• Sign In
  • Create Account
  • Sign Out
  • My Account
  • NEWS
  • PRODUCTS
  • CONTRACTORS
  • ENGINEERS
  • RADIANT & HYDRONICS
  • INSIGHTS
  • MEDIA
  • RESOURCES
  • EMAGAZINE
  • SIGN UP!
cart
facebook instagram twitter linkedin youtube
  • CONTRACTORS
  • BATH & KITCHEN PRO
  • BUSINESS MANAGEMENT
  • HIGH EFFICIENCY HOMES
  • TECHNOLOGY
  • WATER TREATMENT
  • PMC COLUMNS
  • PMC COLUMNS
  • Dave Yates: Contractor’s Corner
  • John Siegenthaler: Hydronics Workshop
  • Kenny Chapman: The Blue Collar Coach
  • Matt Michel: Service Plumbing Pros
  • Scott Secor: Heating Perceptions
  • ENGINEERS
  • CONTINUING EDUCATION
  • DECARBONIZATION | ELECTRIFICATION
  • FIRE PROTECTION
  • GEOTHERMAL | SOLAR THERMAL
  • PIPING | PLUMBING | PVF
  • PME COLUMNS
  • PME COLUMNS
  • Christoph Lohr: Strategic Plumbing Insights
  • David Dexter: Plumbing Talking Points
  • James Dipping: Engineer Viewpoints
  • John Seigenthaler: Renewable Heating Design
  • Lowell Manalo: Plumbing Essentials
  • Misty Guard: Guard on Compliance
  • RADIANT & HYDRONICS
  • RADIANT COMFORT REPORT
  • THE GLITCH & THE FIX
  • INSIGHTS
  • CODES
  • GREEN PLUMBING & MECHANICAL
  • PROJECT PROFILES
  • COLUMNS
  • SPONSOR INSIGHTS
  • COLUMNS
  • Codes Corner
  • Natalie Forster: Editorial Opinion
  • Guest Editorial
  • MEDIA
  • PODCASTS
  • VIDEOS
  • WEBINARS
  • RESOURCES
  • INDUSTRY CALENDAR
  • DIRECTORIES
  • EBOOKS
  • PM BOOKSTORE
  • CE CENTER
  • MARKET RESEARCH
  • CLASSIFIEDS
  • EMAGAZINE
  • EMAGAZINE
  • ARCHIVE ISSUES
  • CONTACT
  • ADVERTISE
  • PME EMAGAZINE ARCHIVES
search
cart
facebook instagram twitter linkedin youtube
  • Sign In
  • Create Account
  • Sign Out
  • My Account
  • NEWS
  • PRODUCTS
  • CONTRACTORS
    • BATH & KITCHEN PRO
    • BUSINESS MANAGEMENT
    • HIGH EFFICIENCY HOMES
    • TECHNOLOGY
    • WATER TREATMENT
    • PMC COLUMNS
      • Dave Yates: Contractor’s Corner
      • John Siegenthaler: Hydronics Workshop
      • Kenny Chapman: The Blue Collar Coach
      • Matt Michel: Service Plumbing Pros
      • Scott Secor: Heating Perceptions
  • ENGINEERS
    • CONTINUING EDUCATION
    • DECARBONIZATION | ELECTRIFICATION
    • FIRE PROTECTION
    • GEOTHERMAL | SOLAR THERMAL
    • PIPING | PLUMBING | PVF
    • PME COLUMNS
      • Christoph Lohr: Strategic Plumbing Insights
      • David Dexter: Plumbing Talking Points
      • James Dipping: Engineer Viewpoints
      • John Seigenthaler: Renewable Heating Design
      • Lowell Manalo: Plumbing Essentials
      • Misty Guard: Guard on Compliance
  • RADIANT & HYDRONICS
    • RADIANT COMFORT REPORT
    • THE GLITCH & THE FIX
  • INSIGHTS
    • CODES
    • GREEN PLUMBING & MECHANICAL
    • PROJECT PROFILES
    • COLUMNS
      • Codes Corner
      • Natalie Forster: Editorial Opinion
      • Guest Editorial
    • SPONSOR INSIGHTS
  • MEDIA
    • PODCASTS
    • VIDEOS
    • WEBINARS
  • RESOURCES
    • INDUSTRY CALENDAR
    • DIRECTORIES
    • EBOOKS
    • PM BOOKSTORE
    • CE CENTER
    • MARKET RESEARCH
    • CLASSIFIEDS
  • EMAGAZINE
    • EMAGAZINE
    • ARCHIVE ISSUES
    • CONTACT
    • ADVERTISE
    • PME EMAGAZINE ARCHIVES
  • SIGN UP!
Plumbing & Mechanical Engineer James Dipping: Engineer Viewpoints

James Dipping: Chemical and non-chemical additives for Legionella control

Specialty components to further reduce the risk of Legionella.

