A previous article, “Microorganisms in Plumbing Systems”, warned that under certain conditions microorganisms can grow out-of-control in plumbing systems. When this happens, a “biofilm” of microorganisms and acidic enzymes that they secrete can become attached to pipe walls (Figure 1). This can lead to:

• Increased metals concentration (such as copper, iron, and lead) in the drinking water that comes in contact with the affected pipe
• Pitting and pinhole leaks in metal pipe
• Increased possibility of water-borne illnesses from microorganisms that are toxic to humans

Stagnating or slow moving water with inadequate disinfection allows microorganisms to grow rapidly. Microorganisms also need surface area to attach to – the more surface area, the more colonies of microorganisms can attach and grow.

This article identifies critical locations in a plumbing system where microbiological growth and biofilm formation tend to start. These locations are important to keep in mind as methods to prevent microbiological growth are discussed in future articles.

 

Biofilm in a Residential Copper Pipe
The light coating on the pipe in Figure 1 is a biofilm. Not all biofilms look like this. But, the one in Figure 1 is smooth, thick, and tightly adhered to the pipe wall. 

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. If conditions are right in the plumbing system, the microorganism population will grow.

When private wells are 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 percolated down into the aquifer. Once in the well, microorganisms can form biofilms and attach to screens, casings, and piping. For this reason, wells should be cleaned periodically with high concentrations of chlorine solution. This is called shock chlorination and usually involves a solution of 200 to 300 mg/L free chlorine held in the well for twenty-four hours. Well owners may not realize the importance of this cleaning procedure and may neglect to have it done.

For buildings with water provided by a municipal or community water system, microorganisms are present in the water to varying degrees. In the drinking water industry, the emphasis is on microorganisms that are toxic to humans and can cause illness. However, the absence of illness-causing microorganisms in a water system does not mean that other microorganisms are not thriving. The lowest presence of microorganisms is found in municipal or community water systems where disinfection concentrations are maintained at effective levels and monitored throughout the distribution 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 water source 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 or community 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. This can lead to microbiologically influenced corrosion of the water service line with the effect of increasing metal concentrations in drinking water or creating leaks through holes in the pipe wall. Microorganisms from the biofilms can also be carried away by the passing water and taken into the building’s plumbing system to start new colonies.

Point of Entry Water Treatment

Water treatment is sometimes installed in buildings just as the water piping enters the building. This is called “point of entry” water treatment. Any water treatment device should be considered a critical location for microbiological growth in a water system for three reasons:

1. Many water treatment devices include tanks that hold a large volume of water. Depending on water usage in the building, water might stay in a water treatment tank for an extended period of time. This long residence time in slow moving water allows for the growth of microorganisms.

2. Along with the large volume of water in water treatment devices comes increased surface area. Many water treatment tanks are filled with particles that perform the water treatment, where the higher the surface area of the particle, the better the treatment. Examples of such particles are sand, ion-exchange resin beads, and granular activated carbon. The increased surface area gives great advantage to the attachment of microorganisms and the development of biofilms.

3. Any disinfection in the water that enters most water treatment devices is removed in the device. The disinfection might be removed because that may be the purpose of the water treatment device, like granular activated carbon filters. It might also be removed because the disinfection is used up fighting microorganisms that have already taken up residence in the device. With the disinfection gone, downstream piping is no longer protected against the microorganisms that are carried out of the water treatment device in the flowing water.

Water Softeners

Water softening is a type of water treatment device. It is typically installed farther downstream from the building’s point of entry, but all of the problems of microbiological growth discussed above affect water softeners.

In areas of the country where water high in calcium carbonate (also called “hard” water) is used, water softeners are needed to keep calcium carbonate out of hot water systems. This is because calcium carbonate can fall out of the water as solid particles that build up on heating surfaces. The energy required to transfer heat from the heating surface through the increasing layer of calcium carbonate and into the water becomes greater and greater. Therefore, it is more cost effective to remove the calcium carbonate before it enters the hot water system.

Unfortunately, if microbiological growth has occurred significantly in a water softener, the hot water system downstream receives microorganisms in the water and no disinfection to fight them.

Hot Water Systems

Hot water systems have some additional characteristics that encourage the growth of microorganisms. For example, if the storage tank is oversized for routine water usage, water is in the tank for an extended time, creating the conditions for microbiological growth. An oversized hot water storage tank is installed when there is an infrequent but large demand for hot water, such as for filling a large bathtub. When the tub is not in use, water has a long residence time in the tank making it prone to microbiological growth.

For large buildings, hot water recirculation systems are typically used so that hot water will be immediately received at each faucet, no matter how far away from the hot water storage tank. The recirculation system contributes to microbiological growth by adding more residence time and surface area to the plumbing system. It also helps to spread microorganisms from an infected site to other sites that have not yet been infected.

