Low-Flow Update, continued
Pumps and compressed air.
Kohler offers another approach to power-assisted flushing with
its Power Lite toilets (Figure 5). Instead of relying on vacuum
or water pressure, these high-end models contain a small
submersible pump that forces water from the tank to the bowl.
The manufacturer claims that the resulting flush is comparable
to that of a pressure-assisted fixture without the associated
noise; the obvious limitation is the need for a GFCI-protected
outlet within easy reach of the fixture. The Power Lite models
also offer the user a choice of two flush volumes -- a standard
1.6- or a water-saving 1.1-gallon flush for liquid waste. A
model with an electrically heated seat is also available.
Figure 5.Kohler's Power Lite series of toilets
contain compact submersible pumps that are said to produce a
flush similar to that of a pressure-assisted fixture. A
GFCI-protected outlet is required to supply power to the
Where the ultimate low-flow fixture is required, a California
company called Microphor offers several toilets that provide an
efficient flush on a mere 2 quarts of water (Figure 6). There's
a significant catch, though: In addition to the usual
water-supply-and-drain system, the Microphors need an external
supply of compressed air at 60 psi.
Figure 6.Microphor makes two residential toilets
that use a mere 2 quarts per flush. While the need for a
separate source of compressed air makes this impractical for
most applications, it's a useful option where local water
restrictions or a low-yield well rule out conventional low-flow
In a residential installation, that usually involves
installing a hardware-store air compressor in the basement or
garage and running a 3/8-inch copper line to the fixture,
according to Microphor spokesperson Walt Hess. Hess claims that
the air-assisted toilets are being used successfully in the
California communities of Carmel and Monterey, where severe
water restrictions are in effect, as well as in houses
elsewhere that are served by low-yield private wells.
Considering Peak Flow
A key difference between pressure- and vacuum-assisted toilets
and most gravity fixtures concerns something called peak flow
-- the maximum rate at which water passes through the trapway
of a given fixture during the flush cycle. Generally speaking,
pressure-assisted units have the highest peak flows.
According to Frank Vullo, director of product management for
Eljer, the company's pressure-assisted models have peak flows
approaching 95 gallons per minute. (Because the entire flush
consumes only 1.6 gallons, of course, that high rate of flow is
sustained for only a fraction of a second.)
Toto claims that its 3-inch flush valve offers a rate of flow
in the area of 50 gallons per minute, which Fernando Fernandez
describes as "up there with pressure-assisted toilets." The
average gravity fixture, he claims, tops out at about 30
The exact figures may be open to question, but it's evident
that the Totos and the pressure-assisted units do provide a
characteristically rapid flush: Push the handle, and the
contents of the bowl are sucked into the drain almost
instantly, with little or no visible swirling action.
That sort of high-speed flush may mean fewer clogs, but
manufacturers of gravity toilets based on the traditional
2-inch flush valve tend to downplay its value.
"They're all about forceful, and we're all about a sustained
flush," says Kohler engineer Kathryn Streeby. Kohler's gravity
fixtures, she contends, are designed to provide a relatively
gradual flush that swirls water vigorously around the bowl
during the drain cycle. According to Streeby, that still clears
bulky waste effectively while also reducing streaking and
leaving the bowl cleaner.
All toilets sold in the U.S. are required to meet ASME
standard A112.119.2M, which measures water-exchange and
bowl-cleaning performance as well as the ability to flush
several types of test media (Figure 7). But the fact that a
given fixture passes the ASME tests doesn't necessarily mean
that it will perform satisfactorily in the field.
Figure 7.To meet the minimum ASME performance
standard, a toilet must successfully flush 100 3/4-inch
polypropylene balls (top left) and a quantity of polyethylene
granules (top right). A dye test (bottom left) and an ink-line
test (bottom right) measure the fixture's ability to refill the
bowl with clean water and pass enough water through the holes
in the rim to minimize "skid marks."
