Do High Efficiency Toilets Really Work?
By Bruce Martin
In an industry long considered stodgy and non-inventive, it is interesting that in the last half-century, the toilet has been one of the most technologically improved products produced in all of North America. Since the end of WWII, new flushing innovations — some good, some not so good — have emerged in each decade. Leading-edge WC’s consumption flush has been reduced by 80%. The industry’s latest innovation is called high efficiency toilets (HETs). HET means a water closet that uses at least 20% less or 1.28 gallons-per-flush [gpf] than the 1.6 gpf federal limit. While the term is impressive sounding, the question is whether this “innovation” is a step forward or backward.
Background
In the first two decades following WWII, toilet design focused on the toilet’s physical size. The siphon-jet and reverse-trap styles dominated. At that time, water was cheap and its availability was viewed as unlimited. Toilet designers had no interest in conservation. The most popular two-piece closet was gravity activated and consumed between 5-7 gpf. Some one-piece versions used as much as 10 gallons.
The 1970s brought severe droughts and shortages of waste-treatment capacity. Widespread construction moratoriums resulted. These started fundamentally changing the North American toilet market. Conservation started becoming important. One manufacturer imported a Swedish gravity- activated combination that used less than 1.6 gpf. However, its extraction capability was considered poor by most Americans and it never gained favor with the consumer.
One of the most significant water closet technological innovations of the 20th century was introduced in the mid-70s. Called a flushometer-tank (pressure-flushing device), it was designed as a retrofit product to replace the water storage tank on gravity two-piece WCs. When installed on a 51/2 gpf (gravity) bowl, flush consumption was reduced by more than 50% [e.g. 2.5 gpf]. The product failed primarily because of adaptability problems associated with the enormous variation in gravity bowl hydraulic designs and under capitalization of the manufacturer.
During the 1970s, water conservation started to become a national issue. Responding to severe shortages, many communities instituted user restrictions, including large increases in water and sewer rates and restrictions on use. Sensing a market opportunity, American Standard introduced the first 31/2 gpf toilet called “Watersaver.” As that product gained popularity, competitors followed by offering similar products — many using their same 51/2 gpf bowl but with a smaller storage [water saving] tank. Most of these toilets failed to meet consumer expectations. Americans strongly objected to double-flushes and/or bowl clogs. Because virtually all of the “problem” 31/2 gpf toilets had been certified as conforming to the American National Standard’s minimum performance requirements, ANSI received much of the blame.
A revision of the national standard was quickly completed, in which the watersaver [31/2 gpf] category was officially established along with “updated” performance requirements. This motivated many state legislatures, particularly in the West, to mandate these new low consumption toilets. While the new 31/2 gpf gravity WCs represented a step backward in performance — compared to the 51/2 types — they were, nevertheless, widely accepted because of the greater social good [water conservation].
In an effort to mitigate the impact of building moratoriums, the first hint of socialism hit the fixture industry in the early 1980s with the emergence of community-financed subsidy programs aimed at the replacement of high-volume toilets with the new watersaver types. These actions were eagerly endorsed by the FMs since they increased market demand.
In 1984, Mansfield introduced the Quantum™, the first pressure-assisted (PA) water closet combination designed specifically to hydraulically maximize the discharge characteristics of the flushometer-tank. This revolutionary six-liter combination, offered both superior extraction and drainline carry capability, equal to the old 51/2 gpf types. The Quantum’s performance unleashed a strong market demand for toilets that “worked.” Other fixture manufacturers quickly entered the market with their pressure-assisted versions. Sales of pressure-assisted WCs soared.
Despite the fact that fixture manufacturer sales of pressure-assisted WCs were growing rapidly in the early 90s, most vitreous china manufacturers were unenthusiastic about purchasing their flushometer tanks from an outside source. It lessened their value-added share of the product’s value. Since gravity WCs could be produced in-house for less cost than a PA version, virtually all domestic manufacturers developed and introduced 6-liter gravity-activated WCs tailored after European designs. States and municipalities quickly accepted them and, particularly in the western U.S., even started mandating them. The environmental movement got into the act by proposing federal maximum WC consumption legislation of six liters. Their efforts became law effective in 1994.
