When we purchased our first full-time cruising and liveaboard, a Lagoon 380 catamaran, we set out with the same list of outfitting and equipment questions that most new boaters do. Although we had been boaters for years prior, we were new to big liveaboard appliances like generators, air conditioning, and watermakers.
Independence was a blank slate; she had none of those options. That’s mostly what attracted us to her: the fact that she was cheaper than boats that had these options. It was also appealing to minimize maintenance and keep operating costs down.
A few years later, we sold Independence and bought Dulcinea, our 35-year-old cutter. Dulcinea didn’t have these pieces of equipment, either. But we were determined to have some, as we’d learned our lesson in some areas. Now we’ve been aboard for 5 years, and guess what? There’s even more I’ve learned and even more I’d do differently.
Here’s the first in a series of articles: My thoughts on watermakers for boats.
What Are Watermakers on Boats?
A watermaker is a machine that turns seawater into pure drinking water. It sounds like a dream come true, and obviously, you must have one of these magic machines on your boat, right?
But watermakers come with a slew of issues. For one, they’re expensive. In parts alone, you’re looking at somewhere between $4,000 and $8,000. That’s for a small unit on a typical cruising boat, 30 to 60 feet long. Bigger units for bigger boats cost more.
Purchasing a watermaker is only the first part of the equation. Installing it is a major plumbing project. You’ll need an underwater through-hull for the inlet, which means the boat must be hauled out of the water. That’s at least $1,000 right there, so obviously, you’d want to combine this with other projects. Then, the system needs to be plumbed into the boat’s freshwater system. If you’re paying someone, it’s easy to spend as much on the installation as you did on the watermaker. That pushes the cost up to the $10,000 to $15,000 range.
Maintenance and upkeep are also issues. All watermakers have some type of pump, and pumps eventually go bad. The reverse osmosis membranes can theoretically last many years, but they will foul if you don’t use them regularly and treat them right. There are also pre-filters, which strain out muck and algae, that must be replaced much more often.
How Do Watermakers Work?
Watermakers work thanks to the power of reverse osmosis (RO) membranes. These are basically super filters that prevent anything other than pure water from passing through. To get them to work, the water must be supplied at very high pressure, usually 800 PSI. No matter what brand watermaker you buy, nearly all of them use DOW FilmTec membranes, the industry standard.
To get the seawater up to 800 PSI, you’ll need a plentiful supply of water feeding a very powerful pump. At its core, this part of the watermaker system is just like a garden-variety pressure washer. Plug your garden hose in, turn on the pump, and out comes a blast of high-pressure water. In fact, there are plenty of DIY watermaker plans available online that use off-the-shelf pressure washer parts.
Types of Watermakers on the Market Today
Boats have multiple power sources, so there are a variety of types of watermakers available. Getting water up to 800 PSI takes a lot of energy, so it’s important to find the solution that works for your boat. There are only three ways to run it on a boat: 12/24-volt DC, 120/240-volt AC, or engine-driven.
Engine-driven systems are mostly phased out now since boats either have gensets or solar to run an appliance like this. A few companies make gas-powered watermakers, like the Rainman gas portable unit. This isn’t a viable solution on a boat, however. It’s more intended to be taken to remote locations and used on land where there’s no other power source available.
If your boat has a genset, the obvious choice is a 120/240-volt system. They use a lot of power, 1,000 to 1,500 watts, but they also make a lot of water, 25 to 40 gallons per hour. With a genset, you could run this all day. It can be done with a portable gas generator, like a Honda 2200, but that means you need to carry gas and a generator to make water.
The 12/24-volt DC systems come in two flavors, and this is where it gets tricky. When I started researching, I failed to really understand the difference between the two.
The typical 12-volt system, like the ones sold by Rainman or Seawater Pro, are high-wattage, high-pressure pumps that are simply 12-volt equivalents of the 120/240-volt systems. In other words, they still consume 1,000 watts or more to make water. That will drain a small cruising boat’s battery bank very quickly and is far more than solar can recoup effectively. There are also the installation requirements—it’s basically the size and power of another electric windlass. 2 AWG or 4 AWG wires are expensive!
Then there are 12-volt systems like those made by Spectra, Schenker, Electromaxx, and a few others. These systems use a recovery or Clark-style pump to build up the water pressure. The recovery pump is mechanical, using hydraulics to build up the water pressure to feed the reverse osmosis membrane. The only power required to operate them is for the feed pump, which is a typical continuous-duty diaphragm water pump, much like your freshwater system uses. Total energy required: 100 to 200 watts. Some systems use more than one of these pumps, but it’s still a fraction of the power that a high-wattage pump uses. The trade-off is that these systems make less water, usually 7 to 20 gallons per hour.