By James Dipping
Specialty components

HT Ganzo/iStock/Getty Images Plus via Getty Images.

January 6, 2023

Many of the topics I have discussed in my column to this point have been about temperature considerations within the supply and return system based on recommendations in the community and right-sizing domestic water piping to reduce the overall volume of water in the building’s piping system. We’ve even discussed increasing intelligence to commercial plumbing systems to improve water management programs and reduce liability concerns. And all this writing is for what? To reduce the risk of legionella bacteria developing in the domestic water system.

These topics fall under what I call the “must-considers” of plumbing engineering responsibilities. They might not be in line with a code minimum requirement, but as an engineering community, we have a responsibility to uphold the health and safety of the public. And as these topics can be applied most every building type, they must be considered for every building a plumbing engineer will design.

What I have yet to discuss is what specialty components we have at our disposal to even further reduce the risk of legionella bacteria gaining a foothold in the domestic water system.

There will be a series of topics forthcoming on what chemical and non-chemical additives, tools and technologies plumbing engineers can consider as “add-ons” in their design practice, and when to implement them.

In this article, we will look at chemical and non-chemical additives for legionella control. These are items that are directly added/mixed with the potable water in the piping network.

Before we delve into the water additives available, engineers must understand that the Environmental Protections Agency (EPA) plays a very significant role in regulating these systems. They state:

  • Adding certain water treatment technologies in a premise plumbing system could impact the chemical and microbial quality of the water and change the regulatory status of the premise plumbing system. The criteria for being a regulated PWS are provided at 40 CFR 141.3;
  • Facility owners or operators who are considering adding treatment to their building’s premise plumbing system may wish to consult with their water supplier (i.e., PWS) to better understand any potential water quality issues before making treatment-related decisions; and
  • In addition to the drinking water regulations under SDWA, manufacturers of pesticidal treatment technologies used to control Legionella and other microbial contaminants need to comply with the Federal Insecticide, Fungicide and Rodenticide Act (FIFRA) requirements, which are independent of the SDWA requirements.


As plumbing engineers, we cannot pretend to be experts in chemistry, which makes being experts in these systems very challenging. It is very prudent in these cases to leave it to the experts.


The full resource from the EPA can be found here. Much of the information below comes from the EPA’s document, and the many studies included in developing its document. As plumbing engineers, we cannot pretend to be experts in chemistry, which makes being experts in these systems very challenging. It is very prudent in these cases to leave it to the experts, and the excerpts below are to provide a high-level overview of the systems and some design considerations. I advise that the paper published by the EPA is read in full context for anyone seriously looking to include any system mentioned below in their design.

Another excellent resource soon to hit the market will be ASPE’s Design Methodology to reduce Rick of Legionella, of which I am a working group member. And now, on to the discussion….


Chemical chlorine or “free chlorine?”

Chlorine was first used in the U.S. as a primary disinfectant of drinking water in Jersey City, New Jersey, in 1908. Chlorine is added to drinking water as elemental chlorine (chlorine gas), sodium hypochlorite solution or dry calcium hypochlorite. Sodium hypochlorite is the species of chlorine most used by public water services.

For chlorine to be effective against microorganisms, it must be present in sufficient concentration, and must have adequate time to react. For continued protection against potentially harmful organisms in distribution systems or premise plumbing systems, some level of chlorine needs to be maintained after the initial application. The remaining chlorine is known as residual chlorine.

The efficacy of chlorination is affected by many factors, including chlorine concentration, contact time, pH, temperature, turbidity, buffering capacity of the water, concentration of organic matter, iron and the number and types of microorganisms in the water system (in biofilms and free-living). The anti-microbial efficacy of chlorine declines as pH increases >7, with significant loss of efficacy at pH >8. Free chlorine is degraded rapidly at elevated water temperatures, which is a concern for hot water chlorination.

Chlorine can react with organics, inorganics and non-halogens in the water to form DBPs. Some DBPs have been shown to cause cancer and reproductive effects in lab animals and may cause bladder cancer and reproductive effects in humans.

Continuous chlorination at high levels in premise plumbing systems can result in objectionable tastes and odors along with irritation of skin, eyes and mucous membranes. Continuous chlorination can contribute to corrosion with associated leaks in plumbing systems.


