Oh,
what a boring subject, right? Yeah, I agree, reading about bilge
pumps is not too thrilling. But this is a subject which I've been
harping on for a long time, apparently without a lot of success
based on the continuing and overwhelmingly casual attitude that
boat owners have for their bilge pumping systems.
Just to give you a little background, I come
from a family where marine surveying is something of the family
tradition. Years ago, a large part of our family business was
handling marine insurance claims. The hundreds of boats that sunk
every year helped contribute to a very brisk business. Having
spent many years investigating why they sank, I think I have a
pretty good idea why. Its the casual attitude of both boat builders
and boat owners toward bilge pumps.
Sail boaters are the absolute worst in this regard.
For some strange reason, many of them just don't think that bilge
pumps are important. Somehow they rationalize the idea that nothing
is ever going to cause their hulls to suddenly flood, so a minimal
pumping system is all that is really needed. As in just one pump.
I never ceased to be amazed at the number of sailors who argue
with me that one pump is enough. After all, the builder built
it that way, and they have that nifty manual pump back there in
the cockpit and that can really pump a lot of water. More about
that later. FYI: Proportionately more sailboats flounder at sea
even though powerboats outnumber them 8:1.
Of course, sailors are not alone in this attitude.
For every sailor who thinks little about bilge pumps, there are
probably three power boaters with the same attitude. So why the
widespread lack of concern? Well, its the same old problem of
lack of experience; its not until they have a problem that they
become convinced of the seriousness of it. Its mainly the people
who've had their hulls flooded or even sunk that take the matter
of bilge pumps seriously. Its called learning the hard way. I
can understand that. As a kid, I owned numerous small boats, and
I can't begin to count the number of times they sunk because it
rained hard, or the boat was leaky, and I had no bilge pump at
all. Or if I did, I wasn't paying attention to whether it worked,
the batteries stayed charged or whatever.
Unfortunately, sinking at the dock can be the
least of your worries. The situation that can really get your
attention is when you are at sea and something really big goes
wrong, and now you are faced with the prospect of the boat going
out from under you. Like having an exhaust hose fail and the engine
pumps your hull full of water without noticing that until its
too late. That one happens a a lot. Or a sea cock or other through
hull fitting lets go because of some corrosion activity that went
undetected because the sea cocks which are now 12 years old had
never been taken apart and inspected. That happens a lot too.
But when it happens at sea, and the boat has an inadequate pumping
system, you've got a disaster in the making. And if you've
got your family aboard with you, well you may have to live with
a guilty conscience for a while.
Let's start with the premise that next to the
integrity of the hull, the integrity of the bilge pumping system
comes next. Not the sails, the engines, the interior furnishings
or the fancy electronic gizmos, just the plain old, lowly bilge
pumping system. Bad things happen, that's why the government mandates
that you carry life jackets aboard. But an even better approach
is to have a good pumping system so that you have potentially
less need for those jackets.
What Makes for an Adequate System? This
is a question I've been struggling with for years. Unfortunately,
there are no pat answers because the criteria for an adequate
pumping system depends on the style of the boat, not merely its
size. Some types of boats are more vulnerable than others, like
sport fishermen and open boats. In any case, for every type there
is a basic minimum. The table below lists what I think that minimum
is based on boat length.
Boat
Length |
No.
Pumps |
Total
Capacity - GPH |
| 16
- 20 |
2 |
2500
|
| 21
- 26 |
2 |
3000
- 3500 |
| 27
- 35 |
3 |
3500
- 4500 |
| 36
- 42 |
3 |
6000 |
| 43
- 49 |
3
- 4 |
8000 |
| 50
- 59 |
4
- 5 |
9000
- 10,000 |
| 60
- 60 |
4
- 5 |
10,000+ |
There are two factors which must be considered,
the capacity of pumps and the number of pumps. The number of pumps
is important from the stand point that bilge pumps are not reliable
because they are electrical devices submerged in water. Contrary
to common belief, the pumps themselves rarely fail; its the electrical
system from which they operate that is usually the cause of the
failure. Because of this, one way to improve reliability is with
redundancy, or increasing the number of pumps to decrease the odds
of complete loss of pumping ability.
Added to the equation is the fact that the pumps
are only as good as the battery system supplying power to them.
There's not much point in having a good pumping system if the battery
system is not up to running them for the necessary period of time.
We'll get into more about that in the Battery Power section later.
