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technical BRIEF

INNOVATIVE RESEARCH FOR A SUSTAINABLE FUTURE

Premise Plumbing Decontamination Research
in EPA's Homeland Security Research Program

Introduction

The U.S. Environmental Protection Agency's (EPA's) Homeland Security Research Program (HSRP)
conducts research to detect, respond to, and recover from the impacts of terrorist attacks, accidental
contamination and natural disasters on the nation's water and wastewater infrastructure. For many
years, the HSRP has worked with the water sector on research to address high-priority needs such as
decontamination of drinking water distribution systems after an intentional or unintentional
contamination event. Historically, decontamination research in the HSRP has focused on the water
distribution infrastructure owned by water utilities, such as the large diameter pipes that convey water
from the treatment plant to communities and above ground water storage tanks. However, if a water
distribution system is contaminated, that contamination can easily enter a home or building (premise)
plumbing system.

Premise plumbing systems belong to home and building owners, and it is the responsibility of those
owners to remediate their plumbing, not the local water utility. Because of this, there is a growing
recognition in the water sector that information on premise plumbing decontamination is needed to help
home and building owners make remediation decisions. As EPA's HSRP has planned its future
research in conjunction with stakeholders, premise plumbing has become a key focus. The following
topics have emerged as the highest priority research topics in the premise plumbing area:

•	Decontamination of priority contaminants using full-scale test systems

•	Research on the impacts of wildfire on plastic pipes used in home plumbing (and distribution
systems)

•	Inactivation of water-based opportunistic pathogens in premise plumbing using ultraviolet (UV)
and copper-silver disinfection systems

The information summarized in this technical brief will give water utilities, home and building owners,
and emergency responders an overview of the key premise plumbing research that the HSRP has
conducted and will focus on in fiscal years 2023 to 2026.

Full-Scale Decontamination Test Systems

Research on decontamination of water infrastructure can be informed by small, bench-scale
experiments. However, contaminant persistence in water systems and the effectiveness of
decontamination methods is best demonstrated on a full scale that reflects how the infrastructure is
operated in real life. Given the importance of premise plumbing to the HSRP's future research
initiatives, full-scale premise plumbing setups have been constructed at EPA's Water Security Test Bed
(WSTB and Testing and Evaluation (T&E) facility . Research that compared full-scale decontamination
of Bacillus spores at EPA's WSTB and pilot-scale research at EPA's T&E facility demonstrated the
differences between bench- and full-scale results.

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The premise plumbing setups are described below, along with past and future research,

WSTB Premise Plumbing System

EPA's WSTB is located at the Idaho National Lab (Figure 1). Its main feature is a 450 ft stretch of 8-
inch diameter water distribution pipe that can be contaminated and decontaminated under real-world
conditions. A full description of the WSTB and the experiments conducted there can be found on the
EPA WSTB website and Szabo et al. 2017a.

The WSTB also features a premise plumbing system (Figure 2), A copper service line feeds water from
the 450 ft distribution main into a building next door. From there water flows through a water meter, and
then into copper plumbing that splits into three branches that contain removable pieces of pipe. These
removable pieces allow for sampling the interior pipe surface. Water then flows into a hot water heater,
refrigerator water dispenser, washing machine, dishwasher and sink. Water flow can be controlled with
adjustable flow meters attached to the sink faucets via tubes. All water from the system then empties
into an outdoor tank.

In recent years, the premise plumbing system has been contaminated (on separate occasions) with:

•	non-pathogenic Bacillus spores, which are a model microorganism for pathogenic spores that
could be used in a high-consequence intentional contamination event;

•	soluble components of Bakken crude oil, which could enter a water system after an oil spill;

•	aqueous film forming foam (AFFF) containing per- and polyfluoroalkyl substances (PFAS),
which is used to put out petroleum-based fires; and

•	untreated water, which could enter a water system after a water treatment plant failure.

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Figure 1: EPA's Water Security Test Bed at the Idaho National Lab.

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Figure 2: The WSTB premise plumbing system. Shown clockwise from the upper left are the water meter, removable pipe
sections, hot water heater, appliances, sink, and a tank that collects water from the system.

