&EPA

United States
Environmental Protection
Agency

Distribution System Water Quality

Protecting Water Quality with Pigging and Swabbing

Pigging and swabbing can be used to remove biofilm, scale, and accumulated sediment from water mains. These maintenance
practices help to reduce microbial contamination risks, decrease chlorine demand and disinfection byproduct levels, address
customer complaints, and increase distribution system flow. Compared to flushing, pigging and swabbing use less water, remove
more sediment, and more aggressively remove biofilm. Pigs and swabs typically enter the water main under the force of water
from a fire hydrant or another supply source, and then they are pushed along by water from the distribution system. This fact
sheet is part of EPA's Distribution System Toolbox developed to summarize best management practices that public water systems
(PWSs), particularly small systems, can use to maintain distribution system water quality and protect public health.

Conventional Pigging and its Use for Pipe Cleaning

•	Conventional pigging is a technique used to mechanically scrape hard scale
(corrosion tubercles), biofilm, soft scale, and loose deposits from pipes with a
hard body, conical-shaped mechanical cleaning device made of foam, steel, or
plastic. Pigs are forced through a water main by water pressure.

o Bare pigs made of high-density foam may be launched first to

determine the inside diameter of the pipe and find any obstructions,
o Cleaning pigs have a special coating to help remove scale or biofilm.
o Scraping pigs are equipped with wire brushes or scrapers to remove
corrosion tubercles.

•	Pigs can sometimes get stuck in more complex piping configurations.

•	If pigging is used to scrape corrosion tubercles from unlined cast iron pipe, the
pipe surface should be protected prior to putting back into service.

Ice Pigging and its Use for Pipe Cleaning

•	Ice pigging involves using a slurry of crushed ice and salt in the flushing water
to scrape pipe surfaces clean.

•	Compared to flushing, ice pigging uses less water and removes more
sediment. It generates higher shear rates along pipe surfaces than flushing and
is more effective in removing biofilm and accumulated manganese coatings.

•	The ice slurry can navigate obstructions more easily than swabs or other pigs.

Swabbing and its Use for Pipe Cleaning

•	Swabs are simple polyurethane foam plugs that are larger than the inside
diameter of the pipe and forced through the pipe by water pressure. Swabs
are generally less aggressive than hard body pigs and can navigate some
bends, tees, and diameter changes

•	Swabs can remove biofilm, soft scale, and loose sediment and do not require a
high velocity water flow. They can be used to clean new or repaired water
mains but not to remove corrosion tubercles.

•	Compared to flushing, swabbing uses less water and removes more sediment
and biofilm. It is also more effective in removing sticky manganese deposits.

•	Swabs can be purchased in various grades from soft to hard depending on the
cleaning objective (type of deposits) and the water main age and diameter.

Disclaimer: To the extent this document mentions or discusses statutory or regulatory authority, it does so for
information purposes only. It does not substitute for those statutes or regulations, and readers should consult the
statutes or regulations themselves to learn what they require. The mention of trade names for commercial products
does not represent or imply the approval of EPA.

Examples of Utility Actions

A PWS serving about 500,000
people in the midwestern U.S. was
unable to find a commercially
available tool for improving water
main cleaning effectiveness suitable
to their needs. In 2014, the PWS
developed a swabbing tool made of
4-inch-thick low-density foam that
could be dipped into a dilute
chlorine solution, inserted into the
pipe, and pushed and pulled to
scrub pipe surfaces to remove dirt
and contaminants and coat surfaces
with a bleach residue. The PWS
decided to use it during all water
main repairs.

A PWS serving 420 people in the
southeastern U.S. received
customer complaints about
discolored water and was not able
to conduct regular flushing due to
limited finished water storage
capacity. The PWS used ice pigging
to remove 350 pounds of sediment
from 18,000 ft. of 6-inch diameter
PVC water mains. The PWS found
that ice pigging used one-third as
much water as regular flushing,
improved water quality, and
reduced customer complaints to
near zero.


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Table 1: Resources and Guidelines for Pigging and Swabbing

Resource Title and URL

Relevance to Pigging and Swabbing

Miller et al., 2019. Ice Pigging Creates Clean Mains and Water
Quality Insights. Onflow, www.awwa.org.

Note: There may be a fee associated with obtaining this resource.

Describes ice pigging technology. Explains how
to collect and analyze sediments removed
from the pipe. Includes a case study.

Brandhuber et al., 2015. Legacy of Manganese Accumulation in
Water Systems. Denver, Colo.: Water Research Foundation.

www.waterrf.org

Friedman et al., 2016. Metals Accumulation and Release within
the Distribution System: Evaluation and Mitigation. Water
Research Foundation, Denver, CO. www.waterrf.org

Note: There may be fees associated with obtaining these resources.

Summarizes literature and presents utility
survey findings and case studies on using
swabbing and ice pigging for removing
manganese deposits from water mains.
Swabbing and ice pigging are more effective
than flushing in removing manganese
deposits. Includes utility guidance and a
framework for assessing manganese deposits.

World Health Organization (WHO). 2004. Safe Piped Water,
Managing Microbial Water Quality in Piped Distribution Systems.

https://www.who.int/

Describes swabbing techniques, including
advantages and limitations.

Ellison, D. 2003. Investigation of Pipe Cleaning Methods. Denver,
Colo.: Water Research Foundation, www.waterrf.org

Note: There may be a fee associated with obtaining this resource.

Discusses pipe cleaning applications for
pigging and swabbing. Describes costs,
expected results, and methods for handling
discharges.

Office of Water (4606)
EPA 815-F-22-010
August 2023


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