Evaluate the Number of Compartments
While the table above gives us a general idea of how many pumps
are needed, it can't take into account how many compartments there
are in the hull that need to have pumps. Every hull is different,
so you have to evaluate your boat from the standpoint of the number
of compartments that need to be fitted with pumps, as well as the
best location to have redundancy. To evaluate the number of pumps
you need, take a look at the hull and determine where the low point
in the bilge is. Water will accumulate at the lowest point, but
you need to know where that is. Next, determine the number of water
tight compartments or hull dividers such as bulkheads or high floor
frames that prevent free flow of water from one section to the next.
That means determining whether there are limber holes in those dividers
or bulkheads.
As a general rule, every compartment that doesn't
allow free flow of water from one to the other needs to have a bilge
pump. At some point, water can rise in this compartment until it
finds a way to flow through the bulkhead (such as all those holes
for wiring and plumbing) or over the frame into the next. And while
this may not sink the boat if this happens, rising water in a compartment
can cause a tremendous amount of water damage. This is actually
more of a problem in small boats than large ones. That's because
small boats often have very shallow bilges where a small amount
of water in the bilge can end up flooding the cabin sole and cause
damage. Yet this can also be a problem for shallow bilge sailboats.
Especially for planing power boats, keep in mind that bilge water
will flow to the stern while underway if there is free communication,
or it will be stopped at water tight compartments. That's why you
need to evaluate carefully the location pumps need to be installed.
Determining the Number of Pumps Now
that you know the number of compartments that need pumps, we next
relate this to where the water goes when the vessel is at rest,
and while underway. For sailboats, that's pretty easy because the
fore and aft trim doesn't change much, so the center bilge is usually
the target area. For most powerboats, the water will accumulate
in the mid section at rest and aft while underway. Based on that,
you will need the redundancy at these two locations. Any other compartments
can get by with only one pump, of a size and capacity needed for
normal dewatering.
For any twin engine powerboat over 35 feet (generally
excluding trawler types), having four pumps is a good idea; you
want the back ups at both points where water will accumulate. For
outboard or stern drive boats with the engines aft, the water will
always run aft, so the back ups are only needed at this location.
For sailboats with a keel sump, this is the only location
where redundancy is needed, except for larger boats with a dedicated
engine room that definitely should have dual pumps because of the
potential for plumbing system failures, a damaged stuffing box,
exhaust system and the like.
Outboards and Stern Drives These
boats require special attention to pumping systems because of the
weight of the engines. Any water in the bilge runs aft and it requires
very little water to sink them, particularly when they have self
bailing cockpits. A back up pump should be considered a necessity.
The pumps should not be located under the engine where you can't
see or reach it. If it is, move it forward to where you can
reach it.
The problem with most of these boats is that they
have no battery charger, so as soon as the batteries depletes, the
pumps don't work. That's another reason so many of them sink. The
only reasonable option is to install a marine charger and shore
power system. Adding larger batteries will help, but somehow you
have to keep them charged up.
Capacity of Pumps I will start
here with a word about those little 4" square boxes that companies
that make them call bilge pumps. Yep, I'm talking about the Rule
500 and 800 pumps. Only a fool would believe that one of those things
could pump 500 gallons per hour; they can't and they don't, not
even in a horizontal direction, yet alone vertically. I am absolutely
adamant that those things should never be used as a primary bilge
pump. Not only is the capacity inadequate for just about any boat
except a dinghy, all it takes is a bit of string or hair tangled
in the impeller to bring it to a halt. They're okay for use for
dewatering small areas where water might accumulate -- like outboard
of stringers, but never as a primary pump.
Except for those little buggers, there's no doubt
in my mind that Rule makes the best pumps so I'm going to use these
as examples. The most common sizes are the 1500 and 2000 pumps,
with big leaps up to 3700 and 5000. We've tested many of these pumps
and the one thing to be aware of is that they do not pump at those
rates. As near as I can tell, those numbers are for pumping water
horizontally, but when you have to pump the water up and out (called
static head) those numbers will drop dramatically, by 50% or more
when you're moving water up 3 to 4 feet.
My concept of the ideal pumping arrangement is
to have two pumps at the one or two points where the water accumulates,
at rest and underway. Let's say you have a 40 foot power boat. In
that case I would choose the Rule 2000 and 3700, two of each, using
the 2000 as the primary pump and the 3700 as the back up.
