New Signet Optical Dissolved Oxygen Sensor Features Expanded Communication Capabilities

GF Piping Systems has introduced the Signet 2610-41 Optical Dissolved Oxygen Sensor featuring expanded communication protocol capabilities. The 2610-41 Sensor utilizes optical technology to measure dissolved oxygen with high reliability and accuracy in a wide variety of applications.

The new sensor model incorporates the Signet Sensor System Link (S3L) digital communication link that allows direct connection to the Signet 9900 SmartPro® Transmitter Generation III as well as to the Signet 8900 Multi-Parameter Controller.  These connection capabilities provide enhanced system control and versatility.

The company’s Signet 9900 Transmitter Generation III supports the new sensor with a dedicated Dissolved Oxygen (DO) instrument that allows for selection of measurement type, ppm, percent saturation, or partial pressure of oxygen.  The transmitter also allows for setting of system specific parameters to increase the accuracy of the dissolved oxygen measurement.

“The 2610-41 DO Sensor when used in conjunction with the 9900 Transmitter, provides an excellent cost-effective dissolved oxygen monitoring system,” says Dave Vollaire, Instrumentation Product Manager.  “Plus, GF Piping’s optical dissolved oxygen technology requires no membranes or filling solutions that in other technologies need frequent replacing.  This helps reduce maintenance costs.”

The 2610-41 incorporates all the inherent advantages of the original model including rugged materials of construction that can withstand the harsh environments of both fresh and saltwater applications.  A built-in Modbus RS485 and 4 to 20 mA current loop outputs provide ease of interface to existing control systems. Operating capabilities feature a measurement range of 0 to 20 mg/L, 0 to 200% saturation, and accuracies of ± 0.1 mg/L for 0 to 8 mg/L and ±0.2 mg/L for 8 to 20 mg/L.  An optical sensor cap with built-in calibration eliminates the need for field calibration and has a one year lifetime compared to membrane life, which is typically three to six months.  The sensor is CE and FCC approved and available with two week lead-time.

The Signet Dissolved Oxygen Sensor is suitable for use in a wide range of applications including municipal and industrial wastewater treatment, drinking water reservoir monitoring, environmental water discharge monitoring and aquaculture and aquatic life support.

via New Signet Optical Dissolved Oxygen Sensor Features Expanded Communication Capabilities – GF Piping Systems.

By Dave Duren

Believe it or not…when I’m out in the field as I’m headed to San Diego right now…the most asked question I’ll get is “what exactly is softening?” And if they don’t asked…I’ll be bringing it up!

If you asked 99% of the legitimate water treatment companies and or manufacturers; they respond by saying…Water softening is the “removal of mineral” from the water….plan and simple.

And mineral for the purpose of this article is mostly calcium and magnesium.  (Other metals are also removed by the ion exchange process)I’m going to be talking about ion exchange process from here on out for clarification. So let’s review what is actually going on in that what softener. Inside of a water softener are millions of tiny beads that are man-made of a plastic material. They have a negative charge. Mineral has a positive charge. Water with mineral in it passed through the bed of “resin” and the mineral clings to these beads. As they cling, they release some sodium ions. This is where the term “exchange” comes into play. After a certain period of time the beads become full of mineral or as we say the bed becomes exhausted and it needs to regenerate. This process involves drawing a brine (“salty”) solution into the bed which flushes the mineral away and down the drain while allowing more sodium ions to cling to the beads to get ready for more actual softening.

There are basically three ways this whole process occurs. The first way is manually. Someone tells the unit the time when to start and stop. The second way is with an automatic time clock. The time clock is set to regenerate every certain amount of days. A couple of reliable industry valves have a 12 day wheel on them to control this period. This involves sliding out pins that trip the unit into the process every set amount of days, like every third day or so. The third and probably most popular these days is a metered system. This involves some type of water meter that will kick the unit into regeneration when a set amount of water has passed through it.

So to continue, if mineral is not REMOVED from water through ion exchange softening then some other method is used to try to prevent it from sticking to surfaces, (inside of pipes, inside of heaters and exchangers, showerheads, shower doors..etc.) And you might ask WHY it is sticking to surfaces anyway. This is due to the positive valence or polarity of the mineral itself. Many of the reputable companies use the term “Conditioning” or “Management” but do not say softening in their explanation as to how this gets done. So with that, I’ve broken this down into 4 general methods that are used although there may be other methods out there.

