How to Carry Drinking Water on a Sailboat
On land, water simply comes out of the tap. On a sailboat, every liter has to be carried, stored, kept clean and rationed until the next fill-up. For a day sail that hardly matters, but for a long weekend, a coastal cruise or an ocean passage, planning your drinking water is one of the most important parts of preparing the boat.
Quick answer: most cruising sailboats carry their drinking water in built-in tanks, backed up by a few jerry cans and some bottled water as an emergency reserve. Plan on at least 3 liters (about 3/4 gallon) of drinking water per person per day in warm weather, and roughly a gallon (4 liters) per person per day for drinking and cooking on passages, plus a reserve that is kept separate from the main tank. Boats that cruise remotely or cross oceans often add a watermaker.
How Much Drinking Water Do You Need?
Your body’s needs come first. Health authorities generally suggest around 2 to 2.5 liters of total fluid a day for an adult in a temperate climate, and that rises quickly with heat, wind, sun and physical work, all of which come with sailing. Seasickness also increases fluid loss. A simple check: pale yellow urine means you are drinking enough; dark urine means drink more.
Then add water for cooking, a small amount for brushing teeth, and some for washing. Here is a practical planning guide per person per day:
| Use | Planning figure per person per day |
|---|---|
| Drinking (temperate) | 2 to 3 liters (about 1/2 to 3/4 gallon) |
| Drinking (hot or tropical) | 3 to 4 liters or more |
| Cooking and hot drinks | About 1 liter |
| Teeth, light washing | 1 to 2 liters with care |
| Showers and dishes (fresh water only) | Highly variable; can easily be 10+ liters |
| Emergency reserve | At least 2 to 3 liters per person per day of the planned passage, kept separate |
With careful habits (salt-water dishes and washing, freshwater rinses only), many offshore crews manage on 4 to 6 liters (1 to 1.5 gallons) per person per day in total. Our guide to sailboat water tank size works through the numbers for different boats and crew sizes.
A quick example
Two people on a 10-day passage, planning 5 liters each per day, need 100 liters (about 26 gallons) of fresh water, plus a separate reserve of, say, 40 to 60 liters. Add a margin for delays, because passages often take longer than planned.
Ways to Carry Drinking Water on a Sailboat
| Method | Pros | Cons | Best for |
|---|---|---|---|
| Built-in tanks | Large capacity, low and central, plumbed to taps | One contamination problem affects all of it | Every cruising boat |
| Jerry cans | Cheap, flexible, separate reserve, portable for shore runs | Take up space; must be stowed securely | Reserve and refills by dinghy |
| Bottled water | Known quality, easy to grab | Bulky, plastic waste, cost adds up | Emergency stock, day sailing |
| Flexible bladder tanks | Add capacity in odd spaces | Chafe risk; must be secured | Boosting capacity before a passage |
| Watermaker | Makes water from the sea; less hauling | Cost, power, maintenance | Remote cruising and ocean crossings |
Built-in water tanks
Built-in tanks are the backbone of the system. Many boats have two or more tanks, and that is a real advantage: if one gets contaminated or a fill-up was doubtful, you still have clean water in the other. Use one tank at a time, and keep a log of when and where each was filled. Tank water is safe to drink when it is kept clean and turned over regularly. See our article on is boat water tank water safe to drink for details, and our step-by-step guide on how to clean a boat water tank for the annual sanitizing routine.
Jerry cans
A few rigid 10 to 20 liter (2.5 to 5 gallon) jerry cans give you a separate reserve and an easy way to ferry water from shore by dinghy when you are at anchor. Use cans made for drinking water, label them clearly (blue is common for water), and never use cans that once held fuel. Keep them out of direct sun, which warms the water and encourages algae, and lash them down so they can’t move in a seaway. A full 20-liter can weighs about 20 kg (44 lb), so they should go low and close to the middle of the boat.