"ASME is an absolute minimum," says Nick Quattro, director of
marketing for Briggs Plumbing Products. "If you don't set the
bar higher than that, you'll have a lot of unhappy
Individual manufacturers conduct extensive in-house product
testing, but the results are seldom made public in any
meaningful way. Performance tests undertaken by consumer groups
and public agencies, however, permit some worthwhile (though
inconclusive) product-to-product comparisons.
Independent testing. A
recent study by the NAHB Research Center is a good case in
point. Under contract with two West Coast utilities -- Seattle
Public Utilities and the Oakland, Calif., East Bay Municipal
Utility District -- the NAHB researchers subjected 49 current
models of popular toilets from 17 different manufacturers to a
variety of laboratory tests. Among other things, the
researchers evaluated flushing performance, flush volume, trap
diameter, and water-spot area.
But the most controversial part of the report was what the
researchers termed the "flush performance index" for each
toilet, based on the average amount of test media remaining in
the bowl after a series of test flushes. The scores for
individual toilets ranged from a perfect score of 0 --
indicating no material remaining -- to a high of 82. (To
establish a benchmark for what might be considered
unsatisfactory performance in the field, the NAHB researchers
also tested three used "problem toilets" that had been the
subject of user complaints; these were found to have flush
performance numbers ranging from 32 to 44.)
Of the 49 toilets evaluated by the NAHB researchers, 35 were
found to have flush performance indexes of ten or under, which
the report synopsis describes as a "reasonable criteria for
selecting the better performing toilets." Taken at face value,
those figures suggest that nearly a third of the fixtures on
the market don't work very well.
Conflicting studies. The
complete report, published on the NAHBRC website in October
2002, caused a furor in the plumbing industry. Manufacturers
whose products were found to perform well looked for ways to
use that information in their marketing efforts, while others
sought to downplay the results.
"I don't want to knock the folks at the NAHB," says Peter
DeMarco, "but I have a problem with any test that tries to rate
performance using just one type of media. The type of media you
choose can determine the results you get." Moreover, DeMarco
claims, the NAHBRC test loadings, consisting of various
combinations of floating and sinking sponges, were
unrealistically heavy. "They were over the top," he says. "They
were far above what a toilet would ever encounter in normal
Coincidentally, another independent evaluation of low-flow
toilets appeared in the October 2002 issue of Consumer
Reports magazine, about the same time as the NAHBRC report.
A side-by-side comparison of the two suggests that critics like
DeMarco have a point when they argue that different types of
objective tests can yield different results.
Of the NAHB's ten best-performing fixtures, for example, the
first nine were gravity models. One pressure-assisted toilet,
the Gerber Ultra, appeared in tenth place. The Consumer Reports
researchers, on the other hand, awarded their top eight spots
to pressure- or vacuum-assisted fixtures, with two gravity
models appearing in the ninth and tenth positions. The Toto
Ultramax, which tied for first place with another Toto fixture
in the NAHBRC rankings, ranked behind 20 of the 28 toilets
evaluated by the Consumer Reports staff.
Researcher Bob Hill, who led the NAHBRC team, believes that
the differences between the studies stem partly from the
different test media and loading rates used, and partly from
the fact that the Consumer Reports staff considered
factors like bowl-washing ability, draining, bowl dilution, and
noise in calculating an overall rating for each toilet.
"We looked at flushing ability, water-spot area, and flush
volume," Hill says, "but didn't try to come up with a weighted
average. Our intent was to put the raw data out there and let
consumers draw their own conclusions."
Soon after the NAHBRC study appeared, however, the group began
to worry that consumers might be drawing conclusions that
weren't supported by the data. "When you rank products from top
to bottom, the ones in the middle may be performing very well,
but they look like they're far down the list," Hill says. "That
can be misleading."
The full-length report, Water Closet Performance
Testing, has been removed from the NAHBRC website
(http://www.nahbrc.org), which now contains
only a brief synopsis of the results. The full report, however,
can be downloaded in pdf form from a number of other sites on
the Internet, such as
Cost and Value
Opinions vary on the relationship, if any, between how much a
toilet costs and how well it works. After comparing performance
data to retail price, for example, the NAHB researchers
concluded that "there is no apparent correlation of price with
performance." A number of toilets retailing for around $50 were
found to perform very well.