• Magnets and electricity
• Adding polyphosphates
• Creating acid water, mostly using citric acid
• Media based methods

Let’s talk about these in a general way. First magnets and electricity are merely an attempt to change the polarity of the mineral elements in the water. They are not easily changed and many revert back to their original state if ever changed in the first place.

Secondly are polyphosphates. They have been around a good long while. This product coats the inside of the pipes and anything downstream with a thin layer of itself situating itself between the water and surface. It also coats the mineral element and prevents it from attaching to other things. This method is good in some applications.

Thirdly, acid water created by using citric acid or other chemical is added to the water to reduce the ph of the water making it “acidic”. Acidic water then has a tendency to make the mineral not want to stick to surfaces. This method can work at times but also reduces all of the water’s ph and now introduces acid water to the entire plumbing system.

The fourth method is using medias. There are a few different ones on the market and they basically create an atmosphere wherein that the mineral either sticks to it or sticks to itself or another particle of something that is introduced into the water.

None of the above methods removes or even reduces mineral from the water but once again, merely tries to “control” the mineral’s positive polarity and prevent it from sticking to surfaces. Either inside the plumbing system on a surface (shower doors, dishes, showerheads, etc.) Some with some success and others with zero success. This is why “SALT-FREE SOFTENING” does not exist except in a few extreme cases using very expensive equipment and seldom seen in residential applications.  It is also worth mentioning that NSF, National Sanitation Foundation and WQA, Water Quality Association both have standards and protocols for testing Ion exchange softeners. So as I’ve stated before, this is a very good way to tell if the equipment you’re being asked about or you yourself is trying to sell, is legitimate. Going to either website would also be a great way of learning more about what they do as organizations.

All of the above areas would command their own article or series of articles so take this as an overview. I think that you as a contractor need to at least be aware of the terms and methods because you will probably be asked by a customer. I think that when asked “what is softening?” you can simply say….”it’s REMOVAL of mineral from the water and the best and most economical, tried and true method is an ion exchange softener. I think it would be perfectly OK for you to tell your customer “Buyer Beware”…especially if they are asking or maybe even trying to tell you about some super wiz product they found on the internet or so slick guy called and tried to sell them over the phone.

I’d like to add that research and development continues to look for another method of SOFTENING water for residential use that will be efficient and affordable (which is what?….RIGHT!…REMOVING MINERAL FROM THE WATER!) as growing demand for this type of system exists. Until then ion exchange softening is the way to go to get the desired effects of actual SOFT WATER.  Until next time…happy selling!

Microorganisms: The effects of on-site water treatment
by Abigail Cantor, P.E.

This article is part of a series discussing the growth of microorganisms in plumbing systems.  As previously noted, many types of on-site water treatment equipment create conditions for microorganisms to grow and thrive by increasing the residence time of the water in the plumbing system with extra water storage volume, providing additional surface area for microorganisms to form biofilms on, and removing or using up any available disinfection to fight microorganisms.

The best practice in plumbing design is to provide on-site water treatment only when it is absolutely necessary to do so.  It is also important to select the appropriate treatment system, to determine a proper location for the equipment in the plumbing system, and to size the equipment so that volume and surface area are minimized.  Finally, automatic clean-in-place systems or manual cleaning protocols must be utilized to keep the equipment free of biofilms.

Determining Necessary Water Treatment

The first step in plumbing design is to determine specifically what contaminants, if any, are of concern in a building’s water source.  To do this, one must consider that there are numerous chemical compounds and types of microorganisms that can potentially contaminate drinking water.  Contaminants are identified and regulated in the United States with separate standards for municipal water systems, private water systems, and bottled water.  See Table 1.

If the building is connected to a public water system, the water has already been rigorously tested for the list of contaminants listed in Tables 2 and 3.  The results of those tests are public record, available at the regulatory agency that governs the state or territory where the building is located.  The results are also sent to each water utility customer annually in the Consumer Confidence Report.  There might be local issues to be concerned about, such as increasing concentrations of an industrial chemical in a public well.  In that case, the property owner should keep track of water utility plans to resolve the problem and attend water commission meetings, read the water utility website, or call the water quality manager.  If a building owner is not comfortable with the utility’s approach to removing the contaminant threat, then an on-site water treatment device should be used for removal.  It would be a rare and special case to need such a device.