Monochloramine

The primary use of monochloramine in water systems is to maintain a disinfectant residual in the distribution system. Monochloramine has a more persistent and stable disinfectant residual than chlorine. It causes fewer unpleasant tastes and odors in drinking water than other disinfectants. Monochloramine has a much lower disinfection efficacy than free chlorine, and if used as a primary disinfectant, it requires a much longer contact time.

Monochloramine is effective for controlling bacterial regrowth and controlling biofilms due to its ability to penetrate the biofilm. Monochloramine and chlorine have different mechanisms of action; monochloramine is more specific, and chlorine reacts with a wider array of compounds. For equivalent chlorine concentrations, monochloramine was shown to initially penetrate biofilm 170 times faster than free chlorine.

Monochloramine can be formed by first adding chlorine then ammonia or vice versa. Often ammonia is added after chlorine has acted as a primary disinfectant for a period of time, and the resulting monochloramine is used as a residual disinfectant. Monochloramine has been used in the treatment of drinking water for nearly 100 years.

Potential water quality issues associated with monochloramine include corrosion, formation of DBPs (although much lower than with free chlorine) and nitrification. The use of monochloramine can cause corrosion of the pipes and materials used in water systems. Corrosion can occur in two forms, including pitting and a more uniform thinning of pipe surfaces. Chloramines can also attack rubber and plastic components in a water system — 43% of utilities surveyed experienced an increase in degradation of rubber materials after chloramine disinfection was implemented.

The normal dosage rate for monochloramine is between 1.0 and 4.0 mg/L. Case studies generally support maintaining a chloramine residual in the plumbing system in the range of 1 to 2 mg/L as an effective means for containing biofilm growth, minimizing Legionella colonization and preventing outbreaks. As such, plumbing system best practices, such as maintenance of appropriate pH, maintenance of chlorine-to-ammonia ratios, flushing and frequent monitoring to demonstrate residual maintenance on an ongoing basis are essential.


Chlorine dioxide

Chlorine dioxide is a water-soluble gas that can easily diffuse through cell membranes of microorganisms. Chlorine dioxide was first used as a disinfectant in the early 1900s at a spa in Belgium; its use in drinking water disinfection became more common in the 1950s.

Chlorine dioxide is usually generated on site from sodium chlorite solutions and one or more other chemical precursors (e.g., sodium hypochlorite, hydrochloric acid, sulfuric acid) or by an electrochemical oxidation process. Stock solutions produced on-site typically have a concentration of 500 mg/L. Chlorine dioxide gas cannot be compressed or stored commercially because it is explosive under pressure. Therefore, chlorine dioxide gas is never shipped. Water treatment chemicals must meet the appropriate ANSI/AWWA standards or NSF/ANSI Standard 60.

Chlorine dioxide is considered less corrosive than chlorine. Observed corrosion marks on mild and galvanized steel coupons installed in pipe loops for chlorine dioxide treatment were similar to corrosion effects for other disinfectants.

Dosage rate is an important design criterion for chlorine dioxide disinfection systems. Chlorine dioxide dosage rates of 0.4 to 0.7 mg/L were reported by systems experiencing successful treatment performance. The required disinfectant dosage rate is dependent on system-specific conditions including pipe material and condition, the water’s disinfectant demand, water temperature, the extent of biofilm on pipe surfaces, pipe diameter and length, complexity of the premise plumbing system, treatment goals (e.g., Legionella control) and the water turnover rate.

Maintaining a total chlorine dioxide residual of 0.1–0.5 mg/L at the tap is usually sufficient to control Legionella, although higher residuals may be necessary in a heavily colonized system. Some systems have established a treatment goal of maintaining a minimum chlorine dioxide residual of 0.3 mg/L at distal. If treatment with a residual higher than 0.8 mg/L is determined to be necessary, the facility should ensure that emergency disinfection procedures are developed and followed so that human consumption of a concentration of chlorine dioxide greater than the MRDL does not occur.

The location of disinfectant application point(s) is a critical design decision. The location may affect the required dosage rate and the time needed to inactivate Legionella. For example, if chlorine dioxide is added at the cold water service entry point to the building, the dosage rate should be sufficient to achieve an adequate disinfectant residual at hot water taps at distant points in the building. However, the need to comply with drinking water standards may drive a design decision to install multiple treatment units in the building’s plumbing system.


Copper silver ionization

Copper silver ionization systems typically consist of flow cells that contain metal bars or anodes (containing copper and silver metals) surrounding a central chamber through which water flows. A direct electric current is passed between these anodes, releasing the copper and silver ions into the water stream. The amount of ions released depends on the composition of the anode and is controlled by the electrical current applied to the bars and the water flow rate.