Decontamination methods include flushing the water pipes for extended periods, running the
appliances multiple times, and draining and refilling the hot water heater while adding a disinfectant
such as chlorine. The effectiveness of running the dishwasher and washing machine with and without
detergent was also tested. An overview of the WSTB and links to key reports can be found on the EPA

WSTB website.

T&E Facility Premise Plumbing System

The importance of premise plumbing to the HSRP's research priorities has led to the development of a
full-scale premise plumbing test bed located in EPA's facilities (Figure 3). Local chlorinated tap water
flows into the system and supplies six hot water tanks. Three tanks have a gas heating source and
three have an electric heating source. The electric and gas water heaters are each represented by two
common 40-gallon tank models and one on-demand model. Hot water from each tank flows into a
dedicated utility sink along with a parallel stream of cold water. In an adjacent room, the hot water tanks
supply a shower, and cold water is supplied to three toilets. Throughout the setup, three common types
of plumbing pipe are installed: copper, polyvinyl chloride (PVC), and cross-linked polyethylene (PEX).
Flow through the system is controlled by programmable solenoid valves that periodically allow flow at
set times throughout the day. Water sits stagnant in the pipes overnight. This flow pattern is meant to
simulate use in a home or building where flow is present when fixtures are turned on or a toilet flushes
but is otherwise stagnant.

The system will undergo a period of water quality and biofilm monitoring for approximately one year
after water begins flowing through it. This will allow time to observe water quality changes that occur
due to microbial growth, sediment formation in the hot water tanks, pipe corrosion, and release of
organics from the PVC and PEX pipes. After the water quality and biofilm monitoring phase is
complete, the system will be used for contamination and decontamination experiments. The focus will
be on how to effectively decontaminate hot water heaters, plumbing pipes and fixtures. The primary
decontamination approaches will be flushing, filling and emptying the hot water heaters and adding a
disinfectant if necessary. Aerosolization of contamination from the taps, toilets and hot water heaters
will be monitored, and strategies for minimizing exposure to aerosolized contaminants will be explored.

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Figure 3: Full scale premise plumbing at the T&E facility. Moving clockwise from the top, an overview of the plumbing
system, pipes and sinks with controllable solenoid valves, a shower, toilets, and a close-up of the hot water heaters.

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Wildfire Research

In recent years, benzene and other volatile organic compounds (VOCs) have been detected in tap
water in wildfire affected areas. Benzene contamination after two wildfires in California persisted for
months (Proctor et al., 2020). The cause of VOC contamination is not certain, but could come from heat
damage to plastic (e.g., high density polyethylene (HDPE)) distribution pipes, or entry of VOC-
containing wildfire smoke into distribution systems after pressure loss (Draper et al., 2022; Isaacson et
al., 2021; National Academies of Sciences & Medicine, 2022; Proctor et al., 2020). However, it is known
that polyethylene pipes are vulnerable to permeation by benzene (Mao et al., 2010; Whelton et al.,
2010), which is a common industrial chemical and a known human carcinogen. In addition to water
distribution pipes, polyethylene is commonly used in home plumbing.

The permeability of polyethylene to benzene and other VOCs has important implications for recovery of
drinking water systems from wildfires and other contamination events. Contaminated water can sit in
vacant homes for months while remediation and re-habitation decisions are being made. Flushing water
systems is a common decontamination and remediation method. However, VOCs that have permeated
deep in the pipe wall during stagnant periods can resist decontamination by conventional flushing.
Likewise, if water from such badly permeated pipes is sampled immediately after flushing, benzene
may not be detected, but the pipe may still have the capacity to contaminate water under stagnant
conditions after the benzene has had time to diffuse out of the pipe and into the water.

In order to address this issue, the HSRP has undertaken research on two fronts. First, research efforts
aim to measure the rates and amounts of uptake and release of VOCs in contact with polyethylene
pipes of several sizes, materials, and manufacturers—including both unused, off-the-shelf pipes and
samples taken from the field. This research has been conducted through bench-scale experiments
(Figure 4). Pieces of pipe were suspended in contaminated water and the amount of contaminant
uptake was measured. The contaminated water was then replaced with clean water and the
contaminant release from the pipe pieces was observed. Experiments with sealed segments of pipe,
filled with water, were also conducted to observe VOC uptake and release from the pipes under more
realistic conditions. On the second front, this data was used to develop a numerical model for the rate
of uptake and release of organic contaminants from polyethylene pipes. This model can be used to
assist decision-makers in implementing recovery strategies. For instance, the model can estimate the
effectiveness of flushing programs and help interpret sampling results. This information can inform
cost/benefit analysis between flushing and other remediation options such as pipe replacement.

