
T
o fully appreciate the seven high-end
electric-ush toilets that Practical
Sailor recently tested and featured in this
article, it helps to understand how they
are designed to combat the loathsome
clog.
With manual-pump heads, clog resis-
tance usually depends on the discharge
pump’s ability to pass bulky material—
baby wipes, feminine hygiene products,
paper towels, and other fibrous paper
products—the sort of stu that shouldn’t
be in a marine toilet in the rst place. Typi-
cally, water and material is moved toward
the holding tank with a piston pump or
diaphragm pump, both of which can push
fairly bulky items into the discharge hose.
Backow from the tank is prevented by
check valves, typically a apper valve, and/
or a exible tricuspid or duck-billed valve
that allows water flow in one direction.
ese, too, can allow some surprisingly
large objects to pass into the plumbing sys-
tem. (See Practical Sailor, September 2000.)
In fact, in the days of raw-water intakes
and direct overboard discharge, the abil-
ity to ush such things as a glove or sock
were badges of honor among toilet makers.
e old bronze Wilcox-Crittenden Skipper
and the Lavac are examples of heads that
don’t inch when you ush a baby-
wipe. An ability to ush big stu is
ne, provided you have an endless
supply of seawater for ushing and
direct overboard discharge.
However, with holding tanks
now the norm, anything that
makes it past the check valve winds
up in a holding tank. In a perfect
world, what goes into the tank is
easily pumped out, but as anyone
who has spent some time at a ma-
rine pumpout station can attest —
we do not live in a perfect world.
To complicate matters, the trend
toward freshwater ushing, which
reduces odor problems, leaves less
water available for ushing. Enter
the macerator pump. Like your
sink’s garbage disposal, macerator
pumps chop up material into ner
parts, creating an emulsied mix-
ture that can ow freely through
the system without building up.
For many years, head macera-
tors had a serious image problem.
They were loud and they didn’t
work. A common design incorporated an
impeller to move water and some rotating
blades to chop the solids. Typically, both
components shared the same motor
sha. Neither was very good at its re-
spective job, especially once a wad of
paper wrapped around its blades. Clogs
were frequent. Today’s macerators are
signicantly dierent.
In the mid-1990s, the Italian com-
pany Tecma (purchased by Thetford
in 2003) changed the perception of
macerators with the introduction of a
high-speed centrifugal “Vortex” pump,
which had a unique convex rotor and a
funnel-shaped casing or “volute” that con-
verts kinetic energy into pressure. Other
makers soon followed suit with similar de-
signs. Akin to a common bilge pump, the
centrifugal pump has a set of curved blades
on a rotor. e fast-spinning rotor creates a
change in pressure that can quickly push a
“slug” of liquid through the system, using
very little water and making far less noise
than the earlier renditions.
When combined with cutting blades
located on the rotor itself or the pump
housing, the pump is also very eective at
chopping down some surprisingly tough
material. Apart from the more obvious dif-
ferences in sizes, shapes, and buttons for
ushing, the subtle distinctions in pump
design are what set apart the toilets in this
test.
Toilets in this round of testing (foreground) were
very close in size to a common household toilet.
The Raritan Atlantes Freedom has a
clear access panel to check for clogs in
the macerator pump.
A quiet revolution in macerator design has
re-shaped the way we think about heads.
Electric-flush Toilet
Face-off, Part Two
Reprinted from March 2011 …
Kommentare zu diesen Handbüchern