America. In recent years, it has become one of the primary concerns of the fire protection industry.

In 1998, a nursing home in Iowa experienced a situation where the sprinkler heads failed to release water during a fire, due to their being totally plugged with thick rust deposits as a result of MIC. Also, a very large, federal government research facility in Illinois has a well documented case of MIC pinhole leaks in one of the cooling water systems, and the National Fire Sprinkler Association has documented more than two dozen cases of MIC in their technical report dated June 1998.

What is the origin of MIC?

The MIC experts report that hundreds of different microbes exist in typical municipal water systems, offering the potential for numerous destructive combinations.

MIC contamination is more powerful than typical corrosion because it is concentrated in the piping and therefore can accelerate its growth and create high-activity pockets.

The results can be extremely acidic, wearing away material to create extensive pinhole leaks. As salt and iron deposits build, loose debris can reduce or plug the sprinkler flow.

Fire protection systems offer a conducive environment for bacteria through the process of draining and refilling the water supply, which introduces new oxygen and bacterial nutrients into the piping. Untreated water, pipe joint compound, and oils in the piping all provide ingredients for microbiological growth.

Experts suggest that the presence of MIC can be identified by orange or black tubercles or black mud-like slime in steel pipe, and blue or green tubercles in copper pipe.

The costs associated with repairing a full-blown MIC infection can be very high. Accordingly, controlling and minimizing the threat of MIC before it has a chance to gain strength and extend its reach is the most cost effective course.

Continued management of MIC

While MIC continues to receive a great deal of study, the full scope of the scientific reasons for its rapid rise aren’t fully known. Under the circumstances, the best offense is clear: a strong defense.

Regular monitoring of pipe characteristics by a trained professional is recommended to identify and manage bacteria levels and activity. Inspections can also detect associated debris, obstructions, and similar indicator conditions. A sample of the corrosion by-product can be submitted to a laboratory for testing to identify the microorganism(s) present.

When MIC is discovered, the system should be cleaned, either mechanically (off-line) or with chemical cleaning, depending on the extent of corrosion. All possible water supply sources should be tested for bacteria presence. If corrosion is excessive, the affected pipe sections need to be replaced.

Additionally, several corrosion management companies have designed self-contained automatic chemical delivery systems and corrosion monitoring stations that are manufactured specifically for fire sprinkler systems.

These corrosion experts also offer an on-site internal pipe video inspection, as well as non-invasive, ultrasound pipe scanning services.

The chemical industry has adopted some biocides (liquid corrosion inhibitors) for managing and mitigating MIC. However, because of their poisonous nature, the biocides must be treated carefully by trained experts. The Environmental Protection Agency (EPA) requires these chemicals to be registered and used under specific guidelines. Furthermore, too much exposure to biocides can create immunity within the MIC bacteria community. The biocides must be rotated by a qualified expert on a regular schedule to be effective.

To avoid the expense of continually treating a recurring MIC problem, engaging a qualified corrosion control expert is essential in preventing further contamination. Since fire protection systems have flow rates unlike other industries dealing with MIC, it is also advisable to engage a fire protection professional familiar with the overall sprinkler system operation and maintenance.

Preventing reoccurrences may require altering one or more environmental conditions inside the pipe such as: oxygen levels, pH, temperature or residual chlorine content.

Taking action against MIC

The National Fire Protection Association (NFPA) has revised its inspection standards to address MIC infection and established an “MIC Task Group” dedicated to developing guidelines for sprinkler system  design, installation and practices to mitigate MIC growth.

Moreover, several sprinkler pipe manufacturers are now coating the interior surface of their pipe with a biofilm which will resist microbial colonization and deter biological growth. These biofilms are very new and their effectiveness has not been tested over long periods of time.

The NFPA is also researching technological advances in the manufacturing of a new sprinkler pipe that is resistant to MIC. Fire Protection Installation and Maintenance Contractors are pressing for their recommendation on the appropriate pipe for installation and replacement.


To face the MIC problem, fire protection contractors need to work closely with building owners and managers to preserve the integrity of the fire protection systems for the long-term.

Fire protection systems — like an airplane, boat, and most mechanical equipment — require maintenance appropriate to the circumstances. With life safety, significant property loss, and potential business disruption at risk, a high standard of care is warranted.


The information contained in this article was compiled from authoritative sources and is intended for use as a reference guide only. We have made every effort to provide quality information, but we make no claims, promises, or guarantees about the accuracy or completeness of the content of this article.

Fire Protection Contractors are neither scientists nor experts on MIC. Accordingly, we are concerned that standards and solutions for managing MIC are forthcoming as soon as possible. In our system inspection services, we perform testing to verify that the system is operational to the requirements of the local fire prevention authority. If, in the process of this work, we encounter a condition that may indicate a possible MIC agent, we promptly inform our client and assist them in engaging a qualified corrosion expert to undertake an examination of the system and determine the scope of the necessary remediation.