It is possible for building plumbing systems to receive debris from municipal water distribution system piping.   Debris occurs in the distribution system when particles, like sand, settle out and when dissolved chemicals in the water, like manganese, iron, or aluminum, chemically precipitate out.  The possibility varies with the nature of the water and the water utility’s pipe cleaning and replacement program.  Debris can temporarily be entrained in the water during utility or road construction; it can happen seasonally due to water main flushing and other routine maintenance activities.  If a property owner experiences discolored water at an intolerable frequency, then on-site removal of the debris may be desired.

There is also the possibility that a building’s plumbing system leaches contaminants into the water.  Lead, copper, and iron are known to transfer from piping materials into water to varying degrees depending on characteristics of the individual water system.

If the property owner owns the water source, such as a private well, they must take the responsibilities of a water utility manager.  After complying with any state regulations on water quality for private water sources, the property owner must decide what other contaminants they might want to test for and, if significant, remove.  See Tables 2 and 3.  A common issue for private wells is high iron concentrations which can precipitate out and stain sinks and laundry.

For both private water sources and municipal water, the hardness of the water can be an issue.  Water hardness is mostly a measure of calcium and magnesium concentrations in the water.  Depending on other characteristics of the water, including temperature, the calcium and magnesium can precipitate out of the water as solid compounds.  The solids can cover heating surfaces in hot water heating systems, which in turn, will require more energy to heat the water; the buildup of solids will also reduce the life of the hot water heating tank.  For this reason, it is more economical to remove hardness from water where hardness is greater than about 120 mg/L as calcium carbonate (7 grains of hardness). Many people argue that hard water for cold domestic use should be softened; they state that hard water will clog pipes, create spots on glass shower doors, and react with soap so that it will not lather.  These are debatable arguments.  Even in locations with very high hardness (300 to 500 mg/L as calcium carbonate or 17.5 to 30 grains), cold un-softened water does not typically cause these severe problems.  Older residences in those locations only use softened water for the hot water system.  It is only recently, with modern plumbing practices, that cold water is also softened.

Determining Type of Water Treatment System

When specific contaminants have been identified in the water, then the proper contaminant removal technique can be selected.  The proper technique is the one that removes all contaminants of concern at the highest efficiency for the lowest financial and environmental costs.  Below are descriptions of common on-site treatment techniques.

Activated carbon filters

Activated carbon is carbon, typically from charcoal, that has been processed to make it very porous.  The more pores in the carbon, the higher the surface area.  The higher the surface area, the more specific contaminants can be pulled from the water to adhere to the carbon, a process called “adsorption”.

Different chemicals have different attractions to the carbon.  For example, heavier compounds have a greater attraction than lighter compounds.   This means carbon filters will not remove every type of contaminant.  In addition, the carbon can become saturated with contaminants and stop removing them.  Most importantly, just before the saturation point, the concentration of contaminants in the water flowing out of the filter begins increasing at a rapid rate.   Therefore, a carbon filter must be removed before the “breakpoint” of the least adsorptive contaminant or else the consumer will be drinking high levels of the contaminant that they intended to remove.  Filter manufacturers make assumptions as to what contaminants might typically be in water and set a common time when filters should be changed.   This may or may not be applicable in individual water systems.

Some carbon filters, such as certain ones that attach to sink faucets, are manufactured so that they combine treatment techniques within a small block of carbon.  Like other activated carbon filters, they have their limitations as to what contaminants can be treated and for how long.  In addition, the filters, themselves, can add contaminants to the water, based on compounds in the manufactured filter material.   There are research projects looking into this phenomenon.

Reverse osmosis and other membrane technologies

Reverse osmosis is a treatment technique that places a membrane barrier in the water.  The membrane is made of synthetic organic materials that do not have straight-through pores like a filter.  Instead, the pores are like a microscopic maze that can prevent many dissolved contaminants from passing through.  High pressure on the upstream side pushes the water, minus many of the contaminants, through the membrane.

There are other membrane technologies where the pores are straighter but very small.  Those technologies remove specific contaminants at lower pressures than reverse osmosis.

Membrane technologies prevent a percentage of the incoming water from going through the membrane, and instead, the water is sent down the drain to waste with the rejected contaminants.  The technique is not practical when it is too expensive to waste a percentage of the available water.  In addition, the synthetic organic membranes can dissolve in contact with some chemicals that might be in the water.  Chlorine used for disinfection is one of the chemicals and it is typically removed in a carbon filter upstream of the membrane.