Point of Use Water Treatment

Water treatment devices at or near faucets are referred to as “point of use” water treatment. The same issues of microbiological growth can occur on those devices as discussed above. The good news is that there is little to no piping downstream of the device that can be affected by microbiological growth. The bad news is that the consumer is directly downstream of these devices. For this reason, the manufacturers’ instructions on equipment cleaning and replacement of filters must be followed closely.

Faucets

Biofilms can form upstream and inside faucets as with any surface area in a plumbing system. Faucets and associated upstream plumbing that are reached a long time after the water has entered the building have a greater potential for microbiological growth. Faucets and associated upstream plumbing that are used infrequently also have a greater potential for microbiological growth.

Summary

In a plumbing system, the conditions of water stagnation, high surface area, and lack of disinfection contribute to the possibility that significant microbiological growth and biofilm formation can occur.

This article has discussed critical locations in a plumbing system where microbiological growth and biofilm formation tend to start, beginning at the water source and continuing through the water service line, point of entry water treatment, water softening, hot water system, point of use water treatment, and faucets. These locations are important to keep in mind as methods to prevent microbiological growth are discussed in future articles.

ABOUT AUTHOR

Abigail F. Cantor, P.E., Chemical Engineer

Process Research Solutions, LLC
PO Box 5593
Madison, WI 53705

www.processresearch.net
Phone: 608.233.3911
Email: info@processresearch.net

Process Research Solutions, LLC is an engineering consulting firm specializing in water quality investigations for drinking water and industrial process water.

The company has also developed tools and protocols to proactively monitor and control water quality, lowering the chances of developing serious and expensive issues in water systems.

Data management computer software, My Monitoring Data®, has been developed by Process Research Solutions, LLC so that water quality and water system data can be quickly interpreted and utilized.

 

[vc_row][vc_column][vc_column_text]Everyone has heard about the story of the water quality issues in Flint, MI. Everyone has heard about the problems and who is to blame. But rarely do people here about the true heroes that are uniting to make a difference and help save the town. This is the story of the real heroes in Flint, The Plumbers.

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Watts now offers its innovative OneFlow anti-scale system for home applications, in 8-, 12- and 16-gallon-per-minute models.

OneFlow uses no salt and generates no waste water and requires no backwashing or regeneration or electricity. Its compact design saves space compared to traditional water softeners.

OneFlow uses a physical water treatment technology known as TAC, template-assisted crystallization. When water comes into contact with the OneFlow media, calcium and magnesium minerals in the water collect and combine, forming microscopic crystals. These inert crystals break away as they grow and remain suspended in the water and move harmlessly through plumbing, unable to form hard scale inside pipes or on appliances because of the physical OneFlow treatment.

FLINT, MI — Members of Plumbing Manufacturers International (PMI) hit the streets Saturday 300 strong to install donated faucets and other plumbing in homes of residents affected by Flint’s water crisis.

PMI members gathered at 7 a.m. at the UA Local 370 Union Hall, located at 5500 West Pierson Road in Flushing, on Saturday, Jan. 30. The members took the donated faucets and supplies, as well as Brita water filters provided by the state before beginning work in houses and apartment buildings throughout Flint.

“PMI is proud to join with its members and the UA to put our vision of safe, responsible plumbing into action,” said Barbara C. Higgens, PMI CEO and executive director in a statement. “We appreciate the generosity of our members, the UA plumbers, IAPMO and everyone else that is helping to assure safe drinking water for the residents of the Flint area.”

The 300 plumbers are from local unions from across the country.

Plumbers Kevin Kinasz, of Bridgeport, and Rob Johnson of Swartz Creek assisted a number of Flint residents with donated faucet installation, including Lawanda Asa.

Asa, 70, said she is grateful to have so much help, not only from the plumbers, but the country on the full for the city she calls home.

“People from all over the country, Canada, Cher, tons of organizations are sending trucks loads of waters and filters to us. I’ve even lost count on how many people are sending us water,” she said. “It just goes to show how giving American people are. People that don’t even know us, have never heard of flint before are at our side. We’re so very blessed that the American people have such big hearts.”

The humanitarian effort was coordinated by PMI and the United Association of Journeymen and Apprentices of the Plumbing and Pipe Fitting Industry (UA). The hundreds of faucets and other plumbing supplies to be installed in Flint homes were donated by PMI.

The types of faucets donated by PMI members include American Standard Inc., Delta Faucet Co., Kohler Co., Moen Inc., and Speakman Co.

Source: Hundreds of plumbers install faucets, plumbing supplies at Flint homes | MLive.com