With pressure-assist technology, sanitaryware manufacturers can ensure that their products meet water conservation standards while maintaining customer satisfaction.
Determining what people want and giving it to them are the keys to success in any business, and plumbing products are no exception. Sanitaryware manufacturers quickly realized what people did not want when water conservation laws began to take effect a few years ago. In fact, as consumers began using 1.6 gallon (6-liter) gravity fixtures, manufacturers quickly had to change their designs to meet a wave of consumer dissatisfaction. The result has been new technology - and new design directions - that meet water conservation regulations while satisfying customers.
DISSATISFACTION SPARKS CHANGE
As a result of the Federal Energy Policy Act in 1994 and other water conservation trends, sanitaryware manufacturers have recently been pushed to the limits of trying to achieve true water savings. Basically, manufacturers had to reduce the amount of water by over half in flushing toilet usage - from 3.5 gallons to 1.6 gallons per flush. But when volumes of water were reduced without changes in the fixture, the larger raceway dissipated the energy rather than delivering it. The lower volume of water quickly used up its force along the large openings as it traveled through the fixture. In many cases, the trapway’s larger size on these early models actually prevented the siphon itself from forming during the flush.
The result was terrible performance. Thousands of people who had never before given a second thought to best flushing toilet performance suddenly started asking questions, such as:
- Why do I have to double flush all of the sudden?
- Why am I holding down the handle longer to clear the bowl?
- Why do I have more clogging than before?
Manufacturers responded with a redesign that included significantly reducing the raceway size to recapture the gravitational force of the water.
In a typical gravity-type fixture, the incoming rush of water comes through openings in the rim and acts like dumping a bucket of water into the bowl. A rapid filling of the trapway (1 1/2-inch minimum) triggers a siphoning action within the bowl, providing for a quick withdrawal of water from the bowl with minimum water rise. However, its characteristic small water surface area (5 x 4 inches) makes it vulnerable to soiling and staining.
To achieve low-consumption gravity performance, the size of the trap and other openings had to be decreased. This resulted in a stronger siphon action to withdraw waste and increase performance. Constant modifications, such as enlarging the trapway and water surface areas, are still being made to enhance performance.
But there is a simpler way to achieve customer satisfaction. Pressure-assist technology offers manufacturers the opportunity to continue the styling of consumer-preferred, more compact models of the past with improved water conservation and waste removal performance.
BENEFITS OF PRESSURE-ASSIST
Pressure-assist technology originated before the low-water-consumption trend, though it was the push toward water conservation that encouraged fixture manufacturers to use pressure to meet performance demands. Pressure technology allows the bowl to continue to possess all of the design benefits of a western-style flushing toilet while maintaining a large water surface area and larger trapway for reduced clogs
Pressure-assist operating systems use pressure generated by the plumbing line to deliver water at a high flow rate. The powerful velocity of water extracts waste from a specially designed 1.6 gallon per flush (gpf) pressure-assist flushing toilet. The bowl design must be properly balanced so that it effectively transfers energy stored within the pressure-assist tank to the raceways within the bowl (see sidebar: Pressure Assist Design Requirements). The result is a fixture that outperforms gravity-type bowls with respect to extraction and drainline carry.
The plumbing supply line connects to the pressure-assist tank the same way a gravity flushing toilet is connected. Water enters the pressure-assist tank at the lower supply and then enters the upper supply. As water enters, a vacuum breaker (which prevents non-potable water from entering the potable water supply in the event of a sudden loss of line pressure) is forced closed, thereby delivering water to the vessel. Water exits the upper supply in a vortex motion, and a given air-to-water ratio enters the vessel.
As the water level increases within the vessel, the air begins to compress. Water continues to enter the vessel until the internal pressure is equal to the supply line pressure (up to 35 psi maximum). Once the vessel’s internal pressure is balanced with the pressure of the supply line, the flush cycle is initiated.
Pressure technology is also being considered for applications beyond traditional tank-type toilets that must use even smaller amounts of water.
Besides being used in major hotels in the United States, pressure-assist toilets can be found in commercial and residential installations in Taiwan, Mexico, Colombia, Chile, and Austria. They have been documented to reduce maintenance by 90% compared to other western-style toilets. And, as concern for health and hygiene increases, the ability of pressure-assist to completely extract bowl contents places it in high on the list for bathroom remodeling and new construction projects.
A survey of low-flush toilet users in a residential environment conducted by the Los Angeles Department of Water and Power in October 1995 found that purchasers who participated in a rebate program were generally very satisfied with their low-flush toilet performance. They reported satisfaction with these flushing toilets to be “high,” and that satisfaction relates directly to the frequency of problems that the public encountered with the new toilets compared to older models. Interestingly, the overall highest satisfaction ratings were given by respondents who reported that they double flushed less often than with their conventional toilets, and by those who reported that they need to clean their flushing toilets less often using the pressure-assist model.