The use of silver ionization for water disinfection was developed by the National Aeronautics and Space Administration (NASA) for Apollo spacecraft drinking water and wastewater systems. The combined use of copper and silver ions for water treatment initially focused on the disinfection of swimming pools as an alternative to using high levels of chlorine.

CSI was first reported on the effective use of controlling Legionella in hospital water systems, specifically for L. pneumophila. CSI systems are currently used in buildings with complex water systems to control the growth and occurrence of Legionella bacteria. Studies have documented CSI applications controlling Legionella in hospitals worldwide.

The use of CSI may result in corrosion. Materials compatibility and water quality will dictate the severity of corrosion. Awareness of the types of materials and water chemistry in a premise plumbing system is critical to maintaining system integrity. Maintaining copper and silver at the levels recommended by the manufacturer is a best practice in achieving operation effectiveness. Note that monitoring typically includes measurement of the total metal concentration, which includes copper and silver that are bound up as complexes, as well as copper and silver ions. The presence of copper and silver ions is thought to be critical for treatment effectiveness, so maintaining proper pH and avoiding interfering materials is also important.

CSI systems can be plumbed into either the cold-water entry pipe or plumbed into the hot water line. Note that construction including new copper pipe can add copper to water for a time via leaching. Newly installed CSI systems generally require a period to adjust system output to achieve the desired level of metal ions. Representatives from the manufacturer are typically involved in on-site start-up and balancing of the system.

In the next article, we will introduce other tools for legionella control, such as ultraviolet light, superheat and flush and filtration.

KEYWORDS: engineers legionella mitigation legionella prevention plumbing engineers

Share This Story

Looking for a reprint of this article?
From high-res PDFs to custom plaques, order your copy today!

James dipping

James Dipping, PE, CPD, GPD, ARCSA AP, FASPE, Plumbing Engineering Discipline Lead for North America for Stantec, has more than 28 years of experience a plumbing engineer, and serves on the ASPE Legionella Design Guide Working Group, the IAPMO Hot Water Return Task Group, and the ASPE Thermal Disinfection Working Group.

Recommended Content

JOIN TODAY
to unlock your recommendations.

Already have an account? Sign In

  • Worker using the Milwaukee Tool SWITCH PACK drain cleaner

    Pipeline profits: Drain cleaning, pipe inspection create opportunities

    Drain cleaning and inspection services offer lucrative...
    Green Plumbing and Mechanical
    By: Nicole Krawcke
  • Uponor employee, Arturo Moreno

    The reinvestment in American manufacturing and training

    Plumbing & Mechanical Chief Editor Nicole Krawcke and...
    Plumbing News
    By: Nicole Krawcke and Natalie Forster
  • March 2024 Women in Plumbing hero image of woman engineer overlayed by circle of hexagon shapes with numbers from 1 to 10

    Celebrating 10 Influential Women in the Plumbing Industry

    Celebrating Women's History Month and Women in...
    Plumbing News
    By: Nicole Krawcke
Subscribe For Free!
  • eNewsletters
  • Online Registration
  • Subscription Customer Service
  • eMagazine
  • Manage My Preferences

IPEX celebrates grand opening of new Florida distribution center

IPEX celebrates grand opening of new Florida distribution center

AI can boost efficiency and profitability for plumbing, HVAC contractors

AI can boost efficiency and profitability for plumbing, HVAC contractors

Bell & Gossett Illustrates Path to Net-zero at AHR Expo

Bell & Gossett Illustrates Path to Net-zero at AHR Expo

NIBCO Press Solutions

NIBCO Press Solutions

More Videos

Sponsored Content

Sponsored Content is a special paid section where industry companies provide high quality, objective, non-commercial content around topics of interest to the Plumbing & Mechanical audience. All Sponsored Content is supplied by the advertising company and any opinions expressed in this article are those of the author and not necessarily reflect the views of Plumbing & Mechanical or its parent company, BNP Media. Interested in participating in our Sponsored Content section? Contact your local rep!

close
  • J.J. Keller CMV vehicles on road
    Sponsored byJ. J. Keller & Associates, Inc.

    The dash cam game-changer for small business safety

Popular Stories

Plumbing equpment parts and wrench on the white background close up.

Plumbing & Mechanical 2025 Plumbing Tools Survey

Six tankless water heaters that feed the nutraceutical manufacturer’s operations.

How to deliver large volumes of hot water quickly and intermittently

Latin American plumber fixing a toilet in the bathroom.

