What is Desalinators or Watermakers?
Marine watermakers turn seawater into fresh drinking water using reverse osmosis. Seawater is pumped at very high pressure through semi-permeable membranes that remove salt and minerals.
Answered by Marine Keeper — the boat maintenance platform trusted by boat owners and charter operators to track, schedule, and understand every system on the water.
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What it is
Marine watermakers turn seawater into fresh drinking water using reverse osmosis. Seawater is pumped at very high pressure through semi-permeable membranes that remove salt and minerals. Complete systems include a raw water intake with strainer, pre-filters, high-pressure pump, RO membrane housings and pressure vessels, product water storage, brine discharge overboard, and a control panel. Many modern systems feature automatic freshwater flush cycles to protect membranes during storage and extend their service life.
What it does
Watermakers provide fresh water independence, eliminating the need for shore water, rationing, or searching for sources when cruising remote areas. They produce high-quality drinking water from seawater, allowing generous use for showers, laundry, and cleaning that would be impossible with limited tankage. Many systems monitor water quality to ensure safety. By providing reliable freshwater, watermakers enable extended offshore passages and remote anchorage stays, greatly increasing cruising range, comfort, and convenience.
Why it matters
When a watermaker fails, crews must ration limited tank water, reducing showers, preventing laundry, and creating uncomfortable living conditions, especially in hot climates. Extended remote cruising becomes impractical, as routes must be planned around freshwater availability rather than weather or destinations, limiting flexibility and comfort.
General Maintenance
Run the watermaker at least once a week if you are not producing water regularly to prevent biofouling of the membranes. Replace pre-filters every 100–300 hours of operation or whenever the pressure drop exceeds the manufacturer’s specifications. If the system will be idle for more than 5–7 days, pickle the membranes with a biocide solution to prevent microbial growth. Check the raw water strainer daily during operation and clean it as needed. Monitor product water quality using a TDS meter, readings above 300–500 ppm can indicate membrane problems. Service the high-pressure pump annually, including seal replacement. Descale membranes annually, or sooner if production drops or pressure requirements increase, signaling mineral buildup. Inspect all hoses and fittings regularly, especially high-pressure lines, for leaks. Replace membranes every 3–7 years depending on water quality and maintenance history. Keep spare pre-filters and membrane pickling supplies on board for extended cruising. Always check your watermaker’s owner’s manual and follow the manufacturer’s recommended service intervals before performing any maintenance.
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