adequate bilge pumps is next in
importance after ensuring the integrity of your hull.
Don't wait to take the matter seriously until you are woken in
the night by chilly buttocks and you see your shoes sailing in
A boat doesn't even
to be in a collision
or storm to sink, it is quite capable of doing it all on its
All those modern 'necessities' such as the
heads, engine cooling
intakes, stern glands etc, mean that many boats have more holes in
bottoms than a Dutch cheese.
Any of those through-hull
leak even if the seacocks are closed.
The essence of good seamanship is safety.
smallest open boat should have
some means of bailing.
A frightened boater can move a
lot of water with a
bucket, but only if he can get at it and is able to jettison it
A bilge pump is the answer for
any enclosed spaces which
are not easy to get that bucket into.
Even canoes can benefit from
having a small pump
How many pumps your boat
should have will depend on
Every hull is different
however, as a rough, starting
guide, a boat from 16ft to 26 ft / 5M to 8M in length should have at
pumps, 26 ft to 35 ft / 8M to 10M, at least three and anything above
should have at least four pumps.
It is worth remembering that
even on a small boat that one bilge pump is only adequate if it is
And the more bilge pumps you
have the more of your crew
will be able to help with the pumping.
By the same criteria, larger
boats should have at least
one more than the minimum if only as a back up.
Next thing to consider is
where the pumps are to be
A cabin cruiser, for instance
should have one which can
be operated from the cockpit and another from within the cabin and
referring to minimums.
Where the water accumulates is
another criteria to
Any sealed compartments which
don't drain to the
bilges should have their own dedicated pump.
Even if these compartments
won't hold much water it is
worth having a small pump to drain them if only to prevent water
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The next problem is deciding what size or
pumping capacity your pumps should be.
The table I have drawn up below gives an indication of the capacities
should be aiming for however, there are several other factors to take
First do they all need to be the same size?
The bilge pump used for everyday needs, providing you don't have any
serious leaks won't require a large capacity.
And a smaller pump will require less energy to drive it whether its
energy or battery power.
Save your largest pump
On the subject of emergencies, which I sincerely hope none of us has to
with, a large capacity manual bilge pump could be operated by the
members of the crew while weaker members could help by pumping the
The next thing is how high the water has to be raised.
The height the water has
to be pumped vertically up
before it can discharge will reduce the amount the pump will be able to
This is something sail
boaters need to
consider, a pump which discharges on the
windward side will
have to lift the water higher than one emptying on the leeward but the
outlet could be underwater when the boat is well heeled.
The discharge rate will also be affected by the size of the piping,
smaller bore of pipe might reduce the flow-back but it will
the out flow.
When it comes to buying pumps I guess the best advice is to buy the
The efficiency and standard of the better know brands is exceptionally
unfortunately many manufactures complicate the process of choosing by
the capacities in different configurations.
A quotation in gallons or
litters per hour sounds
very impressive but how many of us could pump manually for an hour and
of our batteries would go flat in that time.
And the capacities quoted are rarely related to the height the water
has to be
When choosing, it is best to err on the safe side.
This table below is a very rough guide to the minimum pumping
should be aiming for.
||16ft to 26 ft/5M to 8M
||26 ft to 35 ft/8M to 10M
|US gal. per hour
||2500 to 3500
||3500 to 4500
|US gal. per min
||40 to 60
||60 to 75
|UK gal per hour
||2090 to 2910
||2910 to 3750
|UK gal per min
||35 to 50
||50 to 63
|Litres per hour
||10000 to 13000
||13000 to 17000
|Litres per min
||140 to 227
||227 to 284
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When it comes to
choosing between electric, manual or engine driven bilge pumps I
believe it is
a good idea to hedge your bets
I would feel very vulnerable without at least one manually operated
I know that pumping is
work and few people can keep
it up for long but at least I don't have to worry about the electrics
Another advantage to the
modern diaphragm bilge pump is
that it is self priming.
