CHAPTER 18
Bilge Systems
It’s unquestionable that the first job of any
boat hull is to keep water out. Failure in this
will result in water damage, loss of stability,
and even sinking. Even so, water will find its
way aboard through drips in windows,
through hatches and ventilators, and through
rain and spray entering any opening. In storm
conditions, solid water will come on deck.
This, too, will find its way below through
everything from chain pipes, to hatch gutters,
to vents, to a door left open too long. Then of
course, there are leaks in the hull itself. These
could be small drips from packing glands,
more serious inflow from damaged fittings,
or—the worst fear—a sizable hole from ma-
jor impact. As we’ll see, even a seemingly quite
small hole below the waterline can admit a
substantial amount of water and do so quickly!
Accordingly, all boats must be fitted with
a bilge system to remove bilge water. A
rugged and reliable bilge system is crucial to
safe vessel operation. The bilge system pri-
marily consists of- a pump or pumps
- piping and fittings to transfer water
from inside the boat back out to the
surrounding sea - a power source to drive the pumps
Of course, small open skiffs, canoes, and
kayaks don’t have bilge systems. A hand
bailer or a bucket and a sponge do the job. As
boats grow somewhat larger, however, a
proper bilge pump must be installed.
Under about 20 feet (6 m)—if the boat
has no electric system—a manual bilge pump
will make up the bilge system. If fixed (bolted
in place), it has to be fitted with the appro-
priate hose and piping to take water from the
lowest part of the bilge where water collects
(the bilge sump) and discharge it overboard.
To prevent clogging, the intake opening
should be fitted with a strainer called a strum
box (Figure 18-1). (There may be exceptionsFigure 18-1. Strum box (Courtesy Edson
International)