People
are often baffled by the problem that the typical
rotary vane bilge pump (such as Rule) does not remove
all the water from the bilge. In fact, most pumps
will leave as much as 1-1/2" of water. Plus there
is also the matter that the remaining water in the
hose when the pump turns off then runs back into the
bilge.
| Parts
Needed |
| 
diaphragm
pump
Jabsco - PAR single diaphragm
pump
|
Bilge pump switch
with indicator light |
| 
Bronze mushroom
head through hull port with a barbed 90 degree
elbow
|
Pickup strainer |
Liquid Electrical Tape |
Additional
Reading: |
All
About
Bilge Pumps "Those
Essential Devices for Keeping Your Boat Off
the Bottom"
|
And no,
you should not use a check valve in the bilge pump
line to prevent the back flow of water. The use of
a check valve is not recommended due to the potential
for sticking and causing the pumping system to fail.
On a sail
boat with a deep keel sump, that's probably not a
problem, but on a power boat where the bilge
bottom may be nearly flat, that much water remaining
in the bilge can cause big problems. For one thing,
when the boat gets up on plane, all that water is
likely to go rushing aft where it sloshes and splashes
around, causing corrosion damage to other things under
the deck that shouldn't get wet.
Further,
when the weather is hot, and the sun is beating down
on the deck, this causes a high evaporation rate that
creates very high humidity in the bilge that can cause
other components, especially things like steel pump
bodies and generator sets to rust up. Therefore, it's
a good idea to remove as much of that water as possible.
Fortunately,
there is a solution for this, which is to install
a diaphragm pump that is capable of removing
nearly all of the water from the bilge. Usually, these
can remove up to the final 1/4" of water. For
this purpose, we recommend the Jabsco
- PAR single diaphragm pump, shown at left
top, which is reasonably priced. We like it because
it has mostly plastic parts that don't rust, and the
diaphragm can easily be replaced. You'll also need
to have an inline strainer so that no debris gets
into the pump, but fortunately this is provided
with the pump.
This is
a low capacity pump of only 3.5 gpm. It will do the
job just fine, but if you'd prefer, you can choose
a pump with higher capacity to use as a reserve or
back up bilge pump.
Naturally,
this pump has to be operated manually since no float
switch can function in an inch of water. Therefore,
it gets wired to a manual on/off switch
The installation
of such a pump is straightforward. First, you need
to determine where is the lowest point in the bilge
when the boat is at rest, and where the water will
accumulate. This is the point to install the pump
and it's remote pickup. The beauty of this type of
self-priming pump is that it can be mounted well above
the bilge water and out of harm's way of leaking hatches
where water might get to it.
Secondly,
consider what and where is the best way to route the
discharge hose overboard. While it is possible to
use existing through hull ports, care must be taken
in the manner of accomplishing this so that water
does not back flow through any other hose that
is connected to the port. The usual method of doing
this is to have a riser loop on both discharges and
have these hoses routed downward to the hull port.
To accomplish this, install a "Y" elbow
in the existing line as per the diagram. Note that
you can use sink discharge lines with the caveat that
you will hear the pumping noise up through the sink
drain. But since this is not an automatic pump, but
one that will only be used occasionally, that may
not be an important consideration.
You can
also double up to an existing bilge pump port by the
same method. Your existing pump should have a riser
loop already in the line, in which case all you need
to do is install the "Y" and duplicate the
riser for the new discharge line. It's wise to have
a riser of at least a 12" above the waterline
for power boats.
If you're
going to put a new hole in the hull, we recommend
a bronze mushroom head through hull port with
a barbed 90 degree elbow. This will enable you
to run the hose upward for your riser loop without
having to make a too-sharp bend. If the hull side
is cored, you should NOT cut a hole in it unless
the builder has provided an uncored area specifically
for the installation of through hulls. With a cored
hull, it's best to try to double up to your existing
bilge pump outlet.
For the
riser loop, you MUST find a way to secure the riser
loop to the hull. Usually there is no place to attach
a holding strap to. Probably the best way to do this
is to epoxy glue a small block of plywood -- say 4"
x 4" -- to the hull side. Rough up the hull surface
with coarse sandpaper first to be sure to get a good
bond. After the epoxy has dried, then you can use
a ty-wrap to secure the hose in position.
Note:
We do not recommend the use of poly hose due to its
propensity for collapsing and kinking. We recommend
Series 148 Multi-purpose reinforced vinyl hose.
For the
wiring, you should use a spare slot on your breaker
panel if you have one. If not, you'll have to use
an inline fuse, so be sure to place it at a location
that it can easily be reached, but also where it's
not going to get wet. For the switch, we'd recommend
a dedicate bilge pump switch with indicator light,
one such as the Rule model 41,
43 or 45. The later two
models are three position switches, but do have the
benefit of having a built in fuse holder that makes
installation easier.
Use
#12 wire and standard butt connectors. We recommend
the use of Liquid Electrical Tape to seal
the connections.
Total
cost to complete this do-it-yourself job: Approximately
$300.00.
Related
Reading: All
about Bilge Pumps at www.yachtsurvey.com
|
