Dewatering Equipment for Inshore Sailing

Dewatering Equipment for Inshore Boats

Most boats in use today are made of fiberglass and have to deal with only minor leaks. Bilge pumps are small, quiet, and tend to be forgotten - out of sight, out of mind. These pumps will quickly become the center of attention when a burst hose or damaged hull is letting in hundreds or thousands of gallons of water per hour.

This topic covers "dewatering equipment" (the US Coast Guard term for "pumps") on boats being used for daysailing, coastal sailing or ICW travel. See the separate topic on offshore dewatering for boats that sail out on blue water. See also the related article on tools and supplies for damage control.

Small Boat, Small Pump, Right?

You might think that small boats only need small bilge pumps, but the opposite is true. A small boat with a smaller bilge capacity will fill up and sink faster than a large boat with the same sized hole. Most production boats are delivered with bilge pumps that are just adequate for handling rainwater and the drips from your prop shaft, but can't handle the large amounts of water that would be let in by a hole in the boat. If you travel far from shore, consider upgrading your bilge pump, wiring and hoses.

5 Tips for a Better Bilge Pump System

Try this test when you're tied up at a dock. Take your fresh water hose and time how long it takes to fill a 5 gallon bucket. Now, turn off your bilge pumps and see how long it takes to fill your bilge. You can estimate how many gallons you bilge holds by multiplying the gallons per minute rate from the bucket test by how long it took to fill the bilge. Now, turn off the hose and turn on your pump(s) and see how long it takes to empty the boat. This test will give you a good assessment of how big your bilge is and how fast your existing pump(s) work.

Now, consider the rate at which a hole in your boat will admit sea water. If, for example, your 1 1/2" diameter transducer for the depth sounder is damaged, and the transducer is only 2' below the waterline, water will rush into your boat at a rate of 88 gallons per minute (over 5300 gallons per hour!). Compare this sample failure to the rate at which your bilge pumps work. If there is a big difference, consider upgrading your existing bilge pump system in order to be able to handle an emergency situation:

Many boats have inexpensive "ribbed" hose that creates friction and back-pressure on the bilge pump. Replacing this ribbed hose with smooth-bore hose will result in increased pumping action.
Upgrade the wiring to the bilge pump to reduce voltage drop to 3% or less. Use this voltage drop calculator under the Technical Info pick on this website to determine the proper size wire for the "round trip" from battery to pump and back.
Install a larger capacity pump. You'll also see significant gains in pumping capability when you move from smaller pumps with 3/4" outlet hoses to larger pumps with 1 1/8" outlets.
Install a second float-switch in the bilge that will sound a loud alarm when the water is 3" or 4" above the normal height.
Install a separate shower sump. If you have a shower that drains directly into the bilge, consider installing a separate shower sump and pump. The hair that washes down the shower drain will quickly clog even a large bilge pump and cause it to fail.

Manual Bilge Pumps

There's an old saying that "the best bilge pump is a scared sailor with a bucket. All boats should carry at least one bucket and a simple, sturdy manual bilge pump. These pumps will keep working when electric pumps fail.

Maintenance and Clog Prevention

Here are a few tips for making sure that your bilge pumps will work when you need them most:

Keep your bilge clean of debris. Rinse it out thoroughly twice a season.
Clear out the "limber holes" that let water flow between bilge compartments.
Make sure bilge pump wires are not sitting in standing water. Wires will quickly corrode if they are in water.

Dewatering Equipment - Inshore Sailing

	Item	Link to Detail
Automatic Pumps
	Electric bilge pump of sufficient capacity to clear the bilge in a reasonable time
	Smooth bore hose with no check valves or other obstructions. Anti-siphon loop extends above the waterline when the boat is heeled.
	High-water alarm in bilge - set for 6" above bilge pump trigger level (optional)
	Wired directly to batteries through a circuit breaker; won't turn off when you turn off your master battery switch
Manual Pumps
	Bucket (at least one, two are better)
	Manual bilge pump (permanent mount)
	High capacity emergency manual pump (optional - good idea if you're sailing in areas where help may be slow in coming)

Links to Outside Resources

	Item	Link to Detail
How-to Articles
	How to install a bilge pump system; different types of bilge pumps.	Link
	Test reports: 20 different bilge pumps compared	Link
	Basics of Installing a bilge pump from BOAT/US	Link

Manufacturers
	Wave-driven bilge pump - no electricity needed - for small boats	Link

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