Troubleshooting common airflow plumbing issues

PM BEMIS June 25 Free Webinar: Optimizing Plumbing Solutions for Single-Family, Multi-Family & Public Spaces

Events

November 13, 2024

Future Proofing MEP: Navigating the 2026 High Efficiency Water Heating Standards

Join our deep dive into DOE’s new standards so you can future-proof your MEP practice.

EARN: 0.1 ASPE CEU; 1 AIA LU/HSW; 0.1 IACET CEU*; 1 PDH

View All Submit An Event

Poll

Will business be up or down in 2025?

Do you anticipate business in 2025 to be up or down in comparison to 2024?
View Results Poll Archive

Products

The Water Came To A Stop

The Water Came To A Stop

See More Products

Download the FREE Water Conservation, Quality & Safety eBook: Plumbing Trends Increasing Safe Water Availability

Related Articles

  • light filament

    James Dipping: Non-chemical water treatment options for Legionella control

    See More
  • faucet with running water

    James Dipping: Remediation tactics for Legionella outbreaks

    See More
  • Man using tablet with smart home control functions at home.

    Smart plumbing systems – a ways to go

    See More

Events

View AllSubmit An Event
  • November 13, 2024

    Future Proofing MEP: Navigating the 2026 High Efficiency Water Heating Standards

    Join our deep dive into DOE’s new standards so you can future-proof your MEP practice. EARN: 0.1 ASPE CEU; 1 AIA LU/HSW; 0.1 IACET CEU*; 1 PDH
View AllSubmit An Event
×

Keep your content unclogged with our newsletters!

Stay in the know on the latest plumbing & piping industry trends.

JOIN TODAY!
  • RESOURCES
    • Advertise
    • Contact Us
    • Directories
    • Store
    • Want More
    • Supply House Times
  • SIGN UP TODAY
    • Create Account
    • eMagazine
    • eNewsletter
    • Customer Service
    • Manage Preferences
  • SERVICES
    • Marketing Services
    • Reprints
    • Market Research
    • List Rental
    • Survey/Respondent Access
  • STAY CONNECTED
    • LinkedIn
    • Facebook
    • Instagram
    • YouTube
    • X (Twitter)
  • PRIVACY
    • PRIVACY POLICY
    • TERMS & CONDITIONS
    • DO NOT SELL MY PERSONAL INFORMATION
    • PRIVACY REQUEST
    • ACCESSIBILITY

Copyright ©2025. All Rights Reserved BNP Media.

Design, CMS, Hosting & Web Development :: ePublishing

search
cart
facebook instagram twitter linkedin youtube
  • Sign In
  • Create Account
  • Sign Out
  • My Account
  • NEWS
  • PRODUCTS
  • CONTRACTORS
    • BATH & KITCHEN PRO
    • BUSINESS MANAGEMENT
    • HIGH EFFICIENCY HOMES
    • TECHNOLOGY
    • WATER TREATMENT
    • PMC COLUMNS
      • Dave Yates: Contractor’s Corner
      • John Siegenthaler: Hydronics Workshop
      • Kenny Chapman: The Blue Collar Coach
      • Matt Michel: Service Plumbing Pros
      • Scott Secor: Heating Perceptions
  • ENGINEERS
    • CONTINUING EDUCATION
    • DECARBONIZATION | ELECTRIFICATION
    • FIRE PROTECTION
    • GEOTHERMAL | SOLAR THERMAL
    • PIPING | PLUMBING | PVF
    • PME COLUMNS
      • Christoph Lohr: Strategic Plumbing Insights
      • David Dexter: Plumbing Talking Points
      • James Dipping: Engineer Viewpoints
      • John Seigenthaler: Renewable Heating Design
      • Lowell Manalo: Plumbing Essentials
      • Misty Guard: Guard on Compliance
  • RADIANT & HYDRONICS
    • RADIANT COMFORT REPORT
    • THE GLITCH & THE FIX
  • INSIGHTS
    • CODES
    • GREEN PLUMBING & MECHANICAL
    • PROJECT PROFILES
    • COLUMNS
      • Codes Corner
      • Natalie Forster: Editorial Opinion
      • Guest Editorial
    • SPONSOR INSIGHTS
  • MEDIA
    • PODCASTS
    • VIDEOS
    • WEBINARS
  • RESOURCES
    • INDUSTRY CALENDAR
    • DIRECTORIES
    • EBOOKS
    • PM BOOKSTORE
    • CE CENTER
    • MARKET RESEARCH
    • CLASSIFIEDS
  • EMAGAZINE
    • EMAGAZINE
    • ARCHIVE ISSUES
    • CONTACT
    • ADVERTISE
    • PME EMAGAZINE ARCHIVES
  • SIGN UP!