Physical filters

Physical filters provide a physical barrier that can remove particles from water.  The filters can be made of sand or flossy material that will not allow particles of a certain size to pass through.

Ion exchange/water softeners

Ion exchange is a treatment process where one ion is taken out of the water and others are put into the water in its place.  An ion is an atom or molecule with either additional electrons or missing electrons; this gives the atom or molecule a negative or positive electric charge.   Water softeners are an example of an ion exchange process.  Here, calcium and magnesium, dissolved in the water as positively-charged ions, are “stuck to” negatively-charged ions.  When in contact with the ion exchange material, they are attracted and adhere to the material.  In exchange, the material releases two sodium ions for every calcium or magnesium ion; the sodium ions, then, form a union with the negatively-charged ions that were left behind in the water.  In the case of softening, the sodium concentration increases in the water.

At certain intervals, the ion exchange material must be cleaned to knock off the exchanged ions and replenish the original type of ions on the material.  In the case of water softeners, a solution of sodium chloride (brine) is used to flush out the ion exchange material.  This regeneration process creates a waste stream of chloride-laden water that is sent down the drain and out to the wastewater treatment plant.

Iron and manganese removal

Dissolved iron and manganese in the water eventually react with an oxidant like oxygen or chlorine in the water and precipitate out as a solid on pipe walls, sinks, and laundry.  To remove dissolved iron and manganese before it drops out elsewhere, an oxidant is pumped or bubbled into the water.  After a certain contact time, the iron and manganese are oxidized to a solid form and the particles are filtered out in a sand filter.

The filter must be backwashed periodically to clean the solids out and send them in a waste stream down the drain.

Sequestering

Sequestering is used to hold metals like iron and manganese in the water and prevent them from precipitating out as solids.  Traditionally, polyphosphate chemical products have been used in water systems to hold the metals in the water.  This is especially done when a small water utility or private property owner cannot afford a treatment process to remove iron and manganese.

It is now known that the use of polyphosphates carries negative side effects.  The polyphosphates not only can hold iron and manganese in the water but can also pull lead, copper, and iron from pipes and hold those metals in solution as well.  The consumer drinks any concentration of the metals being held in the water.  Polyphosphates also provide an essential nutrient, phosphorus, for the growth of microorganisms and in doing so, can aid in biofilm formation.  Finally, as the phosphorus from the polyphosphates eventually flows to waste, the wastewater treatment plants struggle with meeting stringent phosphorus discharge limits.

Disinfection

This series of articles on the growth of microorganisms and the formation of biofilms in piping systems has emphasized that disinfection of water is a main weapon against microorganisms.  With a clean piping system, it typically only takes a low dose of disinfection (0.3 to 0.5 mg/L free chlorine) to fight off intruding microorganisms and keep the piping system clean.

When on-site water treatment systems remove or use up disinfection in the incoming water, a dosing system should be added to replenish the disinfection in the water.  For owners of private water sources, continuous disinfection of the water before and after any treatment should be considered.

Some people complain about the taste of chlorine in their water.  If that is in issue, then drinking water can be left in a big pot open to the air or with cheesecloth covering it to allow the chlorine to transfer from the water into the air.  Alternatively, chlorine can be removed by a carbon filter at the drinking water faucet.  (Refer to the carbon filter discussion above.)

A more serious negative effect of disinfection is the possible formation of carcinogenic disinfection by-products.  This can occur when the water has high naturally-occurring organic carbon compounds that react with the chlorine.  If water is received from a municipal water system, disinfection by-products are tracked and minimized by regulation (Table 2); the property owner should re-chlorinate water within the concentration boundaries of the municipal utility.  For private water sources, the owner should become familiar with the disinfection by-product forming potential in the water and chlorinate accordingly.

Determining the Location of the Water Treatment System

Treatment systems located at the point in the plumbing where the water enters the building is called a point-of-entry water system.  Treatment systems located at the drinking water faucet are called point-of-use systems. The location of on-site water treatment in a building’s plumbing system is a critical design decision.

Point-of-entry systems treat the complete water flow to the building and are subsequently larger in size than point-of-use systems.  This creates a greater possibility of biofilm formation in the treatment equipment from increased surface area and retention of water.  It also increases the volume of water needed to clean and maintain the treatment system.  Many point-of-entry systems remove or use up incoming disinfection and so all of the piping downstream of the treatment system is not protected from the growth of microorganisms unless a disinfection dosing system is added.