Why not the other way around? Mainly because the smaller pump has
a lower power demand which is more desirable for normal dewatering.
No need to be activating the high capacity pump for everyday needs.
The 3700 serves as both a back up AND an emergency pump. The 3700
has a 19 amp draw, which can deplete batteries fast; in an emergency
situation, you will run the engine to keep the batteries charged.
For sailboats, you really have to pay attention
to how high the water is being pumped. Needless to say, a weak,
a low capacity pump is not the way to go. For a 40 foot sailboat,
pumping the water up 3 feet or more, I'd consider two 3700's the
best choice. I have seen 2000 pumps four feet down in the keel with
only a small stream of water dribbling out the side. Don't forget
that resistance in the discharge plumbing also retards the flow.
What Brand? After several decades
of seeing these pumps in service, I have no qualms about
recommending Rule pumps; they're the best. They are, of course,
centrifugal impellor pumps that will not pull the last 1-1/2"
of water out of the bilge. If you want a dry bilge, the only way
to get one is with a diaphragm pump, and your option there are the
PAR pumps (Short for Peters And Russell, now ITT Jabsco).
They are less reliable, but they have the advantage of being repairable,
whereas Rule pumps are not. I don't recommend PAR pumps as anything
but secondary pumps for dewatering as their capacity is very low,
6 gpm or less. These pumps should only be mounted in a dry, dry,
dry location. Neoprene impeller pumps are also available, but I
don't recommend them unless you know how to use them. They will
burn up if they run dry, so you can't turn it on and walk away from
it. If you use either of these types, you MUST install an inline
filter to prevent debris damage to the pump.
Pump Installation Considering
the need for redundancy, there are two ways to install back up pumps
. You can install both at the same level in the bilge and locate
the float switch for the reserve pump up higher, say 6 - 10"
so that it will be activated when the primary pump fails or can't
keep up. The alternative, which I prefer, is to mount the switch
and back up pump itself up higher (Illustration below). The reason
for this is the tendency of debris in the bilge to foul the impeller
over time; mounting it higher up precludes this. In either case,
the installation should be arranged so that the back up pump takes
over at a predetermined water height. Preferably this should be
at a level before water rises above the cabin sole (or any equipment
in the bilge like batteries) and causes damage.
Float Switches Those wonderful
little buggers. Doncha love 'em? Yes they suffer a high rate of
failure and you're always wondering why someone can't invent a better
one. Well, devising a better switch would be easy. Problem is, you
wouldn't pay the cost of the thing, so we have to suffer with what
we got. Actually, most switches fail not because of lousy switch
design, but because of thoughtless installation or lack of maintenance.
These are not self-cleaning devices. There are four things
you need to consider for reliable switch installation: (1) no debris
in bilge, (2) nothing should interfere with the rise and fall of
the switch, (3) it must be wired properly, and (4) it must be protected
from the surge of water in the bilge.
Open Versus Covered Switches.
The enclosed float switch would seem like the ideal solution to
switch fouling problems except for one thing: you can't see or test
the switch. Further, the enclosed switch is just as likely to become
clogged with sludge and things like hair in the bilge as the open
switch. Only now you can't even see it. The only problem they really
solve is water surge damage. The open switch is the better choice
as long as you clean it once in a while, and locate it so that its
protected from water surge.
| Note: Sludge is formed
when oil in bilge water adheres to surfaces and then collects
dirt. Eventually it becomes a tar-like substance that
will prevent the float switch from moving. |
The switch can easily be protected from surge by
simply locating it within 3" of a bulkhead with the flapper
facing AFT. Always AFT. See my point? If surging water catches the
flapper from the front, it tears the flapper off its hinges. Okay,
now that problem is solved. The next one is that you have to keep
your bilge clean. Nothing, but nothing is going to survive a bilge
with sludge and debris in it. Finally, all your wires and hoses
have to be secured to that they don't move and end up sitting on
top of the switch. Don't forget boats bounce around a lot; those
things have to be well secured.
It would be my guess that well over 50% of all
pump failures are caused by water getting at wire connections and
causing corrosion and high resistance. People just don't realize
that corroded connections cause a power loss that can either cause
the pump to burn up, or the wire connections to overheat and terminate
all power flow. That's why its imperative that the wire connections
be made as high above the bilge as possible, and that they be protected
against getting wet from any other source, like water dripping from
above.
