Watermakers for boats turn seawater fresh.
Freshwater is heavy. At 8.35 pounds per gallon, you don’t want to carry a lot of water while cruising. Once you anchor, the generator is turned on and your onboard watermaker starts making freshwater. The power of having watermakers for boats can be summed up into one word: convenience.
How Watermakers for Boats Work: The Science of Seawater Conversion
Watermakers use pumps, filters, and membranes to purify raw seawater into freshwater. The process, reverse osmosis, is the same desalination plants use on a large scale. At the heart of the process is the membrane, a filter with pores the size of a red blood cell. After the larger particles in seawater are filtered out, the high-pressure pump forces water through the membrane removing almost all the dissolved solids. This method rejects up to 99 percent of salts, contaminates, and pollutants from seawater.
Heat and standing seawater create the ideal environment for biological growth—the bugaboo for watermakers—that can affect water quality. In the past, keeping biologicals from growing involved flushing the system with acidic chemicals. Today, freshwater flushing keeps the membranes clean and greatly reduces maintenance.
Compact and Efficient
“The future of desalination technology is all about being compact and nimble,” says Paul Kamel, product manager of Parker Hannifin’s water purification division. “We can expect to see smaller, more efficient, and more modular designs than ever before. And this isn’t just about saving space, it’s about creating water treatment systems that can handle the most challenging conditions, no matter where they are needed.”
Most boats 40 feet and longer will use watermakers run with AC-powered pumps; however, DC-powered watermakers are used on smaller powerboats and sailboats. AC-powered systems deliver a more constant flow rate and higher pressure over a longer period, while DC systems are for boats with less demand and smaller tanks.
“We introduced the Parker H2O ECO series with automatic operation to improve efficiency, safety, and sustainability with energy-recovery technology,” Kamel says. “The ECO provides up to fourteen point two percent more power efficiency reducing fuel consumption and environmental impact in the way freshwater is produced. It works with AC or DC power and has a small footprint.”
You Get What You Pay For
Watermakers cost between $4,000 and $25,000, depending on the size, output, and complexity. However, consumers often look for the lowest price, a decision that can lead to regret.
“Often customers ask, ‘What is the smallest machine you make?’” says Chip Edmonds, director of sales for Watermakers, Inc., based in Fort Lauderdale. “That’s code for ‘what is the least-expensive machine you make?’ The sad thing is that cost has nothing to do with your freshwater needs.”
For example, Watermakers’ smallest machine makes 10 gallons of water per hour. A 200-gallon tank takes 20 hours to fill, or 20 nonstop hours of running of the machine. The next size up does 20 gallons an hour, yet the price difference is less than $500 more.
“The few times I have not been able to talk someone up to the larger machine, they come back within a month and ask, ‘How do I make more water?’” Edmonds says. “Some people will put themselves in a position where they invested in a watermaker, and they are still conserving water.”
Choosing the Right Watermaker for Your Vessel: What You Need to Know
Edmonds recommends the WMS-1000 for a vessel in the 50-foot range with two to six passengers and also notes the company’s ISL-700 which is a less expensive, no-frills alternative, yet still offers auto-flush. “The auto-flush automatically flushes the membranes and high-pressure pump head after every use and once a week whether the watermaker is used or not,” he says. “This greatly prolongs the membrane and high-pressure pump head’s life.”
Having the ability to choose your level of water purification can make sense for some boat owners. “Vessels that are looking for freshwater stability for an extended time at sea should consider our flagship product, the MaxQ+ APC/DTS with Spot-Free Double-Pass System,” says John Gabriel, director of sales for FCI Watermakers in West Valley City, Utah. “It’s our three-in-one system that allows you to operate in three different modes: seawater to freshwater, seawater to spot-free purified water, and dockside to spot-free purified water. No matter where you are, at the dock or underway, this system allows you to produce fresh, clean water, anywhere.”
There’s no downside to making water faster. Once a sportfishing boat drops anchor and starts fishing, it’s time to make water and ice to keep freshly caught fish cold. For a small sailboat, the quicker you can make water, the less time you need to run a generator.
“I have put watermakers into boats that have only a forty-gallon tank,” Edmonds says. “If the owner goes to a larger machine, it gives them the equivalent of a much larger tank because that can refill it so quickly.
“You are always going to run a watermaker wide open because you have to reach a certain pressure, but with a larger watermaker you can run it less,” he continues. “A rule of thumb regarding the size you need is to buy a machine that can replace a day’s usage in, at the most, eight hours of running time.”
Because of cost and space, having two watermakers isn’t practical for most cruisers. But for larger boats, two watermakers are on board for redundancy. Regarding durability, it’s primarily pumps and motors that are the main issues. Use stainless steel, not bronze or brass pumps, which are going to pit and leak in seawater, and beefier is better.
How Do Watermakers Work?
Boxed or Modular
Consumers can choose from manufacturers who offer either boxed or modular systems. Boxed systems are easier to install and provide a smaller footprint, while modular systems allow the components to be spread out in the engine room. It can be more of a challenge to diagnose an issue in a boxed system.
Finally, there are portable watermakers available, but consider the hassle factors. “Every time you want to make water, you have to lug the system on deck and throw a hose over the side,” Edmonds says. “You can’t make water underway because of the hose, and you don’t have a way to flush the membranes for cleaning. If you have three boats you take out different times I get it, but if you have just one boat, the portable doesn’t make sense.”
-by Doug Thompson