When we dream of casting off for good, we often think of downwind conditions, exotic ports of call, the peaceful lapping of deserted anchorages... But soon enough, a very concrete question comes to mind: what about fresh water?
On ocean-going cruisers, this resource, so commonplace on land, becomes a daily challenge. A tap isn't enough: you have to plan, store, ration or produce. This is where the watermaker comes into play. Long reserved for top-of-the-range sailboats, they now appeal to a growing number of independent sailors in search of freedom.
But before you buy, it's best to know your needs, your technical constraints and the solutions available. Here's a pragmatic overview of what you need to know to choose and maintain this sometimes life-saving, sometimes temperamental, always precious equipment.
Why install a watermaker on board?
When you live aboard for several weeks or months, fresh water becomes a strategic issue. Even as a couple, consumption rises quickly: daily showers, washing up, rinsing, laundry... And in tropical zones, the heat makes consumption even higher.
The watermaker brings a certain comfort: no need to run after water points, nor to store dozens of cans. You gain in autonomy, freedom and serenity, especially in archipelagos where water is scarce, expensive or of poor quality.
How does it work? Reverse osmosis basics
A watermaker extracts freshwater from seawater using a semi-permeable membrane and high pressure (55 to 70 bar). The water is first pre-filtered (to retain sand, micro-algae, etc.), then sent under pressure through a membrane. The result is two streams:
- fresh water (permeate)
- salt-concentrated water (discharged into the sea)
The system consumes energy to create pressure and requires regular rinsing (maintenance) to preserve the membrane. It generally produces between 30 and 150 liters/hour of fresh water, depending on the model.
Which type to choose? Power, energy and size
Here are the main types of watermakers, with their characteristics:
| Type | Flow (L/h) | Power supply | Consumption | Average weight | Dimensions |
| 12V (compact) | 30-40 L/h | ~15-20 Ah/h | ~25-35 kg | Small bunker | |
| 220V or motor | 60-150 L/h | Generator / motor socket | ~500-1000 W | ~50-70 kg | 2 compartments min. |
| Hybrid / solar | Variable | Optimized | Variable | Often modular |
Installation: You will need :
- a dry, ventilated and easily accessible space (avoid the engine hold if possible)
- a dedicated seawater intake
- saltwater discharge (a T on an existing discharge is sufficient)
- a fresh water supply to the reservoir or an independent tap
Weight and bulk are rarely insignificant: a watermaker weighs between 25 and 70 kg, divided between high-pressure pump, filters, membrane and controllers.
Installation and maintenance: what we don't always tell you
Installation is do-it-yourself with good plumbing/electrical skills, but requires method and rigor. The classic mistake: underestimating space or neglecting accessibility for maintenance.
Don't forget :
- Regular filter changes (pre-filtration, etc.)
- Rinse with fresh water after each season to prevent crystallization
- Long-term storage (if not used for a long time) with biocide solution
- Regular checking of pressure switches, leaks, flow rate
Certain breakdowns are common in tropical zones: beware of heat, humidity and the quality of the power supply.
What's your budget?
| Element | Estimated cost |
| Compact 12V device | 3 000 âeuros 5 000 ⬠|
| Watermaker 220V / high flow | 7 000 âeuros 30 000 ⬠|
| Installation (pro) | 500 âeuros 2 000 ⬠|
| Annual maintenance | 300 âeuros 1000 ⬠|
The purchase may seem expensive, but in the long term, especially if you avoid marinas and sail far away, the "return on comfort" is undeniable.
Advantages, limitations and alternatives
Benefits :
- Free access to water wherever you are
- Comfortable living on board
- Autonomy for long voyages or isolated anchorages
Disadvantages :
- Energy dependency
- Mandatory maintenance
- High initial cost
Alternatives :
- Regular provisioning + strict management
- Rainwater harvesting (DIY or buy-your-own systems)
- Limiting consumption
To conclude
A watermaker is not essential for every sailing project, but for a long and autonomous life on board, it quickly becomes a strategic investment. It's best to choose it carefully, install it properly and take good care of it.
" Being autonomous also means anticipating your needs and making the right choices in advance. "
