One essential element before you head out to sea, whether you’re a boat owner, passenger or traveller, whether your trip is short or long, is water. Obviously, humans require water to live and that salty sailing water isn’t going to cut it.
Some yachts and motor cruisers have larger freshwater tanks that may be sufficient for a few days away. With many yacht designs opting for more storage space over water capacity, boat owners are choosing a watermaker to supplement their requirements and allow them to stay out for longer. A watermaker is a device that produces fresh potable drinking water out of seawater through a process called reverse osmosis.
We’ll go through the differences, pros and cons between portable and installed watermakers - everything from cost, size and storage to operation and maintenance. By the end, you’ll know which is right for you. We’ve compared the Rainman portable unit and Schenker’s Energy Recovery Zen Watermaker units as examples.
Watermakers come in a variety of shapes and sizes, usually measured in litres they produce per hour. For most boats with 1-4 passengers, a watermaker of 30 to 70 L/h is usually sufficient, but if you’re operating a larger yacht or motor cruiser with more persons on board, you may need something larger or opt for a smaller, quieter watermaker & run it for longer when you need more water. Another consideration is how and where to store your watermaker, again, this may depend on the size of your vessel. A lot of smaller vessels are limited in space and this can impact the type of watermaker you go for. Rainman offers a petrol-operated, two-piece watermaker unit that’s portable & operates right from your deck allowing you to take it on different boats or even bring it ashore if you go adventuring.
Alternatively, there’s the Schenker Watermakers, sold exclusively by SWS Pacific. They have impressively compact ZEN models starting at 19kg, which are super easy to install either horizontally or vertically. By installing, you don’t need to worry about hauling an entire system out onto your deck for each use or messing around with dropping hoses - an installed watermaker is also easier to use while you’re underway. The Schenker watermakers accommodate large vessels with their Modular Reverse Osmosis Watermaker range, going all the way up to a 500 litres per hour
Operation & Power
The big decision is whether you are happy with hauling the portable watermaker out of a locker and setting it up on the deck every time you want to make water. Or do you just want to push a button on a remote control panel?
The Rainman portable electric watermaker weighs in at around 24kg for the pump unit plus the reverse osmosis pack starting at 11kg plus the hoses for seawater suction, brine and potable water into your freshwater tank. All this needs to be lifted onto the deck and set up before use. Power consumption is around 1250W so you’ll either require a generator or a large battery bank with a suitable inverter to run the unit. Alternatively, you can have the Raiman in a petrol version that is slightly heavier again and you’ll need to keep petrol on board to operate the unit. Operation is quite simple once you’ve connected the hoses, just turn the unit on and wind the regulating valve in until the desired pressure is reached. When you’ve finished filling your tanks, you’ll need to flush the reverse osmosis membranes. If seawater is left in the reverse osmosis membranes, the organic material in the seawater will die, rot and smell. This will eventually damage the reverse osmosis membranes. Flushing the Rainman portable unit is achieved by filling a clean bucket with water produced by the watermaker and then placing the watermaker suction hose into the bucket so that the clean water is pumped through the membranes. The flushing process should be repeated every week if not using the watermaker or you can add a biocide to the flushing water for longer-term storage.
The compact Zen Watermaker unit is relatively simple to install and the components allow for easy positioning in yachts and motor cruisers where available space is at a premium. Once installed, water is produced by simply pressing the start button on the small remote control panel. There’s also no need to wind valves as the Energy Recovery System self regulates the pressure in the system. The unit can also be set to run for timed operation or water tank level control. When the unit stops, it automatically flushes to protect the membranes. The unit can also be set to self-flush weekly if you’re not going to be aboard. With the low power consumption of only 110W, there’s no requirement for a generator and it is happy running on the smallest of battery banks.
Both Rainman’s portable units and Schenker’s Zen range of watermakers have similar maintenance requirements. Both have a course seawater strainer filter to stop larger debris from entering the pump. Both units have 5-micron cartridge filters to protect the reverse osmosis membranes that will require changing from time to time depending on the turbidity of the seawater. Both units, if operated correctly, should give a membrane life of around 5 years or more.
On top of that, additional maintenance specific to the Rainman includes a lift pump impellor and high-pressure pump oil that will require changing annually. The high-pressure pump will also require overhauling periodically.
The Zen has a small carbon filter on the membrane flushing side to change every 6 months. This removes any chlorine that may be in the water to protect the reverse osmosis membrane. The internal seals of the new Zen units are made with special friction bands resulting in years of trouble-free operation. The feed pump head will require replacing over time.
Many people get out onto the water just to relax. You don’t want to disturb that tranquillity with a hulking, loud watermaker right? Unfortunately, there’s no escaping the noise from a Rainman portable watermaker when it's operating on the deck of a yacht. You may choose therefore to install a Schenker watermaker with its quiet and patented Energy Recovery System.
The decision usually is going to come down to cost versus convenience.
A Rainman portable petrol-driven kit ranges from AUD8,200 to 9,500. The electric version ranges from AUD6,300 to 7,500. If you’re going to go electric portable you’re also going to have to consider if you’re going to require a generator or larger battery-bank and inverter system.
Schenker’s Zen range starts at around AUD9,000 but you’ll have water at the touch of a button and full automation. From there though, maintenance costs are relatively low, especially if you’ll use it regularly. Watermakers thrive when used frequently so do consider this when opting for portable or installed.
The bottom line is that both of these watermakers will do the job, but which is best suited for you? When you next sail out on the high seas, which will you go for?