Vacuum toilets Provide Solutions in Correctional Facilities
With a responsibility to represent the taxpayer-owner, architectural and engineering consultants are hired to design a facility, which will usually be bid at the lowest cost, while still maintaining the necessary minimum standards. With correctional facilities, the highest costs are associated with the need to provide security. Capital costs, combined with operating costs, are compared, evaluated, and scrutinized in all areas. Several levels of planning, budgeting and value-engineering processes occur. One of the goals is to identify areas that will provide the “biggest bang for our buck.”
Vacuum TechnologyNew designs, tailored to meet strict correctional needs, have evolved with the introduction of vacuum technology. Although vacuum toilet systems have been around for many years in the transportation, marine and aviation industries, the technology is now being used for land-based projects, particularly correctional facilities. Why vacuum? Quite simply, it is a matter of cost and savings. To understand more fully the cost-saving implications, it is helpful to recognize some basics about vacuum technology.
A vacuum toilet system is an engineered system which uses vacuum to transport waste from plumbing fixtures—including toilets, sinks and showers—through a piping network to a central vacuum collection module. The vacuum collection modules usually consist of large storage tanks, vacuum pumps, sewage grinders and sewage ejector pumps. A programmed control panel interfaces all of the components and ties them together.
The piping network is usually specified with PVC-DWV plastic pipe and fittings. This allows for smooth transition of waste through the piping system. While gravity waste drain pipe sizes are typically 3 and 4 inches, vacuum systems allow the piping to be downsized to 2- and 3-inch lines. In addition, while gravity waste lines require a pronounced slope, vacuum piping requires a slope of only 1/16-inch per foot.
Because the flow of waste is vacuum assisted, “reform pockets” are used to help push the sewage through the piping. These pockets assist in pushing sewage along between flushes. During each flush, air is admitted into the piping, which then helps propel the sewage toward the vacuum central module. These reform pockets provide the flexibility to even out the piping over long runs.
Another area of savings is the elimination of fixture venting. Because vacuum piping does not require venting, less pipe is used. P-traps are also eliminated. Perhaps the biggest savings and cost factor is created by the low-volume vacuum toilets, which use 1/2-gallon (2 liters) of water per flush. Some studies show that inmates have a tendency to flush a toilet many times per day. Sgt. Mel Ballard, Salt Lake County Sheriff’s Department, Salt Lake City, Utah, notes, “On average, inmates will flush a toilet between 15 to 20 times a day.” Because water usage with vacuum toilets is one-third that of a conventional gravity system, incoming water costs and outgoing sewage treatment costs are considerably lower. As a result, studies show a significant payback in cost savings over the life of the facility.
Other advantages of a vacuum toilet system are inherent to the design. Owners and maintenance personnel often become frustrated with inmates who frequently abuse the plumbing system. Typically, an inmate uses a toilet as a garbage receptacle, which, not surprisingly, can cause all kinds of headaches for facility maintenance staff. When gravity plumbing systems are clogged, it commonly occurs down the line somewhere. Who’s the culprit? Which inmate created the problem? It’s often difficult to determine.
With a vacuum system, however, the problem usually occurs right at the fixture due to the design of the toilet and stays there for easy identification of the culprit. It is not uncommon to find inmates attempting to flush bed sheets, socks, shirts, paper products, and just about anything else imaginable. If flushed items do make it through the toilet openings, they usually are propelled through the piping system, through the grinders, and then stored in the vacuum central module until discharged to the treatment plant or sewer main.
How a Vacuum System WorksWhile we have mentioned the advantages of a vacuum plumbing system, how does it actually work?
- Toilets. When the flush button for the toilet is pressed, the discharge valve opens, allowing atmospheric pressure to force sewage through the piping to the vacuum tank. At the same time, the water valve injects water to rinse the toilet bowl. The discharge valve then closes so the water valve can reestablish the pool of water in the bowl.
- Lavatory and Sinks. Waste flows by gravity to an interface valve. The interface valve then opens and allows the waste to enter the vacuum piping.
- Shower and Floor Drains. Waste is collected in an accumulator area and, when filled, a pressure sensor triggers an actuator to open a valve and allows the waste to move into the vacuum piping.
- Vacuum Collection Module. The vacuum collection module features a control system that automatically regulates the operation of the vacuum and sewage ejector pumps. The vacuum pump creates vacuum in the system by pumping air from the vacuum tank and piping. Once a predetermined level of sewage is reached in the vacuum tank, the sewage is automatically pumped out by sewage ejector pumps to a treatment plant or sewer main.
