• 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
  • PRODUCTS
  • FEATURED PRODUCTS
  • 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
  • EBOOKS
  • PODCASTS
  • VIDEOS
  • WEBINARS
  • RESOURCES
  • INDUSTRY CALENDAR
  • DIRECTORIES
  • 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
    • FEATURED 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
    • EBOOKS
    • PODCASTS
    • VIDEOS
    • WEBINARS
  • RESOURCES
    • INDUSTRY CALENDAR
    • DIRECTORIES
    • 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: Non-chemical water treatment options for Legionella control

Specialty components to further reduce the risk of Legionella — part two.

By James Dipping
light filament

Victor Borisov/iStock/Getty Images Plus via Getty Images.

March 6, 2023

In my January column, I began a series focused on chemical and non-chemical additives or technologies that I treat as “must consider” for plumbing engineers in their design practices to reduce the risk of legionella bacteria developing in the domestic water system.

As I mentioned, these topics might not be a code minimum requirement, but as an engineering community, we have a responsibility to uphold the health and safety of the public. Therefore, we should be discussing these technologies for many different building types we come across in our design.

I’ll reiterate that as we consider these tools in our design, engineers must understand that the Environmental Protection 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;
  • Facility owners or operators who are considering adding treatment to their building’s premise plumbing system may wish to consult with their water supplier 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.

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 their document. As plumbing engineers, we cannot pretend to be experts in chemistry, which makes becoming 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 of NON-chemical water treatment options…

Ultra-violet light disinfection

UV disinfection is a well-established treatment technology for inactivating pathogens present in the environment. In the drinking water context, UV disinfection was initially most widely used in Europe, with hundreds of installations in place by 1985. In North America, UV disinfection has been more widely employed in drinking water applications since 2000 to address health concerns associated with Cryptosporidium. As of the spring of 2008, there were at least 300 PWSs in the United States and Canada with UV installations treating flows 350 gallons per minute.


UV is only effective at inactivating Legionella in the water that flows through the UV reactor. For existing facilities with Legionella present in the piping systems downstream of a UV reactor, supplemental controls such as thermal treatment or chemical disinfection will be necessary


UV reactor validation is used to define the operational conditions under which the pathogens of concern are inactivated for a specific UV reactor manufacturer and model. Validation is a method of determining the operating conditions under which a UV reactor delivers a specified dose. This generally involves initial tests using a surrogate organism (e.g., bacteriophage MS2) rather than the target pathogen (e.g., Cryptosporidium) to establish the dose relationship between the two organisms. The conditions that are examined for full-scale testing to establish dose are flow rate, UV transmittance (UVT) (a measure of the fraction of incident light transmitted through a material) and lamp output. EPA has developed guidance for validation of UV reactors.

There are several important lessons from installations of UV disinfection in hospital settings and

UV installations in general:

UV disinfection can be effective at controlling Legionella in facility piping. In the case of one new facility, a UV disinfection unit was installed on the incoming water supply, and none of the 930 cultures of hospital water were positive. In addition, there were no confirmed hospital-acquired Legionella infections over a 13-year study period;

UV is only effective at inactivating Legionella in the water that flows through the UV reactor. For existing facilities with Legionella present in the piping systems downstream of a UV reactor, supplemental controls such as thermal treatment or chemical disinfection will be necessary; and

UV reactors need to be maintained to remain effective. The quartz sleeves that house the reactors can be fouled by iron, manganese, calcium carbonate or other deposits that decrease UV output. Lamps and other reactor components also need to be replaced periodically to maintain treatment effectiveness. Fouling of the UV lamps was found to decrease effectiveness of the UV treatment. Liu et al. (1995) added filters to prevent scaling on UV lamps installed near the point of use in a hospital’s cold and hot water systems. After treatment with superheat/flush and shock chlorination, and installation of filters to remove particles that foul the UV lamps, the UV intensity of the lamps remained at 100 percent throughout the experiment and the showers remained Legionella-free for a period of three months.