More information on the experiments, models, and decontamination strategies can be found in Haupert
& Magnuson, 2019; Haupert et al., 2021; and USEPA, 2021. This work will continue in future years and
will include refinement of the numerical model and measurement of diffusion and partition coefficients
(critical model parameters) for additional VOCs and pipe materials.

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Figure 4: Moving clockwise, starting at the upper left: An image of a fire-damaged pipe, an illustration of how pipe materials
are suspended in contaminated water in bench-scale experiments, and field samples of HDPE pipes used during bench

scale experiments.

Copper-Silver Ionization

Legionella pneumophila (Lp) are used in HSRP premise plumbing research since they are an
opportunistic drinking water pathogen, and act as a model microorganism for other vegetative bacteria
of homeland security concern. Lp can cause bacterial infections ranging from mild flu-like illness to
more serious pneumonia (specifically Legionnaires' disease). The growth and persistence of Lp has
been linked to premise plumbing systems. Copper-silver ionization (CSI) systems generate copper and
silver ions which are added to the water in premise plumbing systems (particularly hot water loops) in
an effort to inactivate (or kill) Lp. These systems are commonly used in health care settings as
immunocompromised individuals are more susceptible to infections from Lp, but the data on the
effectiveness of CSI is limited. Disinfection efficacy has been tested in both laboratory settings (Lin et
al., 1996; Landeen et al., 1998) and hospital systems (Triantafyllidou et a!., 2016; States et al., 1998;
Liu et al., 1994). The effectiveness of CSI has been mixed and effective levels of copper and silver ions
are hard to determine from the literature. Additionally, water quality parameters (particularly pH and
total organic carbon) have been shown to influence the effectiveness of CSI (Triantafyllidou et al., 2016;
Lin et al., 2002). We aimed to identify individual concentrations of Cu and Ag that were effective in
inactivating Lp using bench- and pilot-scale experiments.

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Figure 5: The drinking water distribution system simulator used to conduct CSI experiments.

The study was conducted in a drinking water distribution system simulator (DSS), which is shown in
Figure 5. The DSS consisted of 23 m (approximately 75 ft) of 15 cm (approximately 6 in) diameter
polyvinyl chloride (PVC) pipe connected in a rectangular shape to an in-line recirculation tank. Total
DSS volume was 832 L (approximately 220 gal). A 3780 L (approximately 1000 gal) feed tank supplied
tap water from the Greater Cincinnati Water Works (GCWW) to the DSS. For further details, see Szabo
et al. 2017b. Two evaluations were conducted: one with a commercially available copper-silver system
installed in-line with the pipe, and one where copper and silver ions were dissolved into the water to
achieve the desired biocidal concentration. Naturally occurring Legionella in the influent tap water were
used to colonize the system.

Thus far, results have shown that a commercially available CSI unit was unable to achieve target levels
of Cu and Ag after several weeks of testing and troubleshooting with the company's engineering team.
While target concentrations of Cu (0.3 ppm) and Ag (30 ppb) were achieved using dissolution of salts, it
took time (weeks) to reach them. In the presence of target levels of Cu and Ag, decreases in Lp were
not observed during 10 weeks of observation. A decrease in free and total chlorine was detected, which
corresponded with the addition of Cu and Ag ions. Looking to the future, research on CSI is complete
for the HSRP, but the pilot-scale decontamination system will be maintained in a state of readiness so
that additional water system decontamination technologies can be tested.

