Tneme-News
High-Velocity Jet Cleaning Aids
Sewer Pipe Inspection
According to the U.S. Environmental Protection Agency
(EPA), the nation’s sanitary sewer collection systems have
a total replacement value estimated at $1 to $2 trillion.
“Effective and continuous management, operation, and
maintenance, as well as ensuring adequate capacity and
rehabilitation when necessary, are critical to maintaining
collection system capacity and performance while extending
the life of the system,” the EPA reported.
Sewer inspection is an important component of any
maintenance program, the EPA reported in its Guide
for Evaluating Capacity, Management, Operation, and
Maintenance (CMOM) Programs at Sanitary Sewer Collection
Systems. The EPA emphasized that, “Sewer system cleaning
should always be considered before inspection is performed
in order to provide adequate clearance and inspection
results.”
“The purpose of sewer cleaning is to remove accumulated
material from the sewer,” the EPA explained. “Cleaning helps
to prevent blockages and is also used to prepare the sewer for
inspections. Stoppages in gravity sewers are usually caused
by a structural defect, poor design, poor construction, an
accumulation of material in the pipe (especially grease), or
root intrusion. Protruding traps (lateral sewer connections
incorrectly installed so that they protrude into the main
sewer) may catch debris which then causes a further buildup
of solids that eventually block the sewer. If the flow is less
than 1.0 to 1.4 feet per second, grit and solids can accumulate
leading to a potential blockage.”
Accumulated material is commonly removed by hydraulic
methods such as high-velocity jet sewer cleaning (also
known as hydrocleaning). Only when the pipe is sufficiently
cleaned can it be visually inspected.
Tnemec has tested several high-velocity jet nozzles commonly
used for hydrocleaning steel and ductile iron sewer pipes
lined with Series 431 Perma-Shield PL, a 100-percent solids
ceramic epoxy lining specifically designed for wastewater
immersion and fume environments. “Series 431 PermaShield PL further facilitates visual inspection methods (e.g.,
lamping, camera and Closed Circuit Television) because of
its reflective light green color,” according to, Vaughn O’Dea,
director of sales for Water & Wastewater Treatment. “The
color, ‘Sewer Pipe Green,’ allows trouble areas to be much
more apparent than they would be in pipe lined with a
black coating.”
Continued on back.
Cleaning crews are also advised to use smooth sewer hoses
and hose couplings in order to facilitate movement across
the pipe joints without creating damage to the lining and to
avoid using root cutters, saws or chain scraper nozzles.
In addition, O’Dea urged jetter operators and cleaning crews
to follow the Jetter Code of Practice manual published
by the National Association of Sewer Service Companies
(NASSCO). The manual offers a quick reference to safe use
of jetting machines, nozzles, hoses and other equipment
used in sewer cleaning operations.
The testing found Series 431 to be compatible with various
jetting nozzles (0-degree tips) commonly used for hydraulic
jet cleaning. “Municipalities using Series 431-lined ductile
iron or steel pipe can confidently employ today’s highvelocity jet cleaning equipment using the recommended
cleaning tools,” O’Dea noted.
The testing led to several guidelines outlined by Tnemec,
such as using cleaning nozzle assemblies with non-abrasive
wheels or skids positioned to prevent the assembly from
contacting the pipe lining. Other recommendations included:
• Limiting water pressure at the jet nozzles to 2,500
pounds per square inch (psi) and a maximum of 80
gallons per minute (302 LPM);
• Keeping cleaning nozzles a minimum of two inches (50
mm) standoff from the pipe surface;
• Maintaining fixed jet nozzles at no greater than a
30-degree angle of incidence to the pipe wall and
rotational or spinner nozzles at no more than a 90-degree
angle of incidence.
• Keeping the nozzle assembly moving continually, and
ensuring that 30-degree nozzles remain stationary no
longer than 60 seconds.
Accurate recordkeeping is also encouraged so that the
collection system’s owner or operator can create a database
with information on those areas prone to blockages so that
preventive maintenance and cleaning can be scheduled.
For example, in areas where there are restaurants, sewers
may need to be cleaned every six months to prevent grease
blockages.
“By routinely cleaning and inspecting their sewer systems
with modern methods, municipalities can better support
and maintain their vital infrastructure and ensure its
sustainability,” O’Dea added. “Pipes that are free of buildup
and coated with a reflective light green color will allow for
a more effective inspection.”
Originally included in May 2011 E-News.
Tnemec Company Incorporated 6800 Corporate Drive Kansas Cit y, Missouri 64120 - 1372 1 - 800 - Tnemec1 Fax: 1-816- 483-3969 w w w.t nemec.com
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