What’s Bugging Your Pipes: How Microorganisms Affect Plumbing Systems
Published by:
Process Research Solutions, LLC
PO Box 5593
Madison, WI 53705
www.processresearch.net
Copyright © 2013 Process Research Solutions, LLC
ISBN: 9781619275164
Microorganisms are most likely to blame if your plumbing system has:
When these types of problems occur, someone gets blamed for them — from the plumbing designer all the way to the municipal water utility manager. But, everyone involved in a plumbing system’s development and operation can play a role in preventing the problems from occurring in the first place.
That is why this booklet is written for:
This booklet is a resource on microbiologically influenced corrosion for its understanding, prevention and remediation of the problems that are “bugging” your pipes.
Chapter 1
Introduction to Microbiologically Influenced Corrosion
Biofilm Photo Gallery
Chapter 2
Typical Locations of Microbiological Activity in Plumbing Systems
Chapter 3
On-Site Water Treatment System Design to Minimize Microbiological Activity
Chapter 4
Plumbing System Design to Minimize Microbiological Activity
Chapter 5
Fighting Microbiological Activity and Biofilms
Chapter 6
Routine Monitoring of Water Quality
Chapter 7
Responsibilities in Preventing Microbiological Growth in Plumbing Systems
Appendix A: Drinking Water Regulations
Appendix B: Pipe Scouring Velocity and Water Flow Rates
Appendix C: Disinfection Concentrations
About the Authors
Acknowledgements
This story is repeated over and over: Occupants of a new building notice discolored water coming from the water faucets or, perhaps, a “rotten egg” odor coming from the hot water.
What will happen next is that the plumbing contractor, realizing corrosion of metal plumbing system materials is occurring, will pull the sacrificial anode rod from the hot water storage tank. This rod, with special metallic properties, is there to slowly corrode over many years and sacrifice itself to corrosion in order to protect the storage tank. But, in these cases, the anode rod has greatly corroded over a few weeks or months. The plumbing contractor will replace the rod, only to see the new rod corrode quickly again.
Stray electrical currents or the connection of dissimilar metals, both problems that can occur in localized areas of the piping system, are then blamed for the system-wide corrosion. Wires are added to connect various parts of the piping system for diverting electrons to a different path.
The problem persists.
What most people don’t know is that the problem is typically of microbiological origin. Microbiologically influenced corrosion (also known as MIC) has not been appropriately understood or acknowledged in the drinking water industry — both in municipal water systems and in plumbing systems.
But, microorganisms are everywhere. And, there are many different types of them. Some directly cause human illness but many others do not. These waterborne microorganisms can grow into out-of-control populations when there are long periods of water stagnation or low flow, and when disinfection chemicals are dosed in inadequate concentrations. Under such conditions, microorganisms attach to plumbing system surfaces. They secrete enzymes to form a protective barrier and begin to multiply. This buildup of enzymes and colonies of microorganisms on surfaces is called a “biofilm.”
The biofilm is acidic and can create conditions at the pipe wall that allow metal to corrode. Metals used in plumbing systems, such as copper, iron and lead, have been found with elevated concentrations in the drinking water when biofilms are present. The metal corrosion sometimes presents itself as discolored water. Pitting and pinhole leaks in pipe walls have also been found.
In addition, chlorine and other disinfectants cannot reach the microorganisms protected in the biofilms. Instead, disinfectants get used up by reactions with the surface of the biofilms and with the metallic corrosion debris on the pipe walls. This creates a low-disinfection environment that has no ammunition to fight off the continued growth of microorganisms — including those, if they are present, that are toxic to humans.
Raising awareness of microorganisms and their biofilms, which play this significant role in our water distribution and plumbing systems, is the main purpose of this booklet. This booklet also summarizes methods to monitor, prevent and remediate microbiologically influenced corrosion.
Under certain conditions, microorganisms can grow out-of-control in plumbing systems. When this happens, “biofilms” of microorganisms and acidic enzymes that they secrete can become attached to pipe walls. This can lead to:
All photos are provided courtesy of Process Research Solutions, LLC.
Interior of pipe with corrosion debris
Interior of pipe with corrosion debris removed exposing pits
Interior of pipe with corrosion debris removed exposing pinholes
Exterior of pipe showing pinholes that started from the interior of the pipe
Where can microbiological activity and biofilms develop in a plumbing system? That’s like asking: Where does an elephant sit? The answer in both cases: Anywhere they want to.
THE WATER SOURCE
A biofilm problem in a building can start with the water source. The water can carry microorganisms into a building’s plumbing system, where if conditions are right, the microorganism population will attach and grow.
When private wells provide a building’s water source, microorganisms can enter the well in the groundwater, which has had contact with the surrounding soil and sometimes with surface water that has entered into the underground aquifer.
For municipal surface and ground water sources, microorganisms can be present to varying degrees depending on environmental circumstances as with private wells. The fate of microorganisms from a municipal water source to the entrance of a building depends on the nutrients (that is, food for microbiological growth) available in the water, the amount of disinfection chemical added and the residence time in the water distribution system. Also, when water distribution system piping already has a build-up of chemical scales, biofilms and corrosion debris, the disinfection chemical is consumed quickly and is not available to fight microorganisms.
The lowest presence of microorganisms is found in municipal water systems where water distribution pipe walls are clean and disinfection concentrations are monitored and maintained at effective levels throughout the system. There are some water systems where disinfection is not maintained sufficiently and some where no disinfection is added at all. In those systems, the presence of microorganisms entering a building can be quite high.
THE WATER SERVICE LINE
A building is connected to a source of water by means of a water service line. This can be piping between a building and a privately-owned well; or, it can be piping between a building and a water main in a municipal water distribution system. The longer that water stays in the water service line, the more likely it is that microorganisms will form biofilms on the pipe walls. Microorganisms from the biofilms can then be carried away by the passing water and taken into the building’s plumbing system to start new colonies.
POINT-OF-ENTRY WATER TREATMENT