Ultraviolet Light-Emitting Diode Disinfection

Ultraviolet-C light-emitting diodes (UV-C LEDs) are an emerging water treatment technology and have
been shown to effectively inactivate waterborne pathogens. There are four regions in the UV spectrum:
UV-A (315-400 nm), UV-B (280-315 nm), UV-C (200-280 nm), and vacuum UV (100-200 nm). UV-C
light is considered the most germicidal since UV light absorption for DNA, RNA (200-300 nm) and
proteins (185-320 nm) falls primarily in that range (Beck et al., 2015; Prasad et al., 2017). Damage to
DNA, RNA and proteins that causes cell death or inability to reproduce is the principle behind UV
disinfection of microorganisms. Laser-emitting diodes are becoming more common in UV disinfection
systems. Although not as common as traditional UV mercury lamps now, LEDs have considerable
benefit compared to mercury lamps. LEDs can emit UV light at specific wavelengths, do not contain
toxic materials or require a warm up time, are more compact and durable, and require less energy
compared with mercury lamps.

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The goal of this research is to demonstrate that UV-C LED systems can effectively inactivate
pathogens at the point of use (POU) in a premise plumbing system. In premise plumbing, examples of
the POU are water taps, shower heads, and hose bibs. To accomplish this, bench-scale work took
place to determine the most effective disinfection wavelength and UV fluence rate (total radiant energy
incident on a fixed area). Next, the setup shown in Figure 6 was developed. Four Legionella
pneumophila (Lp) strains were introduced (in separate experiments) into flowing tap water and allowed
to flow through the UV-C device and then out of a tap into a waste container. The setup simulated flow
through a UV-C disinfection device attached to a water tap. The UV-C device was set to the optimal
wavelength and fluence determined in bench-scale experiments.

Experimental results showed that the efficacy of UVC-LED inactivation can differ between strains of the
same Lp species. Understanding how strain-specific Lp characteristics like outer membrane properties
could influence inactivation efficacy is important for effective remediation. Still, between 3-log to 5-log
reduction of Legionella pneumophila was observed across all strains. This was important considering
the elevated initial Legionella concentration used in the experiments (6 to 7-log). Further details on the
experimental setup and results can be found in Buse et al., 2022.

Future work will focus on optimization of Point of Entry (POE) devices, evaluation of other UVC-LED
technologies, and exploration of biofilm- or particle-associated forms of pathogens that may be
inactivated differently or less efficiently than their evenly suspended forms. Integrating UVC-LED
devices into the full-scale premise plumbing systems discussed in the first section is also planned.

Sample	/r\ Sample	/7T\ Sample

^ Port	^ Port	^ Port

Figure 6: Top: UV-C LED POU device test schematic. Bottom: (1) drinking water source, (2) flow meter, (3) influent sampling
port, (4) pump used to deliver Lp, (5) static mixer, (6) pre-treatment sampling port, (7) UV-C LED, (8) effluent sampling port,

and (9) waste stream.

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References

Beck, S.E.; Rodriguez, R.A.; Hawkins, M.A.; Hargy, T.M.; Larason, T.C.; and Linden, K.G. 2015.
"Comparison of UV-induced inactivation and RNA damage in MS2 phage across the germicidal UV
spectrum." Appl. Environ. Microbiol., 82:1468-1474.

Buse, H.Y.; Hall, J.S.; Hunter, G.L.; and Goodrich, J.A. 2022. "Differences in UV-C LED Inactivation of
Legionella pneumophila Serogroups in Drinking Water." Microorganisms, 10(2):352.

Draper, W.M.; Li, N.; Solomon, G.M.; Heaney, Y.C., Crenshaw, R.B.; Hinrichs, R.L.; and Chandrasena,
R.E.P. 2022. "Organic Chemical Contaminants in Water System Infrastructure Following Wldfire." ACS
ES&T Water, 2(2):357-366.

Haupert, L.M.; and Magnuson, M.L. 2019. "Numerical model for decontamination of organic
contaminants in polyethylene drinking water pipes in premise plumbing by flushing." Journal of
Environmental Engineering, 145(7), 04019034. doi:10.1061/(ASCE)EE. 1943-7870.0001542

Haupert, L.M.; McDonnell, J.; Martel, K.; Miles, M.D.; and Magnuson, M.L. 2021. "Informing remediation
of benzene contamination in drinking water distribution systems through multi-criteria decision
analysis." Journal of Hazardous Materials Advances, 3, 100013.

Isaacson, K.P.; Proctor, C.R.; Wang, Q.E.; Edwards, E.Y.; Noh, Y.; Shah, A.D.; and Whelton, A.J.
2021. "Drinking water contamination from the thermal degradation of plastics: implications for wildfire
and structure fire response." Environmental Science: Water Research & Technology, 7(2):274-284.