Although smaller with little or no waste streams, point-of-use treatment systems must be installed for every drinking water faucet, while point-of-entry systems are installed at one location only.

Water treatment equipment for specific needs, such as water softeners for hot water, should be located as close to the specific need as possible.  Water softeners are typically located in a mechanical room adjacent to the water heating system.

Sizing Water Treatment Equipment

The goal of proper modern plumbing design should be to minimize volume of water retained and surface area of the treatment equipment.  The larger the size of the water treatment equipment, the more volume of water is retained on-site and the more surface area is available for biofilm formation.    As already discussed, one way to minimize volume is to eliminate treatment equipment unless absolutely necessary.  In addition, the volume of water to be treated should be carefully considered.  Divide the estimated total water use into: water for drinking/cooking, water for cleaning, and water for any significant purpose such as filling large bathtubs.  Design separate pipelines and treatment strategies for each purpose.

Cleaning Water Treatment Equipment

Various types of water treatment systems have cleaning cycles.  Sand filters must be backwashed to remove trapped solids.  Ion exchange material must be backwashed to remove solids and must be regenerated to replace ions.  Water treatment of this type has automatic clean-in-place cycles.  The cleaning water can be chlorinated to disinfect and fight developing biofilms routinely.  It is critical to work with the equipment manufacturer in setting up a cleaning water disinfection system; chlorine in too high a dose can destroy the treatment material.

Filters that require replacement of filter cartridges should be changed before or at the time recommended by the manufacturer to prevent breakthrough of contaminants and the development of biofilms.

Summary

This article continues the series warning against the growth of microorganisms and the formation of biofilms in plumbing systems.  On-site water treatment systems can contribute to the growth of microorganisms by increasing  the retention time of water, increasing the surface area where biofilms can form, and by removing or using up disinfection in the water.

The first step in plumbing system design is to determine which contaminants in the water are essential to remove on-site.  In many buildings that receive municipal water, additional water treatment is not necessary.  There is a greater need for on-site water treatment when the building is served by a private water source where the property owner must manage their own personal water utility.  There are also special needs for water treatment such as the need to soften hard water before it enters a hot water heating system.

After it is determined what contaminants must be removed, the best removal system must be selected.  Every treatment system has advantages and disadvantages and has specific removal efficiencies for each individual contaminant.   The sizing of the water treatment equipment and its location in the plumbing system are also critical design choices affecting the growth of microorganisms.

Finally, all water treatment equipment must be cleaned and disinfected or filter cartridges replaced routinely to clean out and prevent the formation of biofilms.

Maintaining a high water quality, including the elimination of microbiological growth, is a very delicate balancing act that should be given the highest priority when designing a plumbing system.

Responsibilities in preventing microbiological growth in plumbing systems
by Abigail Cantor P.E. (Chemical Engineer)

This article describes the responsibilities in preventing microbiological growth from occurring in plumbing systems.  Those responsibilities are shared by the Plumbing Designer, the Building Contractor, the Municipal Water Utility Manager, and the Property Owner.

The Plumbing Designer

The prevention of microbiological growth in plumbing systems starts with the plumbing designer.  Two new design requirements must be met in order to prevent microbiological growth – the volume of water residing on-site must be minimized and the surface area that the water contacts must be minimized.  These design requirements must be balanced against the property owner’s list of desired plumbing fixtures and the plumbing code’s design criteria.

Considering the Number of Fixtures and Pipe Sizes

The property owner may have a long list of desired plumbing fixtures and showers with multiple sprays.  The plumbing code will base the size of the piping on the number of fixtures that can possibly operate at the same time.  The property owner needs to understand that there is a trade-off between having extra plumbing fixtures versus minimizing the volume of water stored in the piping.  The use of diverter valves as well as the property owner’s acceptance of fewer fixtures may assist in keeping pipe sizes smaller.

Considering Water Conservation Fixtures

Water conservation fixtures are becoming a necessity in some areas where drinking water resources are scarce.  With both new plumbing systems and the modification of existing plumbing systems, the lower water usage must be considered and the on-site storage of water be reduced accordingly.

Considering Tubs

The property owner’s selection of bath tubs and hot tubs will greatly influence the quantity of hot water that needs to be prepared and stored on-site.  The property owner needs to understand the trade-off between the number of tubs and the filling rate of each tub versus minimizing the volume of water stored on-site.