The toilet flush control panel is unique and should be highlighted. Each toilet comes standard with a flush control panel. This includes a discharge valve, a timing control valve (which regulates the length of time to flush) and a water valve. These items are mounted on a panel, which is then attached to a wall inside a plumbing chase. Control is enhanced because the discharge valve also acts as a positive isolation valve, eliminating communication or the passing of contraband between cells. No electrical power or connections are needed to operate the toilet.
Further control can be achieved with an electronically controlled valve system. This type of control limits an inmate’s ability to abuse the system. For example, the toilet can be programmed allowing the inmate only one or two flushes per hour, with lockout times available. This gives facility management more control, rather than reacting to what an inmate might do to abuse the system.
Several Large InstallationsThere are many correctional facilities around the United States that use vacuum toilet systems. The first such project to use vacuum toilets was the Ventura County Jail, in Ventura, California. A total of 477 vacuum toilets were used in a two-story, campus-style project. The system has been in operation for over three years. The decision to use the vacuum system was reached after an extensive study was performed. According to Peter Roy, Project Manager for CRSS Constructors, “We put this vacuum system through its paces, interviewed current users, and performed tests at the factory before the project team was ready to recommend its use to the (Ventura County) Sheriff’s Department. In addition, the county saved $172,800 in initial construction costs.”
Shortly thereafter, in Youngstown, Ohio, the Mahoning County Justice Center was built with 490 vacuum toilets, using a high-rise (eight-story) building design. The design team on that project also conducted an extensive feasibility study of the system before making a decision. Bill Forteman, P.E., Project Engineer for M.S. Consultants, said, “Mahoning County required M.S. Consultants to design both a vacuum and gravity system to be bid by the plumbing contractors. The total plumbing cost with a vacuum system was $1,849,000 with an add-on of $236,000 for a gravity system. Additionally, with the cost of water at $6.49 per 1000 cubic feet and a sanitary cost of $6.20 per 100 cubic feet in 1992, the 1/2-gallon per flush vacuum toilet was estimated to save $108,000 per year.”
A new project, the Salt Lake County Adult Detention Complex, Salt Lake City, Utah, is a two-story campus style design scheduled to open in the Fall of 1999. It will contain over 1200 vacuum toilets, with an additional 1000 for future expansion, making this job the largest vacuum toilet project to date. Chief Deputy Sheriff Dan Ipson, Project Director, for the Salt Lake County Sheriff’s Department Construction Team, said, “We wanted to build the most modern, up-to-date facility in the country. We spent a considerable amount of time looking at various jail designs and concepts and decided that what we wanted wasn’t out there. We started from scratch, right from the ground up. We visited several facilities, got several ideas and then designed our own jail.”
After learning about the features and benefits of a vacuum toilet system, Ipson’s interest began to grow. Studies indicated significant savings in operational costs. Installation costs also showed savings. However, the deciding factor was the water savings. Considering the expected lifetime of the facility, “the savings on water is enormous,” Ipson notes.
An International PresenceInternationally, the vacuum toilet system is also making a presence. In Queensland, Australia, the Woodford Correctional Center was built using 480 vacuum toilets in a two-story, campus-style design. According to Bob Buman, AVAC–Australia, “The primary factors that convinced the government of Australia to consider a vacuum system were the reduction of in-line blockages and the security advantages. The water conservation was a bonus.” He indicated that they have their own water treatment plant on site.
One of the challenges faced in the design and commissioning of the system was the number of showers that had to be designed around. “Our maximum security cells are quite different from America,” Buman says, “in that each cell has its own shower, and they must be 24-hour accessible.” That translates to 500 showers on the Woodford project. Vacuum, again, showed significant savings in water costs and control, which were the primary factors that influenced the decision to use vacuum.
Vacuum Retrofit SystemsTo this point, discussion has centered on new construction projects. However, vacuum systems also lend themselves to remodel or retrofit applications. The system provides flexibility since a vacuum toilet can flush horizontally or upward, (20-foot maximum) as well as underground. This introduces many possibilities and ideas, whereas gravity is much more restrictive.
With new technology becoming more of a demand in the design of jails and prisons, manufacturers continue to develop products and systems that make them stand apart. New products, such as prison plumbing fixtures, which are designed to prevent suicide attempts by inmates, are becoming more important to the owners and operators of such facilities. Innovation and new product and system designs continue to prod us along in looking at alternative ways to do things better and more economically.