When it comes to watermakers picking the best for you is crucial with a key decision being the type you go for an its energy usage.
Watermakers – technically known as desalination units – use a process called reverse osmosis (RO) to make drinking water. By forcing salty water at a high pressure against one side of an RO membrane, fresh water will slowly seep through, leaving the salt and bacteria behind. The output is notably devoid of minerals, but the taste can be a little strange at first.
There are two main types of watermaker. High-pressure pump watermakers are fast, but they aren’t the most energy- efficient way of creating clean water. They are usually tuned to produce 60 litres per hour or more but can draw upwards of 500W and while there are 12V versions, they typically use mains voltage pumps and are better suited to being run from a generator than a battery bank.
They’re designed to fill your tanks quickly so you don’t have to run the generator for long. Mechanically, they’re simple, and apart from the high-pressure pump there are no moving parts to go wrong.
The alternative method is a Clark pump watermaker, also known as an energy recovery device (ERD). This uses a fast-running but much lower-pressure pump which needs less power. To obtain the high pressure required, the pressure in the discharge water is harnessed by a couple of reciprocating pistons and used to boost the inlet pressure. It takes a few minutes to build up pressure and during that time the output is slow and not very clean.
Best watermaker: ERD units
Schenker Zen 30
I’ve yet to meet the owner of a Schenker Zen 30 who isn’t an evangelist for this machine. The Italian brand has been evolving its range since 1998 and offers a three-year warranty. Measure twice – the pump and membrane make up a bulky unit.
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I love the design of the Osmosea units, which only have one moving part and are one of the cheapest ERD units out there, although reliability is poor, due to the materials used. Cheap second-hand ones are often available, so worth considering if you don’t mind doing a bit of engineering.
While not flawless, this has one of the best build qualities. You’ll find dealers in remote locations, but expect a hefty bill for parts and labour.
It’s a modular design which makes installation easier, but while none of the modules are huge, there are a lot of modules.
Best watermaker: High pressure units
SeaWater Pro grew out of a garage project using a pump from a Karcher K4 power washer and a garden hose timing unit, but they’ve come a long way since then.
Their latest units now use stainless steel pumps which, unlike Karcher pumps, are designed specifically to propel saltwater.
French brand Dessalator uses beautifully over-engineered pumps with a simple user interface control. Despite being a high-pressure system, they offer a couple of 12V versions, the smallest drawing around 30A and rated at 30 litres/hour. They are very pricey, but the only running costs for years will be pre-filters.
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