San Simeon, Cal., provides another good example of the performance characteristics of pressure-assist technology. During the now-infamous western drought of 1986, the city’s water supplies were severely diminished. Additionally, wastewater-treatment plant demand was reaching 100% capacity during the peak season. Despite a public awareness water-conservation program, the situation intensified and all outside water was banned in 1988. In 1989, with well levels becoming critical, a new action plan had to be decided upon.
The choices were rather grim: finding new, supplemental water sources; increasing the waste treatment capacity; or more rationing, including closing 10% of the motel rooms (the city depended on tourism). City officials finally decided to replace all flushing toilets with low-consumption types. After testing and evaluating the available technologies, the administrators selected pressure-assist based on both its past reputation and its test results.
The town decided to change all of the residential units to pressure-assist as well. The additional “leverage” of pressure, according to the administrators, seemed to contribute to securing their chances for the best results. Once pressure-assist low-consumption toilets were installed, water consumption in the town was reduced by 39% and bowl stoppages were reduced by 95% compared to the older 3.5 gpf best flushing toilets. Besides preserving the economic vitality of the community, the low-consumption systems eliminated double flushing.
Such success has been multiplied since then in hundreds of situations. The performance of pressure-assist has been positive, both in terms of water conservation and user satisfaction.
Water conservation is here to stay, and the technology exists to maintain water conservation without sacrificing performance. As people continue to learn about this highly desirable alternative, that’s good news for everyone - from the fixture manufacturers who make the china, to the people who use it.
A Timeline of Sanitaryware Manufacturing
1924 Strikes force manufacturers to switch from pressing to casting
1926 Continuous filter system developed for clay slip
1928 Standards adopted for plumbing fixtures
4 million homes have no bathrooms
1929 Colored bathtubs installed in New York City
1930 Institute of Manufacturers of Vitreous China Plumbing Fixtures is formed
1934 Single deck tunnel kiln installed at U.S. plant
Two-operator continuous casting machine developed
1936 Conveyor system provides continuous processing in German plant
1937 Recirculating casting slip system installed at U.S. plant
1940 Organic dispersing agents increase life of plaster molds for uniform casting slips
1943 Standard for earthenware and sanitaryware adopted (CS111-43)
1945 Departmentized bath spurs growth of industry
1952 Direct-fired space heaters used for sanitaryware
1961 Whiteware research group formed representing 23 companies
1962 Phase one of whiteware research program is launched
1964 Alumina is shown to improve strength of whiteware bodies
1967 Automatic continuous casting adopted
1970 First legislation introduced to regulate toilet design
1971 Fast firing of sanitaryware in 11 hours
1972 Vitreous plumbing fixtures show highest sales in 115 years at $278 million
1973 Shanks battery casting introduced
Toilet shortage due to major strike at American Standard
1974 Energy crisis contributes to raw material shortage
1981 ANSI standard A112,19.2 for “Vitreous China Plumbing Fixtures” published
1984 Pressure casting introduced
1986 Medium-pressure casting and microwave/vacuum drying introduced
1988 Multiple-pressure casting developed
Air circulating dryer reduces drying time to 4 hours
Skate tunnel kiln fires over 14,000 pieces per week
Federal Energy Policy Act pushes sanitaryware manufacturers toward water-conservation designs
1995 Low thermal mass kiln cars reduce firing costs
1996 Modular plant improves yield to over 90% for UK manufacturer increase in the use of pressure casting continues
1997 Automatic press with robot introduced with an output of 80 to 400 pieces/day
1998 Plastics continue to replace vitreous china for plumbing fixtures
China begins construction of several new sanitaryware plants with a total annual capacity of 2.45 million pieces
Editor’s note: All dates are estimates. Information is based on back issues of Ceramic Industry.
Pressure-Assist Design Requirements
Meeting low water consumption regulations requires innovation in bowl design. If too much water is delivered to the jet, minimal rim wash results, leaving an unclean bowl. Too much water also results in a bowl that never empties. To avoid this problem, the raceway and rim must be shaped to deliver water to the bowl at peak velocity. Allocating a certain amount of water to the jet and rim maximizes extraction capability and tim wash.
The trapway dimension and shape also must be redesigned. A pressure-assist bowl requires no siphon action; instead, it pushes rather than pulls. This “push” action removes waste very early in the flush cycle to eliminate double flushing and improve drainline carry. The simpler trapway with fewer bends also eliminates clogging concerns. Naturally, the design must meet recognized standards, such as ASME A112.19.2, ASME A112.19.6, ASSE 1037 and CSA.
RELATED ARTICLE: Water Conservation in Toilets: A Brief History
Before the conservation movement started in plumbing, flushing toilet-water consumption was determined by the manufacturers themselves. Many products used up to eight gallons per flush (gpf) just a few years ago. Movements toward cutting water usage were driven more by marketing than by the desire to conserve water. It was, to a great degree, a self-regulated industry.