UV disinfection does not produce a disinfectant residual. However, when UV disinfection is applied to waters containing a chemical disinfectant residual, the residual may be diminished following treatment with UV. Therefore, water treated using only UV disinfection may, in some cases, be susceptible to contamination at downstream points. More than one type of disinfection or other control measures should be strongly considered to protect the treated water downstream of UV disinfection.

Design considerations: Excessive turbidity and certain dissolved species inhibit the effectiveness of UV disinfection. Light transmission through water is impaired by particulates. Control valves and reducers should be avoided within five pipe diameters upstream of the UV reactor. Pipe expansion measures should also be avoided for at least ten pipe diameters upstream of the reactor to avoid jetting and swirling flow through the UV reactor. Redundancy or other measures should be built in to allow a UV reactor to be taken out of service for cleaning, lamp replacement and other maintenance. Valves to isolate UV reactors are recommended. In some cases, such as when UV reactors are flooded with cleaning chemicals, special valve arrangements may be beneficial on the outlet and inlet piping for flushing.

Ozone

Ozone is used in drinking water treatment for disinfection and oxidation. It is generated on-site as a gas using either air or liquid oxygen and is then dissolved into the water. When dissolved in water, molecular ozone (O3) is unstable and decomposes to hydroxyl radical, which is a stronger and typically more reactive oxidizing agent than molecular ozone.

The use of ozone in drinking water treatment is widespread throughout the world. As an oxidant, ozone can be used to oxidize iron, manganese, taste and odor compounds, and DBP precursors. It can oxidize organic matter into smaller molecules that are more easily biodegradable. As a primary disinfectant, ozone is more effective than chlorine, chloramines, and chlorine dioxide for inactivation of Cryptosporidium, Giardia and viruses. However, ozone cannot be used as a secondary disinfectant because it decays very rapidly and cannot maintain a residual in a domestic water distribution system.

I have decided that I’ll reserve the superheat and flush techniques for the next article, where I will organize this in a series of emergency remediation tactics used if a legionella outbreak is identified.

KEYWORDS: Legionella legionella control legionella prevention ozone disinfection ultraviolet light UV disinfection

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...
    Plumbing News
    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
Manage My Account
  • 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

NIBCO Press Solutions

NIBCO Press Solutions

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

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

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

Bath & Kitchen Pro 2025 Cover 900x550 hero image

eBook | Fifth annual Bath & Kitchen Pro

Integrate a heat pump with a boiler mounted on a brick wall.

How to integrate a heat pump with a boiler for dual temperature hydronic heating and cooling

Plumber using the DEWALT 20V MAX* Plastic Tubing Cutter to cut a white tube.

Making tough jobs easier: Most-used tools by plumbers in 2025

Nominations for Plumbing & Mechanical's NextGen ALL-Stars are now open. Submit your nomination TODAY!

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

2025 Bath & Kitchen Pro eBook

Related Articles

  • Specialty components

    James Dipping: Chemical and non-chemical additives 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

Related Products

See More Products
  • M:\General Shared\__AEC Store Katie Z\AEC Store\Images\Plumbing\new sites\pumping-away.gif

    Pumping Away and other really cool piping options for hydronic systems

  • alternative water sources.jpg

    Alternative Water Sources and Wastewater Management

  • the water book.jpeg

    The Water Came To A Stop

See More Products

Events

View AllSubmit An Event
  • August 26, 2014

    Free Webinar: Low Temperature Heat Emitter Options in Hydronic Systems

    With proper design, you can create systems that require supply water temperatures no higher than 120° F under design load conditions.
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
    • FEATURED 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
    • EBOOKS
    • PODCASTS
    • VIDEOS
    • WEBINARS
  • RESOURCES
    • INDUSTRY CALENDAR
    • DIRECTORIES
    • PM BOOKSTORE
    • CE CENTER
    • MARKET RESEARCH
    • CLASSIFIEDS
  • EMAGAZINE
    • EMAGAZINE
    • ARCHIVE ISSUES
    • CONTACT
    • ADVERTISE
    • PME EMAGAZINE ARCHIVES
  • SIGN UP!