Tankless water heaters can be used to assist in lowering the volume of hot water that needs to be stored.  Acceptance of lower filling rates by the property owner will also help to lower the volume of hot water storage.

Considering Water Softening

With hard water, water softening is required before sending water into a hot water system.  Calcium carbonate from hard water will scale up the heating surfaces in the hot water system which will, in turn, increase the quantity of energy and the cost to heat the water.  The life of the hot water heating equipment will also be reduced with the build-up of scale.

However, water softeners increase both the volume of water stored and the surface area that the water is exposed to on-site.  They can become incubators for microorganisms.  If less hot water is required, then less water needs to be softened and the smaller the softener tank.  Again, the property owner’s acceptance of lower filling rates for tubs will lower the hot water volume requirement.

In addition, cold water does not need to be softened except in a few specific cases.  Water softeners can be smaller when only the water for the hot water system is softened.

Water softeners can also be outfitted with the dosing of chlorine and other biofilm-fighting chemicals to the brine tank so that disinfection of the media inside the softener tank can occur routinely and prevent the development of biofilms inside the tank.

Considering Other Water Treatment

A previous article pointed out that water should not be treated on-site unless absolutely necessary.  The article listed possible contaminants in water and steps to take in deciding whether or not removal of certain contaminants is necessary.

For every treatment device, water volume and surface area is increased in the plumbing system.  Each device must have a means of routine cleaning and disinfection, as was discussed with water softeners, in order to prevent them from becoming incubators for microorganisms and inoculating the downstream piping.

 

Considering Chemical Dosing into Piping

Water softening and other on-site water treatment devices can remove existing disinfection from the water.  Long residence times for water such as in hot water storage tanks also deplete the disinfection in the water.  Designers of commercial buildings where large volumes of water are required need to consider re-injecting chlorine or other biofilm-fighting chemicals approved for potable water after water treatment devices and before storage tanks.  A previous article described chemical dosing systems.

Some property owners, such as those with private wells, do not want to introduce disinfection because of its taste and smell in the water.  Disinfection chemicals can also form harmful by-products if dosed incorrectly.  But chemical disinfection, especially chlorine, is the most significant protection against the growth of microorganisms in modern water systems because of its disinfecting power at a reasonable cost and its ability to remain in the water to the far reaches of the plumbing system.

Considering Pipe Flushing Features

If high-volume, complicated plumbing systems are inevitable in a building, automatic pipe flushing should be considered.  Automatic valves can be placed at the ends of long pipe runs to move fresh water through the water line.  Such a valve needs to be slow-opening and closing so that water hammer does not occur as it does with a solenoid valve.  Also, this strategy wastes water which cannot be tolerated in areas where water resources are scarce.  Nevertheless, in some cases, automatic pipe flushing may be the only answer to keeping water fresh on-site.

Considering Sampling Taps

Small valves and faucets are inexpensive to install in pipelines.  Consider installing such taps before and after any water treatment or storage tank in the plumbing system so that water samples can be taken and the quality of water, as it changes throughout the plumbing system, can be monitored.  A previous article described critical locations in plumbing systems where microorganisms can grow.  This can be a guide for locating sampling taps.

The Building Contractor

 

The growth of microorganisms in plumbing systems begins during the building’s construction period when water pipes are filled with water.  The water usage, at that time, is not what the plumbing system was designed for and the water sits stagnant in the pipes for a long period of time.  Any disinfection in the water is quickly depleted.  Microorganisms can now thrive.  Building contractors should ensure and document that this does not occur on their watch.

Before a project begins, review the plumbing plans for the design features that have been discussed in these articles.  Every pipe run, water treatment device, and water storage tank has the potential for microbiological growth during the construction period.  Is there a way to monitor, flush, and disinfect each plumbing system feature during the construction period?  If not, work with the plumbing designer to provide the means to do so.

Before filling new pipes with water, make sure that they have been cleaned of debris and disinfected.

After filling new pipes with water, begin monitoring for and documenting chlorine concentration routinely and frequently.  A previous article describes how to do this with a relatively inexpensive field test kit.

Less frequently, monitor for microbiological activity.  A previous article described how to do this with water samples for Heterotrophic Plate Count (HPC) analysis.  Since that article was written, a better test has become commercially available.  It is a test for ATP and is described in a sidebar to this article.

Run treatment devices through their cleaning cycles on a routine basis during construction and refresh the water in piping and tanks.