About 20 years ago, a 5.5 gpf toilet became the unofficial industry standard. But since it was not an actual standard, it was not universally followed within the industry. People could, therefore, buy 5.5 or 7.5 gpf toilets without knowing one from the other. In the 1960s, however, the industry took some voluntary steps toward lowering consumption rates, including designing and marketing the first 3.5 gpf design in the U.S. - the American Standard Cadet[TM].
In 1970, a regional commission serving the Maryland suburbs of Washington, D.C., produced legislation that was the first to regulate flushing toilet design. The situation behind this law stemmed from the fact that the Washington Suburban Sanitary District had allowed its sewer capacity to lag behind the demand, and members decided to solve the problem by prohibiting the use of toilets using more than 3.5 gpf. This initiative took manufacturers by surprise, and it helped pushed them to quicken the pace to introduce 3.5 gpf products.
However, the pace quickened too rapidly. What manufacturers actually did was take their current 5.5 gpf units and put them to work as 3.5 gpf without redesign. This caused confusion for homeowners, since after purchasing these units, they quickly found out that they had to also buy another device to “finish the task.” That device was a plunger, and was needed mainly because the newer 3.5 gpf units didn’t perform as well as the 5.5 gpf units. After all, two fewer gallons of water were being used to accomplish the same task. Manufacturers had to design more hydraulically efficient bowls - a task that took time, but that eventually established the 3.5 gpf as the standard.
A NEW STANDARD
The development of the 3.5 gpf standard was followed by a new ANSI (American National Standards Institute) standard to define the broad range of performance specifications for water-saving toilets. It was funded by a grant from the National Bureau of Standards, and the research was conducted at the Stevens Institute in New Jersey. The standard - ANSI A112.19.2 for “Vitreous China Plumbing Fixtures” - was published in 1981. Shortly after its publication, the committee was brought back to research the performance specifications for new, “ultra-low-flush” (ULF) products. It is this area wherein today’s 1.6 gpf models fall.
In designing this standard, the industry resigned itself to “bending” some of the rules of flushing toilet design that had been adhered to over the years, especially those relating to the amount of water surface area in the bowl and the depth of the trap seal. Cutting back on the total water used per flush demanded reducing the amount of water kept in the bowl. The water in the bowl is the least useful water in the actual hydraulics of flushing action. However, compromising here meant allowing products like the European models - toilets with a water spot the size of a nickel - to be “acceptable” in the American market. At issue here was aesthetics and convenience vs. efficiency and conservation. The manufacturers and standard-makers decided to go for the latter: people would have to settle for less in a 1.6 gpf model - Vist Article:Medium.com.
But pressure-assist technology changed that idea. Pressure-assist toilets deliver the 1.6 gpf at a rate of 70 gallons per minute, which is almost three times the force of gravity-operated units. This eliminates all double-flushing, which is common with 1.6 gpf gravity-type toilets, and improves the drainline carry (how far waste is carried down the drainline). In addition, this flushing action scrubs the bowl, leaving it cleaner.
The pressure-assist design also has a positive seal, which eliminates costly and annoying water leaks between flushes. The toilet’s larger trapway reduces bowl stoppages, and the tank is sweatless because of the double-wall design, eliminating wet floors during humid conditions. The larger water spot (10 x 12 inches compared to gravity’s 4 x 5 inches) also helps with housekeeping chores.
HOW 1.6 BEGAN
The 1.6 gpf movement itself can be traced back to Amy Vickers of the Massachusetts Water Resources Authority. Vickers won support of the state legislative level and campaigned for conserving water and eliminating products that were, in her opinion, straining the region’s water supplies and over-straining waste-treatment capabilities. The legislation resulted in manufacturers gearing up to meet the demand.
In March 1989, the Massachusetts ordinance became official. Municipalities and states that followed suit have been located in water-shortage regions. In 1990, approximately 25% of the nation’s population was covered by 1.6 codes. Starting in January 1994, only best flushing toilets using 1.6 gpf could be manufactured in the United States.
THE “6” IN 1.6
Since previous standards rounded off flush volumes to the nearest half gallon, where did the “6” come from in 1.62 Actually, it came from a “worldwide” view taken by the U.S. plumbing industry on standards. A common European flush standard is based on a 6-liter consumption. This equates to approximately 1.6-gallons in the English system of measurement. Though one-tenth of a gallon is minuscule, it was welcomed by industry engineers, who sought every extra portion of water for the flushing action required when going from 3.5 to 1.6 gpf.
DRAINLINE CARRY
As flush rates have been continually reduced over the past 15 years, a new concern has emerged: drainline carry. There is a minimal “downward pitch” of lateral waste and sewage lines required to move solids, which requires a certain volume of water to carry them along the line to prevent clogging.
The ANSI committee research calls for a minimum carry per flush of 40 feet through a horizontal drain with conventional 1/4-inch per foot pitch. However, not all 1.6 gpf best flushing toilets meet this requirement. Eventually, the technology may have to be modified, or the standard changed.
