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Keeping the Bilge Dry Installing an Automatic Bilge Pump


By Jack and Alex Wilken ‘Bilge water’, ‘sweet bilge’, ‘dry


bilge’, and ‘that’s a lotta bilge’ are all ways the word “bilge” is used, but mostly we hope for a dry one. Bilges are for the most part unseen, unless we take a moment to lift the cabin sole to see what’s happening. It is possible to monitor or empty them with electronic or mechanical sensors that will turn on an alarm or start the bilge pump. In the “good” old days we would be


referring to a brass tube with a plunger, a bucket, or some such nautical oldie, but today ‘bilge pump’ could mean a manual, engine driven, or electric pump. Although the most popular of these today is the electric bilge pump, all boats still need some kind of manual equipment to deal with flooding in an emergency like when the batteries fail. In this column we will just focus on the electric bilge pump.


Types of pumps There are three types of electric


bilge pumps: submersible, impeller, and diaphragm. The mounting and wiring can be different for each one, and each has its pros and cons. In this article we’ll cover the one which in some ways is the simplest- the submersible pump. These pumps are quiet, with low battery drain, will pump cleanish bilge water without an extra intake filter and


have a high rate of flow as long as the head is low. (‘Head’ is the difference in height between the pump and the highest level of the discharge hose.) For example, one manufacture states a flow of 1000 GPH (Gallons/Hour) with no head or rise in the discharge hose but a flow of 800GPH with a 3 foot head. P.S.I. Head(in feet) 2.1 4.3 6.5 8.7


5


10 15 20


It is also important to use the


recommended hose size since a smaller size will further slow the flow rate. One of the cons of these pumps is that the water between the pump and the highest level of the hose will return to the bilge when the pump turns off.


Diagram 1 Head


Riser Loop


and then the pump snaps into it. (See photos) Depending on the size of the space where you will mount the pump and whether all of the bilges drain to a single low point, you should choose the largest pump that will fit. If you have separate bilges you will need a pump for each. A smaller boat is more susceptible to a leak than a big one because the same amount of water coming in will sink it sooner, so do not buy small based on the size of your boat. If you can fit a 1000 GPH pump, use it. They can sell for less than $50. Choosing the appropriate capacity pump for your boat means deciding what you want the bilge pump system to do. ABYC divides it like this, “These standards apply to all boats equipped with electric bilge pump systems intended for control of spray, rain water, and normal accumulation of water due to seepage and spillage.” and exceptions, ie “Pumps intended for damage control and Damage control systems. We will discuss this in a later article.


Sensors There are two common types of


Mounting is straight forward- it


goes into the lowest part of the bilge (See Diagram 1). Some models come with a base that can be screwed down


sensors that will activate the submersible pump when the water level increases- a float switch or electronic sensor. Some submersible pumps come with a float switch connected to or incorporated into them. This, obviously, simplifies the installation. There are several configurations of the float switch, but mostly it comes down to whether it is in a protective housing or not. (The housing gives you protection from large objects in the bilge, but then you don’t have the ability to reach in there


Bilge pump with mounting base and internal float switch. 48° NORTH, JANUARY 2011 PAGE 72


Mount pump as low as possible in the bilge.


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