The amount of plumbing system flushing can be reduced by dosing the water system with chlorine and biofilm-fighting chemicals used in potable water systems.  (See a second sidebar for a description of chemicals that can be used.)

Strategies to carry out these tasks in an economical fashion during construction need to be developed.  This is a new concept for the building industry, but it can and must be done based on the current knowledge about microbiological growth in water systems.

The Municipal Water Utility Manager

 

The role that microorganisms play in water systems is a new topic in the drinking water industry as it is in the plumbing industry.  Municipal water utility managers are just becoming aware that microorganisms and their biofilms can help to transfer piping metals like lead, copper, and iron to water.

Municipal water utility managers need to ensure and document that the water throughout the water distribution system stays properly disinfected and that microbiological activity is low.   Throughout the distribution system, managers need to:

• Monitoring for disinfection and microbiological activity
• Minimize water residence time (water age)
• Ensure a proper disinfection residual
• Perform uni-directional flushing on water mains to properly clean piping

Managers might want to refer to a Water Research Foundation report that demonstrates techniques to control water quality at the consumers’ taps (Project 4286: Distribution System Water Quality Control Demonstration).

Ironically, because of modern plumbing design practices, the growth of microorganisms can occur whether or not there is a high microbiological activity in the water entering a building.  However, water utility personnel should document that the municipal system did not contribute significantly to any building’s plumbing problem.

The Property Owner

 

Property owners need to understand the dilemmas in designing and installing modern plumbing systems as have been discussed in these articles.  That way, they can make better decisions in planning their buildings’ plumbing systems.

If a property owner uses a private well instead of municipal system water, that person must take on the responsibilities of a water utility manager.  They need to know what contaminants should be removed from the water and the best method of removal.  They also need to consider how to keep the water and the system disinfected.  They must monitor for disinfection and microbiological activity and ensure that their water system is operating safely.

Conclusions

 

Preventing the growth of microorganisms in plumbing systems is a new reality for modern plumbing systems.  There has not been a lot of experience in designing systems with minimal volume and surface area while still utilizing the new plumbing fixtures that are available today.  But, the plumbing industry can start by being aware of the microbiological growth issues and design dilemmas.  Eventually, people in the plumbing and construction industry will figure out how to accomplish this task economically and efficiently.

This pushes people away from techniques that they have always used and what they have always known to be true.  But, the industry must move in this direction or else the future will be filled with ruined plumbing systems in new buildings, angry property owners, and liability lawsuits for plumbing and building contractors.

This series of articles does not provide all the answers needed to tackle this problem; they were written to raise awareness of the problem and to encourage the plumbing profession to consider the repercussions of the volume of water stored on-site and the surface area that the water is exposed to.  The growth of microorganisms in plumbing systems can be prevented with everyone’s participation.

 

A New Method of Testing for Microbiological Activity

 

In a previous article, a method of measuring microbiological activity in water was presented.  It was a method to measure the number of heterotrophic bacteria colonies that can grow from a water sample (HPC analysis).  But, there are other types of bacteria in water besides heterotrophs.  Nevertheless, the HPC analysis was used because it was the only economical and commercially available test.

A new type of test now meets the economics of the HPC analysis.  It is a test for adenosine triphosphate (ATP), the energy molecule found in living organisms.  This test will measure the presence of any type of living organism in the water sample, not just heterotrophic bacteria.

Unfortunately, there are only a few laboratories and professors that have the equipment to run this test.  For example, only one small laboratory in Wisconsin can run the ATP test.  Nevertheless, it is worthwhile to pursue the use of this test by inquiring at commercial laboratories and by contacting major manufacturers of the equipment (http://www.luminultra.com/Industry-Applications/water-treatment.html).

New Chemicals to Clean Out Biofilms

Chlorine is the most common chemical used for disinfection of drinking water.  The chemical is effective in preventing biofilms from forming.  However, once the biofilms have formed, it is difficult for the chlorine to penetrate the biofilm and remove it from surfaces.  In addition, many modern plumbing materials cannot be exposed to high concentrations of chlorine, so dosages that can be used are limited.

There are new chemicals on the market that can penetrate and destroy biofilms.  For use in drinking water, the chemical must be approved by NSF International (http://nsf.org) as an acceptable additive.  When determining new chemicals to use for biofilm removal, look for the NSF approval and follow-up on references of organizations that have used the product.