What Is a Water Ballast Sailboat?

Water Ballast Sailboat

Sailboats have many components that provide stability, including a water ballast. They need these components, otherwise the boat would risk tipping over (also known as capsizing) if the winds got too rough. Does your sailboat have a water ballast? How does it work? We did lots of research to provide you the answer. 

What is a water ballast sailboat? A water ballast sailboat is one with a water ballast built in. This ballast pushes the water towards the boat’s hull, using the natural forces of gravity to boost your boat’s stability. The water ballasts are part of a bigger system that includes pumps and tanks. 

If you’re thinking of getting a sailboat with a water ballast system, then you’re not going to want to miss this informative article. In it, we’ll explain more about how these systems work and how to fill your own ballast tanks. We’ll even go over the pros and cons of water ballast sailboats. Keep reading! 

How Does a Water Ballast System Work for Sailboats?

Before we go deeper into what a water ballast system is and how it works, we need to explain ballasts in general. Found on ships, sailboats, and other vessels, a ballast keeps the hull’s lateral forces in check. Without this, the boat becomes much more likely to lean or heel when in the water and faced with strong winds. Leaning too much to one side could cause the boat to capsize, which occurs when the sailboat falls over.  

While there are both live ballasts and high-density ballasts, the one we’ll focus on for this article is the water ballast. Sailboats and other smaller vessels tend to come outfitted with this ballast type. 

A water ballast gets installed in such a way that its vertical center of gravity makes the boat more stable. This means the hull gets covered in water for the system to be effective. The ballast itself can cut into the waterline with no detriment to the stability of your sailboat. It is called a water ballast, after all. 

Today’s sailboats will typically come with their own water ballast systems, including internal tanks. These sailboats are made for recreational purposes like cruising or racing. The positioning of the internal tanks allows for no risk of decreased performance in downwind or upwind sailing. That said, to maintain this careful balance, it’s important to ensure the ballast tanks are mostly empty if riding downwind but full when sailing upwind.  

How to Fill the Ballast Tanks

Like we just touched on, depending on the direction you’re traveling in your sailboat (upwind or downwind), you’ll have to learn to fill and empty your ballast tanks. Since they’re part of a water ballast system, it makes sense these tanks would be filled with water. 

Where can you find your water ballast tanks? How much should you fill or drain them when boating? Let’s answer those questions now.

So, Where can you find your water ballast tanks?

While it can depend on the model of sailboat you own, you should find your water ballast system near the boat’s hull. Remember, the ballast may sit lower, closer to the waterline. As mentioned, the tanks are often internal, so they shouldn’t take away from the silhouette of your sailboat by adding a clunky profile. That’s not true of every sailboat, though. 

Again, while it varies, some sailboats have switches for maintaining ballast tank fullness. These may include on and off switches as well as an empty switch. When you want to fill the tank, you’d press the on switch. As the water nears the top of the tank, you’d hit the off switch.

How much should you fill or drain the ballast tanks when boating?

Certain sailboats will come with water ballast tank systems that turn off on their own when they fill completely with water. Not all tanks will do this, so it’s important you read through your owner’s manual carefully to see what your water ballast system is capable of. If your tank system doesn’t power itself down, then you can keep going and going and accidentally overfill the tank. Water will begin traveling where you don’t want it. 

How does pressing a switch get the water to the ballast tanks?

Sailboats come equipped with what’s called a ballast pump. This transports the water to the tank so you don’t have to do so manually.

Other sailboat models use ballast bags, and some boats have both tanks and bags. If your boat includes ballast bags, you have to fill these yourself. To do so, you want to lay the bag on a flat surface. Then, take your fill connection and attach it to your fill port. You’ll find this port on the ballast bag, typically towards the top.

When both sides of the tube are tightened, take your ballast pump and let it go into the water. Make sure it’s not floating, as you want it deep. Next, grab the extension cord that comes with your ballast pump, connecting it to your boat’s cigarette adapter. If you don’t have one of these adapters in your boat, you can always fill the ballast bags in your car before hitting the water. 

Double-check you don’t have too much air in the ballast bag, as otherwise a lot of water will come with it. Then, you’re done!

To release all the air from the ballast bags, connect your ballast pump to the included field drain. Then, position your hose so the water will pour out of the boat rather than inside it. 

Here is a handy YouTube video that shows how it’s all done.

The Pros and Cons of a Water Ballast System for Sailboats

By this point, you know a lot about a sailboat’s water ballast system. If you have a different kind of ballast for your boat, you may wonder if there’s a reason to make the switch to a water ballast system. 

Indeed, these systems have a slew of advantages, but downsides exist as well. Let’s go over both more now. 


  • Besides stability, a sailboat with a water ballast system may achieve greater speeds than one without. By lessening heel angle, the sails, rudder, and keel of the sailboat maintain their lift and profile, staying horizontal. This means downward sail pressure is reduced, allowing for greater speed. 
  • You can also gain better control of the boat by filling your ballast tanks with water. For instance, you’ll notice more handling of the draft, trim, and steering. 
  • You can change the weight of your boat on-the-go by managing the water ballast tanks, as explained above. Given that it’s not too difficult to add or drain water to the tanks, you can quickly achieve the perfect weigh onboard your sailboat with a bit of practice. 


  • The water ballast system sometimes does detract from the overall look of the sailboat. While it’s true the ballast is very functional, some people might see its components as an eyesore. 
  • The tanks can be quite bulky and heavy as well. 
  • They’re also space hogs, thus motivating some sailboat manufacturers to use ballast bags instead of ballast tanks. These bags get installed near the hull and are outboard for easy access. 

There are of course environmental concerns to talk about, too. After all, boats can take water for the ballast tanks in one body of water and then move elsewhere to drain the tanks. This may release foreign microorganisms, viruses, small animals, and plants into another body of water in which they don’t belong. In turn, this can harm the ecosystem.

While this is a very real problem, it’s much more common for bigger boasts like bulk cargo carriers, sizable tankers, and cruise ships instead of sailboats. Still, with the U.S. Coast Guard and the Environmental Protection Agency (EPA) managing what gets dumped and where, it’s best you tread carefully about where you fill and dump your ballast tanks. 

Related Questions 

How can valved pipes be used with a water ballast sailboat system?

Many boaters that have water ballasts use a valved pipe to connect the starboard and link port tanks. You would open the valve on the pipe and let water pass through the windward or upward tank. This is positioned higher than the valve, letting water move. An included sheet contains the water so it doesn’t travel too much and cause the sailboat to heel.

As the water moves to the leeward or downward side, the boat sail sheets. This raises your upward tank, transferring the water back. If it doesn’t all move, then use a hand pump for transferring it. 

Why do sailboats need ballasts?

As we said in the article, sailboats with water ballasts tend to have greater stability. Through adjusting the water levels in the ballast tank, it’s also possible to increase the speed of your boat. 

Does a sailboat need a keel?

Yes, absolutely. A keel serves a very important role on your sailboat, maintaining the ballast weight. This works against the wind force that could knock your sailboat over into the water. Keels also create lift thanks to their airfoil wing shape. This allows you to sail nearer the wind than you could with keels of a different shape.  Click here to read more on keels.


I am the owner of sailoradvice. I live in Birmingham, UK and love to sail with my wife and three boys throughout the year.

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