PART SIX:PLUMBING SYSTEMS WITH NOTES ON FIRE SUPPRESSION
circulates through a heat exchanger in the
tank, which makes plenty of hot water for
free. A good tank will keep the water hot
several hours. These water heaters are often
calledcalorifiers, because they add calories
(energy) to the water. Nevertheless, when
you’re not underway, not running a genera-
tor (or don’t have one at all), and not
plugged in to shore power, there will come
a time when you’re plain out of hot. The only
answer then is to fire up the engine for
twenty minutes or so to make more—noisy
and inefficient. Still, this is infrequent and
manageable enough that standard hot-water-
heater tanks (calorifiers) are the common
answer for most boats.Flash or Instant Hot-Water
Heaters
The alternative is on-demand hot-water
heaters, also called instant heatersorflash
heaters. These are flash-coil devices that heat
water almost instantaneously as it passes
through. They are small, light, and efficient
and have no large tank to take up space. The
drawback is that they require either LPG
(propane) or a large generator to produce the
heat required. LPG is probably the logical
choice for small cruisers, though you must
take great care with safety precautions in the
LPG system. You must also give careful
thought to location of the hot combustion
exhaust run and exhaust exit, and to making
sure carbon monoxide can’t get below. In the-
ory, generators are even better as a source of
engine-cooling-water heat, but if you have
that much generating capacity, you can
simply use the generator’s electric output to
heat a standard hot-water tank (calorifier). In
spite of the cautions regarding LPG, some
sailors prefer LPG on-demand heaters, as they
may go days without running the engine, and
many have no gen set.
One problem with instant hot-water
heaters is temperature control. On many
units, the first rush of water is too hot, but
then if the water is flowing steadily, the tem-
perature reduces to tepid and stays there.
The best units don’t pull these hijinks, but ask
around and if possible, test any instant heater
you’re planing to install.Freshwater Delivery Piping
The delivery-side water piping should be well
installed to avoid chafing or leaks. You also
need to minimize excess freshwater usage as
much as possible. Dishes in particular can be
washed just fine in salt water. This means
you need a seawater tap at the galley sink.
You could put an electric pump on this, but a
good-quality foot pump (like the Whale
Gusher MK 3) does a fine job and keeps both
hands free. (There are good hand pumps too,
and we’ve installed them, but my preference
is the foot pump.) Make sure there is a recess
that gives plenty of clearance over the foot-
pump pedal so you can get your foot on it
easily to work it.Backup Water
An identical foot pump should be installed on
the cold-water tap at the galley sink as well.
Why? So equipped, you can still pump fresh
water for drinking and cooking even with a
complete electric outage. This foot pump
needs to be supplied from a separate, dedi-
cated pipe from the tank (right after the fil-
ter but before the pressure pump) because
the foot pump can’t take the pressure from
the water-pressure pump. The cold pressure-
water line tees into the riser to the faucet tap
above the foot-pump line, with a check valve
(a one-way valve) to further protect the foot
pump from excess pressure.High-Quality Filtering
On most of my office’s designs, we install a
charcoal filter on the cold-water line at the
galley-sink mixer tap. This means that the
fresh water you use for cooking, making
coffee or tea, and for most drinking is double
filtered—first through the mesh filter/strainer
right after the tanks, and then through the
charcoal filter. The head sinks and the show-
ers aren’t used much for drinking, so you
really don’t need charcoal filters there. On
larger boats, you may want to run the cold
fresh water to a single common-rail manifold
(see Figure 4-9) and have a larger charcoal
filter just ahead of the manifold or even a
combined charcoal and UV filter. This way,