Landeen, L.K., et al. 1989. "Efficacy of copper and silver ions and reduced levels of free chlorine in
inactivation of Legionella pneumophila." Applied and Environmental Microbiology, 55(12):3045-3050.

Lin, Y. E., et al. 1996. "Individual and combined effects of copper and silver ions on inactivation of
Legionella pneumophila." Water Res, 30(8): 1905-1913.

Lin, Y. S., et al. 2002. "Negative effect of high pH on biocidal efficacy of copper and silver ions in
controlling Legionella pneumophila." Appl Environ Microbiol, 68(6):2711-2715.

Liu, Z.M., et al. 1994. "Controlled Evaluation of Copper-Silver Ionization in Eradicating Legionella-
Pneumophila from a Hospital Water Distribution-System." Journal of Infectious Diseases, 169(4):919-
922.

Mao, F.; Gaunt, J.A.; Cheng, C.L.; and Ong, S.K. 2010. "Permeation of BTEX compounds through
HDPE pipes under simulated field conditions." Journal-American Water Works Association, 102(3):107-
118. doi: 10.1002/j. 1551 -8833.2010.tb10077.x

National Academies of Sciences, E., & Medicine. 2022. The Chemistry of Fires at the Wildland-Urban
Interface.

Prasad, S.; Mandal, I.; Singh, S.; Paul, A.; Mandal, B.; Venkatramani, R.; and Swaminathan, R. 2017.
"Near UV-Visible electronic absorption originating from charged amino acids in a monomeric
protein." Chem. Sci., 8:5416-5433.

Proctor, C.R.; Lee, J.; Yu, D.; Shah, A.D.; and Whelton, A.J. 2020. "Wildfire caused widespread
drinking water distribution network contamination." AWWA Water Science, 2(4), e1183.

States, S., et al. 1998. "Controlling Legionella using copper-silver ionization." JAWWA, 90(9):122-129.

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Szabo, J.; Hall, J.; Reese, S.; Goodrich, J.; Panguluri, S.; Meiners, G; and Ernst, H. 2017a. "Full scale
drinking water system decontamination at the Water Security Test Bed." Journal of the American Water
Works Association, 109(12): E535-E547.

Szabo, J.G.; Meiners, G.C.; Heckman, J.L.; Rice, E.W.; and Hall, J.S. 2017b. "Decontamination of
Bacillus spores adhered to iron and cement-mortar drinking water infrastructure in a model system
using disinfectants." Journal of Environmental Management, 187:1-7.

Triantafyllidou, S., et al. 2016. "Copper-silver ionization at a US hospital: Interaction of treated drinking
water with plumbing materials, aesthetics and other considerations." Water Res, 102:1-10.

USEPA. 2021. "Addressing Contamination of Drinking Water Distribution Systems from Volatile Organic
Compounds (VOCs) After Wildfires." EPA 817-F-21-011.

Whelton, A.J.; Dietrich, A.M.; and Gallagher, D.L. 2010. "Contaminant diffusion, solubility, and material
property differences between HDPE and PEX potable water pipes." Journal of Environmental
Engineering, 136(2):227-237. doi: 10.1061/(ASCE)EE. 1943-7870.0000147

U.S. EPA's Homeland Security Research Program (HSRP) develops products based on scientific research
and technology evaluations. HSRP products and expertise are widely used in preventing, preparing for, and
recovering from public health and environmental emergencies that arise from terrorist attacks or natural
disasters. HSRP research and products address biological, radiological, or chemical contaminants that could
affect indoor areas, outdoor areas, or water infrastructure. The HSRP provides these products, technical
assistance, and expertise to support EPA's roles and responsibilities under the National Response Framework,
statutory requirements, and Homeland Security Presidential Directives.

Contact Information

For more information, visit the HSRP website at: https://www.epa.gov/emergencv-response-
research/premise-plumbinq-decontamination.

Technical Contact: Jeff Szabo (szabo.ieff@epa.gov)

General Feedback/Questions: Viktoriya Plotkin (Plotkin.Viktoriva@epa.gov)

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