The fact that these systems make less water is actually a plus. It means that you’ll use it more often, which is the best situtaiton for a watermaker. The thing that kills them is sitting, and if you turn it on for a little bit every few days, it will last forever.
In addition to the type of power input, you can also choose between portable and installed units. With a portable, you have the advantage that you could sell it or take it with you when you sell the boat, thereby allowing you to recoup some of your investment cost. But portable units are a major hassle—more on that in a minute.
Why Are Watermakers So Expensive?
I’ve explained how a watermaker works in a few paragraphs. Most of the parts are nothing special. The magical DOW membranes can be purchased for less than $300 apiece. So why are watermakers more than $5,000?
There are many reasons. The pumps used are very expensive, be it the Clark recovery pump for a Spectra or a high-pressure pump for a 120/240-volt system. These are generally all stainless and cost well over $1,000 for the pump alone.
There’s also the packaging and convenience. Watermakers come with all the parts, ready to be installed. You don’t need to be an expert at watermakers to make it all work—someone did the thinking for you. And, of course, tech support, parts, and warranty are nice things to have when you shell out this much money for something.
You can do it yourself for less money, but doing so requires a high level of knowledge of how watermakers work. You’ll also need to find all the little fittings, pipes, and parts to make it work in your boat.
What We Did and What We’d Do Differently
When we bought Independence, we opted for a Rainman portable 120-volt model paired with a Honda 2000-watt gas generator. I would never do that again.
My problems with this system:
- Noise—the Honda generator is relatively quiet compared to the Rainman pump
- Weight—the pump unit weighed 60+ pounds, and the membranes weighed another bulky 30 pounds or so. Getting it in and out of boat-sized compartments sucks.
- Storing it took up a huge amount of space.
- Setting it up was a pain.
- I would love to get rid of the Honda generator
We kept the Rainman on Dulcinea, but we installed it permanently into the boat. This was the choice because we already owned it and it was basically free at this point. It’s all far to heavy and large for our boat.
If we were starting again, I’d do a Spectra or similar-style 12-volt system with a recovery pump. This could be run easily off our 12-volt system anytime…while motoring, on days with plenty of solar, or while plugged into shore power (or the Honda portable generator). That’s the sort of flexibility we need aboard our small boat, and the 120-volt Rainman limits us to using it while running the Honda generator. It’s conceivable that if we didn’t have the Rainman anymore, we might not need the generator at all.
Side note: I had thought that running the 120-volt system off our inverter would be possible. We have a 2,000-watt Victron inverter, but found that it overheats after about 20 minutes of running the Rainman (about 1,200 watts). That issue could likely be fixed, but our inverter is too valuable for us to take the risk of putting it under undue stress.
Do You Even Need a Watermaker?
All of this begs the question: Couldn’t we just do without the watermaker? They are, without a doubt, luxury items that are not entirely necessary for cruising. Many, many people cruise without them.
But they are oh, so handy and nice to have. The Bahamas are often mentioned for East Coast cruisers since this is the first location where many folks are made to pay for fresh water. The cost isn’t a lot, $0.20 to $0.50 per gallon in most places, but I think it’s a mental block for many sailors.
The bigger problem we’ve had is controlling the quality of the water in our tanks. We have a watermaker but hate using it (see the reasons listed above). We often fill up at fuel docks or marina faucets, sometimes using jerry cans. Over our travels, we’ve become acutely aware that marinas have some of the dirtiest water available. Many, especially in remote areas of Chesapeake Bay, are on wells that aren’t providing potable water, strictly speaking. Even if the water could be potable, the management at the marinas does not keep the systems flushed and clean, so winding up with nasty bacteria in your tanks is much easier than you’d think. In many cases, the locals all consume bottled water, and it’s beyond belief to the management that anyone would think about drinking it.
To mitigate all these problems, we’ve developed a number of procedures to keep our tanks clean and sterilize the water. We also have an Acuva UV light filtering system that should keep any harmful bacteria at bay. We chlorinate our water anytime we take on new water. And we shock chlorinate our tanks and water lines occasionally. Finally, we’ve stopped taking on water from shady-looking hoses or marinas and opted to use the hated watermaker more often. After all this, our absolute favorite way to get water is by collecting rain.
What do you think? Are watermakers must-have items on your boat? Had you considered that finding good, clean drinking water in the US would be a problem before you set out?
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