The Case for Vacuum Sewers
There are more than 2.3 million inmates in America’s jails
and prisons. If they were all in one location, it would be
the 23rd largest city in America. Some correctional facilities
are, in fact, like small cities. For example, one of the largest
prisons in the United States is the Louisiana State Penitentiary
with more than 5,000 inmates.
Regardless of size, every jail and prison must deal with infrastructure and utilities.
They use water and create sewage that must be conveyed and treated. As a result,
maintenance and repairs are important cost items as well as sensitive environmental
When Clay County, Ind., began planning its new 170-bed jail in
2004, the architects and county officials had an opportunity to address some
of the unique infrastructure challenges that corrections officers face. Among
the most important was the sanitary sewer system.
Like the staff at most
correctional facilities, Clay County’s maintenance personnel spent an inordinate
amount of time dealing with clogged toilets at their old jail because insubordinate
inmates would frequently flush items down their toilets in order to clog the
pipes and create nasty backups.
“At our old facility, inmates would flush T-shirts, belt buckets, small plastic
cups and other items down the toilet,” says Clay County Sheriff Michael Heaton.
“We would have to have a plumber come in with an auger to remove the obstruction.
This created a security situation because we had to remove the inmate from his
cell, plus we had to shut off the plumbing for most of the building. It was a
huge waste of time and resources.”
Chief custodian Wayne Knox says it usually took more than an hour to unclog a
gravity sewer line.
“First you had to remove the prisoner, then you had to pull the stool out, get
an auger in there and remove the obstruction, and then replace everything,” Knox
says. “You really had your work cut out for you.”
Most of the problems caused by clogged toilets were eliminated when the design
team for the new jail chose modern vacuum sewer technology from Airvac Inc. Now,
when a clog occurs it can be cleared in minutes without entering the cell.
“Within the chase behind the cells, all the pipes and valves are exposed,” Knox
says. “If something does get caught in a vacuum valve, we know about it right
away because it continually pulls vacuum, which makes a noise. There also
is a call-out notification at the control panel. Every cell has a shut off valve,
so we simply shut off that cell and remove the obstruction. The whole process
takes about 10 minutes.”
The design of the new low-flow toilet stools and the
vacuum pressure within the system make it difficult for inmates to flush items
that can clog the line. Many of the larger items they used to flush won’t
fit through the smaller orifice of the toilet, and the smaller items are usually
sucked through the line at high velocity to a grinder that shreds them into small
bits. The effluent is then passed into a vacuum collection tank and later pumped
into the city’s municipal sewer main.
Dave Sholl, vice president of Schenkel Shultz Architecture in Fort Wayne, Ind.,
had no previous experience with vacuum sewers before designing the Clay County
“When researching the project, we found that the new Clay County Jail’s sewer
would tap into a sewer main that was already near capacity,” Sholl says. “The
existing sewer main would not be able to handle the additional effluent from
a traditional gravity sewer in the new jail.”
Sholl’s team looked for a system
that requires less water and discovered that vacuum sewers use much less water
than conventional gravity systems.
Water usage for a vacuum toilet can
be adjusted from approximately three to six pints per flush. Standard gravity
toilets use about 1.6 gallons of water per flush, so the jail is now using about
a gallon of water less per flush.
Multiply the amount of water saved by the number of toilet flushes per day and
the potential for significant savings is hard to ignore. The impact on the local
municipal wastewater system and treatment facility is also greatly reduced.
Vacuum sewer technology has been around for more than 40 years and is used
in cities across the country and around the world. Vacuum toilet collection
systems also can be found on all major cruise ships and airplanes.
heart of an Airvac vacuum system is the vacuum collection station. The
system arrives at the customer’s site completely assembled and prewired with
the only required electrical connection to be made at the control panel.
vacuum collection station contains all of the equipment necessary to generate
and maintain vacuum pressure within the vacuum piping system, empty the collection
tank when full, and provide all system alerts.
When a toilet is flushed, the pneumatic vacuum valve opens and sends the wastewater
into the vacuum piping where it is propelled at speeds of up to 18 feet per second
to the shredder. The wastewater then empties into a 650-gallon collection tank
where it is held until a sufficient volume has been collected. When that
predetermining level is reached, the wastewater is pumped into the city’s municipal
sewer line or to a wastewater reuse system.
In addition to using less water, the technology requires very little electrical
energy, is self-contained and is virtually odorless. Because operation of the
vacuum collection system is monitored by the control panel, leaks occurring anywhere
in the system can be easily identified and quickly isolated and repaired. Also,
leaks in a vacuum piping system are drawn into the piping, not pumped out of
the system, thereby eliminating drips and puddles of wastewater —problems that
often are found with conventional gravity wastewater systems.
Vacuum sewage collection uses smaller diameter piping compared to conventional
gravity piping, providing lower material costs and labor installation costs.
Unlike a conventional gravity flush toilet, the Airvac vacuum toilet not only
flushes down, but it can also can flush horizontally or even up to an overhead
This allows for flexibility in the design layout of new construction and expands
the possibilities for renovation or expansion projects. Piping also can be installed
independently of slopes, thereby allowing for flexibility in the routing of pipes
around stationary objects, such as air ducts, wall openings or other utilities
“Because it’s not a gravity system you don’t have to worry
about slopes,” Sholl says. “You can run PVC piping around columns or pipes. Because
we designed the vacuum system piping to be included in the chase behind the cells,
we didn’t have to worry about underground piping. That was a big help in expediting
the construction process.”
At Clay County Jail, the staff does a quick tour of
the chases each morning to inspect the vacuum and water lines and check the central
vacuum station where the shredder, collection tank and control panels are located.
The entire process takes only an hour, which generates a time savings and a reduction
in maintenance costs.
Jailers also like the convenience of vacuum sewers when there is a shakedown
in the facility. They can prevent inmates from flushing items down the toilet
by simply shutting a few valves, and they can isolate specific cells or blocks
without shutting off the sewers to the entire facility.
The unique characteristics of vacuum sewers help provide greater control of the
sewer system and therefore more control of the inmates.
“The overall cost savings along with ease of operation associated with vacuum
sewers make it easier to manage the facility, ” Heaton says.
This article appeared in the March/April 2010 issue of Correctional
News. If you would like to read the entire story as it appeared in the
magazine, you can download
a pdf, or you may request
to Special Themed Articles page.