Again, it is almost universally recognized that those initial gravity-activated 6L toilets thrust on the market were unsatisfactory. Because of their considerably lower head pressure, it took bowl designers quite some time to learn the hydraulic principles necessary for the lower discharge volumes. Through the end of the decade, while 6L gravity-activated WC design gradually improved, the market shift from gravity- to pressure-assisted continued, aided by Eljer’s introduction of a new, 2nd-generation [quieter] pressure-flush technology.
Shortly after the turn of the century, Toto introduced the most significant innovation in gravity flush technology in the last 50 years — the enlarged flush valve flapper, 3" diameter up from the traditional 2". Because water is not compressible, the 125% larger inlet area allows a faster in-flow — gallons per minute (GPM) — into and through the bowl. A faster flow rate improves extraction capability and flush noise.
As knowledge of the improved performance of WCs with enlarged flappers spread, competitors quickly followed. Some manufacturers even superseded the 3" flapper with 4" flappers1. With the improved extraction, the reputation of 1.6 gpf gravity WCs began improving. As significant as these innovations were, they only slowed the market gains of pressure-assisted toilets, primarily because pressure-assisted WCs still had better extraction capability and consumed 32% less water [1.1 GPF].
High performance toilets
Gravity enthusiasts then countered with the introduction of a new performance designation called the “high-efficiency toilet” — applicable to any WC that uses 20% less than the federal maximum of 1.6 gpf [e.g. 1.28 gallons]. The term, “high efficiency toilet” is a clever marketing slogan since it suggests better flush performance than standard 1.6 GPF toilets. One has to ask: “Is the implication justified?”
To have any value, a lab test must relate to market performance. HETs are required to meet ANSI minimum performance requirements. This writer’s opinion is that the best laboratory method currently available for evaluating toilet performance is the MaP test procedure, which was jointly developed by Koeller Associates and Veritec Associates. MaP stands for “Maximum Performance of Toilet Fixtures.” Their 13th edition, published in November, 2008, reported the maximum bulk extraction capability for 736 gravity-fed water closet combinations.
The MaP test protocol consists of flushing a number of flexible latex sausages filled with a soybean paste. Each sausage weighs 50 grams. With the water supply set at 50 psi, the toilet is flushed five consecutive times with a load of 200 grams. If the test specimen is successfully extracted, the load is then increased to the next load level — 250g; 300g; 350g; 400MaP, etc. up to 1,000 grams — or until the WC fails to fully extract the test specimens’ more than one time out of five attempts.
MaP test cylinders
The following table shows that 40 standard single-flush units with 2" FVs averaged 551 [MaP] grams compared to 74 standard single-flush units with 3" FVs averaged 713 grams — 29% better.
Since history tells us that 1.6 gpf gravity WCs with 2" flush valves were generally unsatisfactory and that toilets with 3" flappers are at least marginally acceptable, 700 MaP grams looks like a responsible threshold of acceptable performance.
A 700 threshold suggests that currently available dual-flush, HET toilets may need some improvement2 and that most HETs, on average, probably require some double-flushing — thus higher water consumption. While single-flush HETs are better than dual-flush types, they still appear to be marginal. However, in fairness to HETs, it appears that hydraulic design is critical since:
- 59 of 288 [20%] gravity-activated high efficiency toilets obtained scores of 700 or higher — nine with 2" flush valves and 50 with 3" FV; and,
- 41 of 43 [95%] pressure-assisted HET water closets scored higher than the 700 threshold;
This suggests that consumers need performance information to be able to make intelligent purchasing decisions. All toilets are NOT created equal. n
Bruce Martin is the inventor/developer of the Flushmate® flush system, sold to Sloan Valve Co. in 1986, and the PF/2 Energizer® flush system sold to Geberit [Switzerland] in 2002. His latest invention is the FlushMuffler® noise suppression technology designed for pressure-assisted WCs.
(1) The 4" flush valve represented a 400% increase in inlet area over the traditional 2" size.
(2) Dual-flush HET water closets typically have two discharge volumes – 0.5 and 1.28 gallons. While the MaP data does not state at which flush setting their tests were conducted, it is reasonable to assume it was at 1.28 gpf.