Bottled water
Bottled water is the easiest way to know exactly what you are drinking, and a stock of it makes a good emergency reserve, part of the grab-bag water if you need to abandon ship. As a main supply, it is bulky, heavy to carry back to the boat, expensive over time and creates a lot of plastic waste. Most long-term cruisers use bottled water for backup and filter their tank water for daily drinking.
Flexible bladder tanks
Collapsible bladders can add capacity under a berth or in a locker before a long passage. Use only drinking-water-rated bladders, pad any sharp edges, and strap them down so they can’t shift; a loose bladder full of water is heavy and can chafe through.
Watermakers
A reverse-osmosis watermaker pushes seawater through a membrane at high pressure, producing fresh water and discharging brine overboard. It frees you from hunting for dock water and lets you cruise remote areas for longer. The trade-offs are cost, power (most run on 12 or 24 volts from the batteries, or on AC from a generator, or are driven by the engine) and maintenance: a watermaker needs regular use or proper pickling, clean pre-filters, and it should not be run in harbors or polluted water. Treat it as a supplement to your tanks, not a replacement; you still need a reserve if it breaks down mid-ocean.
Where to Stow Water Aboard
Water is heavy: a liter weighs a kilogram, and a gallon weighs a little over 8 pounds. A boat carrying 400 liters of water is carrying 400 kg (880 lb) that affects its trim and stability.
- Keep it low and central. Stow jerry cans and bottles in the bilge or under the cabin sole, as close to the middle of the boat as you can.
- Keep it out of the ends. Weight in the bow or stern makes the boat pitch more and sail less well.
- Balance it. Spread water evenly from side to side, or use it from the windward tank to help trim on long passages.
- Secure everything. In a knockdown, loose water containers become dangerous projectiles.
- Keep it dark and cool. Heat and light encourage algae and spoil the taste.
Our tips for efficient storage on a sailboat can help you find space for reserve water without cluttering the cabin.
Getting Water Aboard Safely
- Fill from taps marked as drinking water, and ask the marina if you are unsure.
- Use your own drinking-water-rated hose and let the tap run before filling.
- Use an inline hose filter to keep sediment out of the tank.
- Treat water from doubtful sources, or keep it in a separate tank for washing.
- Divert the first runoff when collecting rainwater, then filter and disinfect it before drinking.
If you want an extra safeguard, a drinking-water filter at the galley tap or a portable filter for jerry cans and shore water is a good investment. Our guide to the best portable water filters for boats explains what each type removes.
Water-Saving Habits That Make Your Supply Last
- Wash dishes in seawater and rinse sparingly in fresh water. A saltwater foot pump at the galley sink makes this easy.
- Swim or wash in the sea and use fresh water only for a final rinse.
- Brush your teeth with a cup of water instead of a running tap.
- Cook pasta and potatoes in a mix of seawater and fresh water (clean offshore seawater only, never in harbors).
- Fit a foot or hand pump on the galley tap, or switch off the pressure pump on passages, so nobody leaves a tap running.
- Keep track of what you use each day so you know how many days of water you have left.
Staying Hydrated on the Water
Carrying water is pointless if the crew doesn’t drink it. On deck, wind and sun make it easy to underestimate how much you lose. Give each crew member a refillable bottle with their name on it and keep it within reach in the cockpit. On hot days or during hard work, add electrolytes. Dehydration causes fatigue, headaches and poor decisions, which is why it shows up among the most common sailing injuries and accidents. See also our list of the best food to bring on a sailing trip for provisioning ideas.
Summary
The best way to carry drinking water on a sailboat is to combine several methods: clean built-in tanks as the main supply, jerry cans and some bottled water as a separate reserve, and a filter at the tap. Plan at least 3 liters of drinking water per person per day in warm weather, about a gallon per person per day for drinking and cooking on passages, and a reserve on top of that. Stow water low and central, keep it clean, use seawater wherever you can, and consider a watermaker if you cruise remote areas or cross oceans.
