Why Do Boats Spit Out Water? 6 Quick Answers (For Beginners)

You might have noticed that boats can be seen spitting out water. You might also wonder why this is.

Why Do Boats Spit Out Water?

Boats typically spit out water to keep the bilge free of water. Water builds up over time inside the bilge and the bilge pump automatically pumps the water out again. Often, when boats are spitting out water, it is because they are expelling water that has built up in the bilge of the ship.

What Is The Bilge Of A Boat?

bilge water pumped out of the side of a ship in the water of the port

The bilge is the lowest compartment in a ship that sits below the waterline. This bilge is where the two sides of the ship meet underwater at the keel.

The term bilge can also be used to describe the water that collects in the bilge of the boat. This term is used because of the condition of the water that collects in the bilge.

With other contaminants present in the bilge water, it is often smelly.

How Does Water Get Into the Bilge of a Boat?

The bilge often collects water that does not drain off the side of the boat’s deck, or through a thru-hull.

Common causes of water collection in the bilge are:

  • Rough seas
  • Wave spray
  • Melting ice
  • Leaks in the hull
  • Leaks in the stuffing box
  • Other interior spillages

It is important for the water collected in the bilge to be pumped out. If this water is not properly dealt with, the bilge can become too full and possibly cause the vessel to sink.

Bilgewater is something that can be found on most types of vessels.

Bilgewater is not just water. Depending on the boat, its design, and its function, bilge water can contain:

  • Oil
  • Detergents
  • Solvents
  • Chemicals
  • Other materials

Because bilge water has other components, it should be monitored, and it is possible that discharging bilge water can be restricted for certain vessels.

Why Do Boats Have Bilge Pumps?

A bilge pump is a water pump that is used to help remove or pump out bilge water. Bilge pumps are set to pump out water when the bilge is full up to a certain level.

These pumps are used instead of manual bilge water removal tactics such as using buckets to remove the water.

Electric Bilge Pumps:

Modern bilge pumps are often electric and can be controlled by automated switches.

These switches are necessary when the water collected in the bilge gets to be too high.

There are two common types of electric bilge pumps. These two types are centrifugal and diaphragm pumps.


Centrifugal bilge pumps draw in water using spinning vanes that then push the water out through an outlet port.

For these pumps to work, they must be submerged in the bilge water to operate.

These pumps remove all but the last inch or so of water.

These pumps also generally have a built-in strainer that can be easily removed for cleaning.


These pumps use a membrane to lift water into the intake hose and then expel the water into the outlet hose where it discharges outside the hull.

These pumps also have a strainer to keep out clogs and to assist in cleaning.

Overloaded Bilge Pumps:

Bilgewater often collects gradually, but if there is damage in the hull or the bilge, it can collect much quicker.

Bilge pumps are not ideal for use if you have a major intrusion of water. Large amounts of water can overwhelm your pump system.

If you have a known leak or break in your hull, you should not rely solely on your bilge pump to resolve the issue.

Decontaminating your Bilge:

Besides bilge pumps, there are also other methods to help with bilge water maintenance.

As mentioned above, bilge water can contain other contaminants that can make it unsafe to dump into the water.

You can use bioremediation to help make your bilge water more harmless to the environment. Bioremediation uses bacteria to break down the hydrocarbons in the bilge water to create harmless byproducts.

This gives the bilge water a more environmentally friendly impact. This is because it does not introduce hydrocarbons directly into the water.

Tips To Know About Bilge Pumps

There are some tips that will help when dealing with your bilge and bilge pump.

These tips include:

  • Do not allow large amounts of water to build up in your bilge. This can destabilize your vessel and can affect balance, performance, and buoyancy.
  • Bilge pumps cannot handle major leaks so if your boat has one you should immediately take care of it.
  • Before you set out on your boat, you should vent the bilge for five minutes. This can dissipate potentially combustible fuel fumes.
  • Before you get underway, muck out the bilge and clean the pump strainer.
  • Vent the bilge for five minutes after fueling.
  • Larger boats are much more susceptible to shipping water. For this reason, sailboats often have more than one bilge pump, so if you use a boat with more than one bilge pump it is important that you know how they operate.
  • If you check the bilge, make sure you look or smell for fuel that might be present. If there is any, make sure you follow safety and environmental guidelines to remove the fuel before you get underway.

Do All Boats Have Drain Plugs?

A drain plug is a plug that is located at the bottom of your boat’s transom. When you remove this plug, water drains out.

If you replace it, it prevents water from coming back in.

It is highly important that you remember to drain the water from your boat and then put the plug back in while your boat is on land.

This step should be completed every time that you intend to launch your boat.

Drain plugs can be easy to lose but also very inexpensive. You should always have a few on hand just in case and your boat should never be launched if the drain plug is not properly reapplied.

Drain plugs are highly important for boats that are not “self-bailing”. However, not every boat has a drain plug. Boats that do not have a bilge pump are often the smaller ones that will have a drain plug. Most boats have at least one of these options.

Drain plugs allow all the water to exit a boat, while bilge pumps only drain most of the water. This is not ideal for boats that are stored during the winter.

Any boat that will be stored for several months during the winter requires a drain plug so the water can be properly drained.

If there is water in the boat when it is stored for winter, the freezing temperatures can affect the water and do damage to the boat.

There are exceptions, however, such as pontoon boats. Due to the design and layout, this is not something that you are likely to see on a pontoon since water doesn’t have the same opportunity to collect.

Why Do Tugboats Shoot Water?

Tugboats are boats that serve the main purpose of assisting other vessels in maneuvering when they are unable to do so themselves.

However, this is not their only function.

Due to their powerful size and strong build tugboats can be used to:

  • Assist in the movement of other vessels
  • Serve as icebreaking boats
  • Serve as salvage boats
  • Firefighting boats
  • Entertainment or ceremonial vessels

Tugboats are often seen shooting water. This can serve a few purposes.

Some tugboats are equipped with high-pressure water guns that assist in the dousing of fires. They can be seen shooting water out of these multiple nozzles.

Some tugboats that are equipped with these nozzles also use them ceremoniously to welcome boats in and out of a harbor or for other special occasions.

Tugboats can even be seen performing a ballet in Hamburg Harbour.

Final Thoughts:

Boats can be seen spitting out water in multiple ways. Mostly, this is a safety feature.

While manufacturing does everything within its power to make a vessel waterproof, it is highly unrealistic that boats are completely resistant to water getting into places it shouldn’t.

Even a boat with no hull damage or other sources of damage can take water into the bilge. This can be from rough water, waves, or other water that drains from the vessel.

Even a boat sitting on a trailer in the driveway can take on water if it rains. For this reason, you should have a bilge pump or drain hole and plug.

These devices allow you to remove the water that collects in the bilge and can help maintain stability and the integrity of your vessel while out on the water.

Make sure you follow the proper draining and safety techniques whether you have a drain plug, bilge pump, multiple bilge pumps, or all of the above.

You should maintain and empty your bilge properly for the safety of you and your passengers as well as for the safety and preservation of the environment.

If your hull does, in fact, have damage, you will want to get that fixed immediately. You will also want to avoid taking your vessel out on the water until the damage is fully dealt with.

If you follow the proper guidelines and precautions, you can have both a safe and relaxing boating experience, even if water occasionally spits out of the boat.

Was this article helpful? Like Dislike

Click to share...

Did you find wrong information or was something missing?
We would love to hear your thoughts! (PS: We read ALL feedback)