“... The first question to ask before the installation of a Watermaker should be: How do I drive my high-pressure pump? AC, DC or belt? ...”
Are you AC, DC or belt? ~ as published in “Caribbean Compass”
Since the revolutionary development of the first Reverse Osmosis
membranes by DuPont some 40 years ago millions of tons of potable water
have been produced from salt water
by RO desalination plants. They have saved lives, made the desert fertile and even produce the water
necessary for the ice rink to get the Saudi royalty skating.
Some of the smaller units have reached such a degree of reliability
and affordability that more and more yacht owners cruising the seven seas consider a watermaker
the best option to provide themselves with the priceless commodity 'fresh water'.
All watermakers available for yachts follow the same reverse osmosis
principle, where highly pressurized seawater flows along a rolled up, semi permeable membrane, which allows a certain amount of freshwater to pass. This freshwater is collected and directed into the tanks
, while the rest of the seawater flows back into the sea as brine.
The first question to ask before the installation
of a watermaker
should be: How do I drive my high-pressure pump? AC, DC or belt?
AC driven systems make perfect sense if you have a sizeable generator
of five KW or more. Various manufacturers offer a multitude of models. Be aware that electronics
in combination with watermakers have a tendency to create problems, which normally cannot be fixed without spending a lot of money
and the help of a manufacturer approved service
station. One drop of saltwater in the wrong place is all it needs to get you carrying jerry cans again. A non-computerized version costs less to begin with and is much more reliable.
belt driven systems can produce huge amounts of fresh water even on a smaller yacht without a generator
and without putting any extra strain on your battery
system. Their only disadvantage is that they are not so easy to install and sometimes there is just not enough space around the engine
to accommodate the really quite small pump unit. Once in place though they are pure joy, especially if they are equipped with an automatic regulating valve. This will grant a constant pressure regardless of the engine RPMs, thus adding safety
, ease of operation and longevity.
12 or 24 Volt DC systems are the most versatile, as batteries can be charged by alternators, generators, solar panels
, wind-, water- or shaft generators or shore power
. There are two versions on the market:
1) systems with energy-recovery, its commonly known representatives being Spectra, Schenker, Katadyn
Power Survivor (PUR) and Livol and
2) systems without energy recovery like the ECHO Tec, HRO, Sea Recovery
or the Village Marine
Both approaches have their advantages.
Some Energy-Recovery systems use only 60% of the amps to produce a given amount of water, therefore putting less strain on your energy budget
. The Spectra Catalina
300 for example, claiming to be the most energy efficient watermaker in the world, produces 12.5 gallons of freshwater using 15 Amps @ 12 Volt. A breakthrough compared to older systems like the Katadyn/PUR.
So why buy a system without energy-recovery and use more Amps? Lots of reasons again! Modular versions like the EchoTec200 or the Little Wonder cost some $2,000.00 less to start with. They are also easier to install, cheaper to maintain, more robust and longer lasting. Depending on how many hours a day you run them, a small solar
panel or a stronger alternator
takes care of the difference in consumption
Once you have decided on the power supply, the number of showers and washing
machines on board has to be discussed with admiral and crew. Typically AC and belt driven units produce between 20 to 60 gallons per hour, while 12 Volt units are limited at a maximum of 17 gallons per hour.
Make sure that all wetted metal components of your watermaker of choice including the high pressure pump are made of high quality stainless steel
and you should be good to go and enjoy sailing wherever safe water supply is an issue.
Anyway the times are over where a watermaker was a pure survival instrument, luxury is on!