Peter DeMarco is adamant that even very inexpensive toilets
can perform well. "If the manufacturer is paying attention to
quality control, cost shouldn't be a factor," he says.
Plumbers, on the other hand, tend to take a different view.
Rex Cauldwell notes that most of his callbacks and installation
problems seem to involve inexpensive builder-grade products.
Burlington, Vt., plumber Dennis Deloy agrees. "If you buy a $39
toilet, you're going to get a $39 flush," he says. "I prefer
Gerbers. They're about all I use, and I've never had any
problems with them."
Terry Love observes that most of the models he's had
consistent success with tend to cost $200 or more. "I install
lots of different brands, but the new Totos are my favorites,"
he says. (Love's website, http://www.terrylove.com, contains his
recommendations for specific models from American Standard,
Gerber, Kohler, Crane, Universal Rundle, Eljer, Briggs,
Mansfield, and other manufacturers, as well as comments from
Old vs. new. Improved
engineering has improved toilet performance overall during the
past decade, but it's worth noting that not all of a given
manufacturer's products will reflect the current state of the
art. New products tend to appear at the high end, while older,
less efficient ones are weeded out at the lower end.
"It's a good-better-besttype thing," says Toto's
Fernando Fernandez. He notes that his company's Standard
Gravity line, which dates from 1994, is still on the market
even though two newer product lines -- which use the larger
3-inch flush valves and more sophisticated trapway designs --
offer superior performance.
"The 'good' product is the builder market," Fernandez says. "I
leave it to the sales guys to convince them to upgrade, but I
wish builders in general were more responsive to some of the
Not surprisingly, most manufacturers show little enthusiasm
for telling buyers which of their products use older
technology. But knowledgeable suppliers will be able to provide
that information, which may be worth knowing in cases where
performance is an issue.
Installation and Adjustment
When a low-flow toilet clogs or fails to deliver a complete
flush, the user often assumes that an old-style 3.5-gallon
fixture would have handled the same situation with ease. This
"good old days" mentality is frustrating to manufacturers, who
are fond of pointing out that plungers weren't invented in
1992. Peter DeMarco notes that flushing is a chaotic, somewhat
unpredictable event. "You can never completely rule out
clogging," he says. "Sometimes the waste will just line up in a
random way that completely blocks the trapway."
On the other hand, because modern low-flows are more precisely
engineered than their predecessors, it's safe to say that they
are inherently less tolerant of error. Plumbers and
manufacturers alike stress the importance of proper
installation, adjustment, and maintenance to trouble-free
Controlling water volume.
When the first underperforming low-flows hit the street in the
early '90s, many plumbers quickly discovered that providing
them with additional water made for a better flush. To avoid
complaints and callbacks, enterprising plumbers often modified
them to use something closer to the familiar 3.5 gallons per
flush. Since most of those fixtures were 3.5-gallon models that
had been adapted by the manufacturer to get by with less, this
sort of in-the-field reverse engineering made sense and usually
worked fairly well.
That's no longer true. If today's better-engineered toilets
are flushed with too much water, their performance will get
worse instead of better.
Rex Cauldwell notes that it's important to make sure the tank
fills exactly to the manufacturer's fill line, and to adjust
the level if necessary. The chain that connects the flapper
valve to the flush lever, he finds, is another common source of
problems. "If there's too much slack in the chain, it will lie
on the flapper and make it close too soon," he says. "I like to
have one or two links of slack when the lever is pushed down
all the way."
Flapper flap. A typical
flapper valve lasts about five years -- often less where
in-tank bowl cleaners are used. When the original flapper wears
out, the homeowner frequently replaces it with a generic
flapper from the hardware store. This can mean trouble, because
replacement flappers often release much more water than the
original manufacturer-supplied valve.
In the NAHB tests, for example, all of the new toilets were
found to use close to the mandated 1.6 gallons per flush. In a
second round of flush tests, using generic replacement
flappers, water consumption shot up to an average of nearly 3
gallons per flush. Other researchers have come up with similar
results. To prevent customer dissatisfaction down the road,
it's a good idea to stress the need to use the right