SWS Pacific Guest Post – How To Match Your Watermaker To The Size Of Your Boat

Buying a reverse osmosis watermaker is one of the best investments you can make for your yacht and your quality of life on board. Before you jump right into a purchase, however, you need to figure out how much water you need in order to pick the model that is right for you. The size of your boat is often a good indicator of how much water you’ll need, but it will also depend on your individual needs and ideal lifestyle. In this article, we offer some suggestions as to how you can match your watermaker to the size of your boat.

How Much Capacity Do You Have?

Every other decision you make regarding a watermaker depends on the size of your freshwater tanks. A marine watermaker is an important and expensive investment and there is no point in paying thousands of dollars more for a larger capacity model if you won’t gain any additional benefit from it. Similarly, you will be met with major buyer’s remorse if you purchase a system that does not meet your needs and you are forced to ration your water. Figure out your capacity first and the other decisions will become much easier.

sws water maker

How Many People Will Be On Board?
The greatest indicator of your water usage will be how many people are going to be living on board. It is easy to overlook and underestimate how much water you use on land: unless you’re a major miser (in which case owning a boat is definitely not the right decision for you) most people aren’t rushing out to check the water meter every time they turn on the tap.

Between cooking, cleaning, washing and drinking, each passenger requires a significant amount of water, and standard practice is to allow around 30-50L per person per day. With water tanks becoming smaller (most are now between 200L and 500L), four people can deplete their stored water within just a few days and faster if you have freshwater flushing toilets. You can restrict your usage if you so desire but will likely find that it is tiresome and unpleasant having to ration your water constantly. It is far easier just to have a small, quiet, efficient watermaker that you can turn on for a few hours and replenish your tanks while you’re on the move.

Calculate your daily usage to figure out how much production capacity you need. Smaller yachts can get away with smaller watermakers, and we generally recommend the Schenker Zen 30 for vessels with up to four people. The Schenker Zen 50 is suitable for groups of 6-8 people, while the Schenker Zen 100 and 150 are best suited to large vessels or anyone that doesn’t want to worry at all about their water usage. It is also worth factoring in some wiggle room for heavy use days – after all, you don’t want to be the one waiting around in your towel at shower time for the tanks to fill.

schenker water maker

How Much Time And Power Do You Have?
Of course, it is always possible (and tempting) to save some money and opt for a smaller capacity model, however, this comes with a tradeoff in how much time it takes to meet your daily needs. A family of four could certainly get by with a 30L per hour watermaker, but it may require more constant operation compared to a higher capacity model. Conversely, a smaller watermaker like the Schenker Zen 30 may require more time than some of its bigger brothers however this watermaker functions quietly and is low-powered so running it for longer is not a problem.

How much you use your watermaker will be determined by your power source. As more cruisers switch to solar panels and onboard battery storage to supply their energy needs, it is crucial to be mindful of power consumption and how much power will be required for your water production needs.

Spend some time thinking about how you are going to power your watermaker as well as how long you plan to run it. Most cruisers find that running their watermaker for 3-4 hours every day or two is more than enough to keep their tanks comfortably topped up.


Although your water requirements will generally scale with the size of your boat, there is more to the equation than the length of your hull. Your intended lifestyle, number of passengers and available power source will all impact the size and type of watermaker you need, and it is a good idea to gain a strong understanding of how each of these will feed into your final decision.

For more information and advice regarding watermakers, get in touch with the team at SWS Pacific. As specialists in marine desalination, they can help guide you through the process of buying a watermaker and making sure that you have the right equipment for your boat.

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JPK 11.80 July 2024