Doing It the Right Way I
recommend that the connections be made using a covered, plastic
junction box, the one hole type (Such as the Carlon boxes you can
get for a few bucks at Home Depot), mounted on the nearest available
vertical surface. Obtain a small terminal block, preferably with
brass terminals. If you can't find small ones, cut a larger one
in half; they're made to be cut. Attach ring terminals on the wires,
wire it to the terminal block, and put the terminal block inside
the junction box and install the cover. You can leave the terminal
block loose inside the box so you can pull it out to check or repair
connections. Be sure to mount the box with the wire hole at the
BOTTOM, not the top! This is a particularly good way to install
pumps in open boats and under cockpits where leaking and condensation
sweating is a constant problem. Forget about butt connectors, electrical
tape and silicone and heat shrink; none of these solves the water
problem.
The Discharge Outlet Its amazing
that after all these years, so many boat builders still do not know
how to properly install the discharge plumbing. You'd think any
fool would realize that you can't just pump it out through a hole
in the hull a couple inches above the water line without the water
flowing back in. But they don't.
The discharge outlet is usually placed near the
water line because the splash from the discharge goes up on the
hull side and makes a mess. So the motivation here is no splash.
Fine, but you have to do something to prevent water from coming
back in. That something is called a riser loop. The riser loop extends
the discharge hose well above the water line to prevent this. Of
course, if for any reason that discharge should go below the water
line, you are right back to the reverse siphoning problem again.
Unfortunately, there's no good way to deal with this short of raising
the discharge higher up. Syphon breaks and check valves are notoriously
unreliable because of their tendency to get clogged.
|
| How not to install a bilge pump. You
can see by the high water line that it has already failed.
The hoses at left were restraining the float switch and the
wire connections were laying in the bilge water. They were
moved prior to taking this photo. The builder installed it
this way. |
For power boats, I recommend a riser loop height
of about 18" above the water line. For sailboats, you have
to consider the heel angle of the hull, which means that it will
probably be tapped into the cockpit scuppers or sink drain. Here
you have to be real careful of judging the water line right. Sink
drains often aren't high enough to tap into it safely, so be sure
to check the water level carefully. Its also not a very sanitary
thing to do.
Teeing into existing lines is okay as long as you
understand what you're doing. The T must always induce water into
an overboard on the vertical, never the horizontal plane. This is
to obviate any possible backflow. Its best to use a 30 degree angle
fitting; a 90 degree T causes turbulence and reduces water flow
greatly.
When adding new pumps, you can avoid making new
holes in the hull by increasing the diameter of your existing outlet
-- say from 3/4' to 1-1/4" and adding a manifold. No, you can't
double up on a 3/4" outlet because its too small and will not
handle the increased flow and will restrict the pumps. Just buy
a larger fitting and increase the existing hole size. If you find
it easier to drill another one, by all means do that. Nor should
you ever double up on a plastic t-hull because it will break; if
you have plastic, you MUST replace it with bronze. If you do add
a manifold, make sure that the lever arm it creates is supported,
whether its horizontal or vertical. Also make sure that the hoses
are well supported so they don't kink.
Emergency Pumps - Who
Should Have Them and Why "It can't happen to
me." That's the attitude. Just as people head out to sea without
a life raft, so do they go cruising without a high capacity emergency
pump in the event something goes wrong. But it can happen, and it
does happen, to all those good folks who thought they'd never need
it. Every time you head out, the odds increase that it will happen.
Anyone who does any long range cruising should
have an emergency bilge pump. No, I'm not talking about one of those
hand pumps. Anyone who's ever tried to work a hand pump for five
minutes knows that these things won't do. Even a man in good physical
condition can operate one of these things for very long. A typical
disaster that could have been prevented by an emergency pump is
the loss of a propeller shaft or a rudder, which opens up a hole
just large enough that ordinary bilge pumps can't handle. That's
where an engine driven pump can save your boat and your life. If
you're going cruising, you should have one. Period.
Yes, they are expensive to install, but they can
be MORE valuable than life rafts or life jackets because it may
obviate the need to ever use these things. The idea is to keep you
from having to abandon your sinking boat. Engine driven pumps are
very high capacity with the volume being controlled by engine speed.
They are more reliable than electric pumps because they're mechanical.
The average size pump runs about 50 - 65 gallons per MINUTE, and
that's a lot. An honest 3000 GPH, a capacity that can deal with
some serious hull flooding.
