How to Make Water Onboard a Sailboat: Beginner’s Guide to Staying Hydrated at Sea
/Learn how to make water onboard a sailboat using rain catchers and watermakers. Discover essential tips for conserving, storing, and producing fresh water while cruising.
By Michelle Segrest, How to Get Your Sea Legs
Of all the resources you need onboard a sailboat, water is the most precious.
The average human can survive three weeks without food but only about three days without water. That makes fresh water more valuable than fuel, provisions, or even spare sails. Whether you’re cruising for a weekend or embarking on an offshore passage, knowing how to store, conserve, and even make water at sea is a skill every sailor should master.
Understanding Your Onboard Water Needs
Living aboard a sailboat means carefully balancing consumption with supply. At anchor or in a marina, you might use 40 liters a day for drinking, cooking, cleaning, and showers. Offshore, that number drops dramatically—sometimes to just 10 liters a day—because refills aren’t guaranteed.
Reducing usage may mean saltwater dishwashing, quick “bucket showers,” or skipping laundry. On the other hand, adding appliances like washing machines or dishwashers can cause usage to skyrocket.
Most boats carry fresh water in tanks, and the size of those tanks dictates how long you can stay off the dock. For example, a 350-liter capacity might last a week for two sailors under normal use. Once the tanks run low, the big question is: how do you make more water when you’re far from shore?
Refilling Water Options at Sea
1. Collecting Rainwater
The simplest and cheapest way to replenish tanks is with rain. Sailors have been catching water off sails, decks, and biminis for centuries. Authors Lin and Larry Pardey even popularized a rain-catcher setup using hoses from the mainsail or bimini straight into the tank. The obvious downside? It only works when it rains. Depending on your cruising grounds, that can be rare—or plentiful.
Affordable rain catchers make it easy to capture fresh water when it rains.
2. Collapsable Water Storage Jugs
With the portable handle, the collapsible water container is easy to carry. It also can be hung on the mast to release water. When not in use, this water jug is lightweight and can be folded and packed into small space. Equipped with a detachable spout with adjustable water flow, portable water storage containers allow for easy control in dispensing of water. With the 33mm large filling mouth, it also is convenient to fill.
3. Installing a Watermaker
For more independence, many cruisers invest in a watermaker—a desalination device that turns seawater into fresh, drinkable water using reverse osmosis. These systems force seawater through a high-pressure membrane that removes salt, bacteria, and impurities, delivering clean water directly to your tanks.
Watermakers come in engine-driven or electric models, with output rates ranging widely. Some compact units produce 20 gallons (80 liters) per hour, while large “plug-and-play” systems can produce much more. Brands like DOW Filmtec and SeaWaterPro are popular choices among sailors.
Compact units like the SeaWaterPro DIY Kit are budget-friendly, while brands like DOW Filmtec offer higher-capacity options.
Pros and Cons of a Watermaker
Advantages:
Independence from marinas and shore facilities
Ability to anchor longer in remote locations
Freedom to use more water for comfort (e.g., showers, laundry)
Disadvantages:
High upfront cost: $3,000 for DIY kits up to $15,000 for turnkey units
Significant power requirements (AC or DC)
Regular maintenance (changing filters, freshwater flushing, membrane pickling)
If neglected, membranes can fail and the unit becomes useless—a costly mistake.
Regular filter changes are essential to extend system life.
DIY Watermaker Success
One sailing crew installed a SeaWaterPro DIY watermaker when cruising the Mediterranean, where marina water was expensive and scarce. The kit contained common hardware-store parts that could be assembled onboard, avoiding reliance on proprietary technology. This not only cut costs but also ensured they could troubleshoot and replace parts anywhere in the world.
The watermaker became a game-changer. It eliminated the need to plan marina stops, enabled life at anchor indefinitely, and even allowed luxuries like installing a washing machine—a massive upgrade in liveaboard comfort.
Do You Really Need a Watermaker?
Not every sailor does. Many cruisers get by with conservative water use, rain collection, and careful planning. A watermaker is a major investment and requires energy, space, and ongoing attention. But if you dream of remote anchorages, ocean crossings, or living aboard full-time, the freedom it provides can outweigh the cost.
Water is life at sea. Whether you collect rainwater with a simple setup or invest in a high-capacity watermaker, the key is to plan ahead and know your consumption habits. Beginners should start by monitoring daily usage, learning conservation tricks, and exploring refilling options that fit their cruising style and budget.
By understanding how to make water onboard, you’ll sail more confidently, extend your adventures, and enjoy the independence that makes sailing such a rewarding lifestyle.
