Whether you’re crossing an ocean or day-tripping through the islands, the crew will need water to drink and, hopefully, for more than the occasional shower. With a fuel-efficient passagemaker and a large fuel tank, it is more likely that running out of fresh water, not fuel, will bring a boat back to the dock—unless you can make your own fresh water with a watermaker.
HOW IT WORKS
In its most basic sense, a watermaker uses a high-pressure pump to push seawater through a filter called a membrane. All watermakers have membranes, which are installed in sealed, pressure-rated tubes. The membranes have pores small enough to keep out salt and other contaminants, while still allowing fresh water through. This sheeted material is wound spirally around a permeate tube. As salt water is pushed through each layer of the membrane, it is progressively filtered until it is pure, fresh water.
Watermakers typically utilize a low-pressure pump to prime the high-pressure pump that then pushes the water into the membrane at around 800 psi. This process is called reverse osmosis. Osmosis is how plants and trees move liquid and nutrients up their stalks. In this process, a