And they can also be used
pump any stale air or more importantly gas out of the bilges, most have
few metal parts so the risk of causing a spark is
sure to choose one which
can be repaired and serviced
the other hand an electric pump with a float switch is perfect for
peace of mind when the boat is left unattended, providing the switch
the battery system up to running it for the necessary period of
For moving large amounts
water quickly and easily an
engine driven pump has got to be the best option but they are expensive
install and not a lot of use if you can't start the engine.
They also need to be mounted
at the front of the engine
which, for small boats is likely to be an issue due to lack of
Using the engine cooling
intake is not really an option
for small engines as the amount of water drawn by the impeller is not
And it is not worth the risk
of burning out the impeller
and wrecking the engine if it runs dry or it becomes blocked with
For small boats and canoes
there is nothing wrong with
the small plastic stirrup pumps.
However, few can be stripped
down easily so, keep that
bucket or cut down milk or oil carton handy as well.
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The main problem with electrical bilge
pumps is not the pump but the
The modern pump is pretty rugged and reliable.
When they fail it is usually the fault of the power supply.
A big pump drawing a lot of amps can quickly flatten a
For larger boats with several big batteries this is less of a
for small boats. However, all boats have a problem where electricity is
concerned; water and especially salt water!
Any corrosion in wiring connections will increase resistance
While minimising the risks is important for any wiring it is
important for emergency systems.
make sure that
any connections are kept to a
minimum and are as high above the bilge as possible.
Tin the wire ends and use terminal blocks with brass
and place the
blocks in a junction box with the entry hole for the wire at the
Don't try to skimp on wire size and support the wire
cable clamps or ties.
Keep the wiring runs as short as possible but don't be
into the supply for other equipment.
The pumping circuit should be kept separate from the other
independent of the main shut off switch and fuses.
And while it is good practice to protect any circuit with a
fuse or circuit
breaker it might be worth making an exception in the case of the
pump with a float switch.
Whether or not you fuse the float switch check it regularly by
the switch, it should work regardless of whether the main switch is on
Unfortunately float switches are notorious for failing so,
There are several other forms of switch for detecting water
none of which I have any experience with so cannot comment upon.
As far as I'm concerned the float switch is cheap, simple and
easy to check,
clean and replace.
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Fitting Bilge Pumps
There a number of things to bear in mind when fitting
Where does the water collect when the boat is at rest.
And where does it collect when under way.
Inlet hoses in the bilge need a strainer to keep out any
sludge and the like.
Float switches need to be kept free,
clean, and be
Hoses need to be secured so they don't move or
Hoses should be smooth bored.
Emergency float switches should be set high to
and thus wear
but low enough to prevent water damage to the cabin sole.
For everyday pumping the inlet needs to be as low
Locate bilge pumps where they can be easily
Keep pipe runs as short as possible.
The discharge outlet needs to be above the waterline.
Insert a riser loop in the outlet pipe to prevent back
the outlet become submerged.
Always use the size of hose recommended by the pump
manufacturer and that
includes the size of the outlet fitting.
If joining two outlet pipes use a Y connector rather than
junction.Where two outlets are connected the subsequent pipe must
It may seem obvious to place
the pump inlet where the
water collects, on a low powered boat this will tend to be at the same
point both at rest and underway.
However, on more powerful
motorboats the water may
accumulate in the mid section while at rest but run aft when underway.
pumps will be needed in both locations.
switches should always be fitted with the '˜flapper' facing aft to
minimize surge damage.
can also be
sighting the switch aft of a
is fairly common
to place the outlet fitting
low down to reduce the amount of staining by dirty bilge water on the
of the hull.
this can lead to
siphoning unless there is
a riser loop before the outlet.
top of the loop must
remain well above the water line
whatever the angle of heel.
can be a problem for
sailing boats in which case the
outlet is perhaps better sighted in the transom.
own bilge pump outlets drain into
the self draining cockpit, the possibility of any dirty water in the
is, as far as I'm concerned, preferable to the risks of back
You can fit siphon
non-return valves but these
have a tendency clog, better to have that outlet well above the
Having fitted the pumps
next job is to keep those
system no matter how good
will be able to cope for long if the bilges are full sludge and
And make sure that the
holes are kept clear so any
water can drain towards the bilge pump inlets.
And finally make sure that
nothing, especially those
wires and hoses, can interfere with the float switch.