MIC and your Sprinkler System: Identification and Prevention


General corrosion affects pipe gradually and consistently but does not pose an immediate threat to the metallic system. Corrosion does threaten a system, however, when it’s accelerated and localized by colonies of bacteria.

Microorganisms accelerate corrosion by rapidly diminishing pipe material at distinct, concentrated points. This process is referred to as microbiologically influenced corrosion (MIC). The MIC process, generates debris and leaks, eventually causing premature failure of a system.

A standard sprinkler system with proper maintenance will typically last over 50 years before needing major repairs. Unfortunately, the untreated presence of MIC can ruin a system much earlier. In severe cases, MIC can ruin a system in just 5 years.

What Constitutes Premature Failure?
A system fails prematurely for two reasons:
-The system has pinhole leaks that require component replacement.
-The system cannot operate as designed to achieve fire control.

MIC creates an uneven internal surface, produces clogging debris and bores holes within pipe. These three effects of MIC will alter the intended pressure within a system and cause its premature failure.

Pipe surface texture is critical in sprinkler system effectiveness. Any increase in roughness increases the pressure loss in each foot of sprinkler pipe. Even a small amount of internal corrosion, especially in main feed areas, could potentially make a system ineffective in fire control.

Where in the System is MIC Predominant?
Corrosion occurs in a system where air and water meet. In wet pipe systems, corrosion occurs most frequently where air is trapped. In dry pipe systems corrosion always occurs under pools of trapped water.

When the Corrosion Rate Increases
Introducing air into a wet system refreshes the oxygen corrosion reaction process. Every time a wet pipe system is drained and refilled the corrosion rate accelerates. The corrosion rate doubles for every 18 degree Fahrenheit increase. The higher the temperature of the system the faster the corrosion rate.

When the compressor in a dry system runs, it reintroduces warm, moist oxygen into the system piping. This humid air is a feast for the microorganisms that cause MIC.

Detection and Treatment
Treatment options include:
1. System Cleaning- Having your system cleaned is a good choice if the corrosion has not greatly altered the pipe surface.
2. System Replacement-If the damage is bad enough, your system will need to be replaced.

MIC test
MIC test

1. Drain and refill your system as infrequently as possible. Only test according to the required minimum. Tests introduce fresh nutrients and oxygen that help bacteria flourish.
2. Have leaks or weeping at joints and/or abnormal pressure inspected. They are a good indication of the presence of MIC.
3. Design for MIC prone areas to have thicker pipes. This method won’t prevent MIC but it will buy time until a standardized prevention method is determined.
4. Keep an eye on MIC prone areas of your system.
5. Get a lab test of the water supply to identify the microorganisms present.
6. Replace excessively corroded pipe.
7. Clean your system of MIC causing microorganisms using chemical injection methods.

Find More Information
For more details and to ask any questions about MIC you can reach an expert by clicking here .

Joseph Reynolds
Joseph Reynolds

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Posted on: June 10, 2015

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