For smaller sailboats, installing one can be more
difficult because there's no space at the front of the engine. The
solution is to add a pulley to the propeller shaft and drive it
from there. It has to be operated with the engine in gear, but it
will still do the job. You may be able to find a split pulley (in
2 halves) that will make installation a lot easier. Instead of having
to remove the coupling, all you have to do is drill a slight detent
hole.
Shown in the photo below is another good option,
a suction take off from the main engine pumps. Its a whole lot cheaper,
but the only draw back to this arrangement is that if you run the
engine pump dry, you burn up the impellor and now you've got another
problem. This arrangement is a lot cheaper than adding a belt driven
pump, but if you go this route, make sure that you understand what
you have to do to operate it without wrecking the engine. It takes
two people. Also make sure the T-off is BEFORE the sea strainer
so that you're not sucking up bilge debris into the engine.
Battery Power Okay, we've
covered just about everything with the pumping system except the
power source. For larger boats with big batteries, this is rarely
a problem. Its a huge problem for small boats where all the
builder saw fit to provide were an el cheapo car battery or two.
I don't care that it says MARINE on the side of it, it you're got
those brightly colored, thin casing plastic batteries, its
not a marine battery. I don't care if it says "deep cycle"
or that it can light up the universe, I've yet to see one that isn't
a piece of junk. My auto mechanic tells me the same thing; the average
car owner is replacing batteries every two years because they are
junk, junk, junk. Just a big sales racket.
If you want to save bucks by using cheap car batteries
in your boat, you've wasted your time reading this because your
pumping system is no better than the batteries that run it. Batteries
die, pumps die. Here's the deal: as batteries age, the amount of
charge they hold begins to drop dramatically. Two 14 amp pumps equals
28 amps, and wired to a common 60 ampere hour battery means that
the two pumps would theoretically exhaust a new battery in two hours.
But it never works out that way because as the battery declines,
its ability to provide power declines at an accelerating rate. When
the battery is older, the problem is even worse. The average one
year old 60 AH battery will barely run a 14 amp pump for 30 minutes.
And if you have to pump that water uphill, it gets even less than
that because the pump is straining at maximum current draw.
Do you get the picture? Take it from someone who
has screwed around with cheap batteries most of his life, it is
not worth fooling with those things. Go for a heavy duty commercial
or marine battery. Surette, American, Exide, any of the big battery
makers. You can tell if its for real if its big, black, very heavy
and costs twice as much. Good batteries are heavier because they
have more lead, for one thing. You are better off with one size
8D battery than you are with two smaller, cheap ones. Capacity is
DIRECTLY related to size. Paring up two small ones is no match for
one large one. An 8D (250 AH) costs about $250.00; two 90 AH auto
batteries are going to cost around $100 each, so the cost isn't
that much more. A pair of 4D (125AH) will work nearly as well.
Wiring Pumps The common
mistake in wiring pumps is to wire them after the shutoff switch
or the main circuit breaker on the panel. It happens often that
someone turns off the main power without realizing that he is also
shutting of the bilge pumps. To test whether your boat is wired
wrong (and many are) turn all the power off and then test the pump
by lifting the float switch. If it doesn't go on, then you know
what the problem is.
I do not agree with the ABYC standard that bilge
pumps must have circuit protection. Far too often, the circuit breaker
or fuse is the cause of a boat sinking. If you want to eliminate
circuit protection, try to keep the wire run as short as possible.
While its not good practice to wire anything direct to the battery,
I'd say the lone exception would be bilge pumps. If there's no other
practical way, go ahead and do it. This applies to submersible pumps
only. These pumps have no history of burning up and starting fires.
When adding pumps, the easiest way is to purchase
the small Rule three-way switch panel which has an indicator light
too. Where to find a power source can be one of the more difficult
tasks, especially if you're adding a pump up forward. Don't make
the mistake of tapping off some other equipment or bus. Take the
time to string the wire right. Your options are to go to the main
panel, direct to the battery, or from the terminals on the back
of the battery switch, making sure that you get the one that's always
energized. In most cases, going direct to the battery will be easiest.
No doubt someone will send me an e-mail saying
"How dare you recommend violating the rules," but I am
not telling you that you must go to the main panel because with
many panels that is nearly impossible to do.
Related reading at Dockside
Reports:
Bilge
Water Blues - Solving the Problem of Leftover Bilge Water
|
