flushed, the valve opens to the drainpipe
leading straight down to the holding tank
below. Water is simultaneously pumped into
the bowl to complete the cleansing. These
are about as simple an installed unit as you
can get, so they are popular with low-end
tour and ferry boats and such. They have lit-
tle to go wrong and are inexpensive, but the
smell wafting up through the sewage pipe
when the valve is open to flush is pretty
strong. I would use at least double the recom-
mended air-change rate from Table 14-1 for
any such toilet compartment. Also, install
commercial deodorizers and pour deodorant
into the holding tank.Traditional Marine
Pump Toilets
The traditional marine toilet uses a
simple plunger pump: a standard positive-
displacement pump. These have a joker valve
(flapper valve) that is subject to clogs, but
otherwise they are the old reliable. They do
tend to use a lot of water. The best manual
joker-valve toilets have very large diameter
pumps—as large as 4 inches (100 mm) ID,
such as the Wilcox-Crittenden Skipper II. The
large diameter makes them less likely to clog.
Typical low-cost, plunger-pump toilets will
have around 1^1 / 2 - to 2-inch ID (38 to 50 mm)
pumps. They will work acceptably but need
more care to avoid clogging. The smaller di-
ameter uses somewhat less water per flush,
however. These pumps can be motorized, but
if you’re going to do that, it’s better to go with
a macerator-pump toilet.Electric Macerator-Pump
Toilets
One way to minimize the chance of clogs in
a standard water-pump toilet is to grind up
the effluent into a fine slurry. This is done in
macerator-pump toilets. These work quite
well, though their water usage is only average
at about 1 to 2 quarts (0.9 to 1.9 L) per flush
(leaning closer to 2 quarts or 1.9 liters for
most models). Raritan’s Atlantes is a good
example of this toilet, and my office has spec-
ified this model on larger yachts with luxuri-
ous head compartments because it’s quite
modern and stylish. The drawback over, say,the Blakes Lavac is the extra electric and me-
chanical systems and parts. Another model
is Wilcox-Crittenden’s Newport electric mac-
erating toilet. It is quite economical in water
use, at around 1.5 pints (0.5 L) per flush.Vacuum-Flush Toilets
(Manual and Powered)
Vacuum-flush toilets draw water through the
system via suction ratherthan pumping a
column of water. The Blakes Lavac is an ex-
ample of a manual vacuum-flush toilet
(which can be motorized with an electric
pump). SeaLand, Groco, and others make a
wide assortment of vacuum-flush toilets.
SeaLand calls their models VacuFlush, and this
term is often used for all powered vacuum-
flush toilets. Most vacuum-flush toilets are
quite water thrifty, quiet, and resistant to clog-
ging. SeaLand’s VacuFlush models, for exam-
ple, are around 1.5 pints (0.5 L) per flush.
Again, the drawback is the extra complication
of the powered pump and its electric demands.Water-Jet Macerator Toilets
There are also water-jet macerator pumps.
These use a powerful jet of water blown
into the toilet to flush. Since the pump is be-
fore the toilet, it is virtually clog free, and
the water jet is arranged to macerate the ef-
fluent as it is pumped out. Headhunter is one
manufacturer of these pumps, which have
passed women’s stockings, shirts, and other
objects that would clog nearly any other type
of head. These pumps can be installed as in-
dividual units, but particularly shine on large
boats where five, six, or more of these toilets
can be driven off a single, central pressure-
water pump with a rather large 1-inch (24 mm)
delivery pipe. (Often all the toilets share the
same holding tank as well.) The pressure-
water pump—entirely before the toilets—-can
be the same pump used for the domestic fresh-
water system.Freshwater for Flushing?
This brings us to the refinement of using
fresh water for flushing. I’ve never been en-
thusiastic about this, because fresh water is
a limited commodity aboard, and there’s
plenty of seawater available at all times.PART SIX:PLUMBING SYSTEMS WITH NOTES ON FIRE SUPPRESSION