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Creating clean
drinking water on your boat and while cruising is a necessity. Water tanks
can only hold so much water and restricted space onboard may preclude you
from carrying enough water for your needs. Whether you have enough capacity
for all your water needs or not, having a marine watermaker can make planning a
long distance cruise easier. Wouldn't it be great if you
could add more drinking water to your tanks at the flip of a switch. Well
you can but there are many things you should know about yacht and offshore marine
watermakers. They are
complex in installation and maintenance. However if you learn the basics you
can easily keep your marine water maker producing your water requirements.
Watermakers use Reverse Osmosis to make water. This is the opposite
process of osmosis that plants use. Wiki
definition of Reverse Osmosis and description below; Reverse osmosis (RO)
is a separation process that uses pressure to force a
solvent
through a
membrane that retains the
solute on one side and allows the pure
solvent
to pass to the other side. The membranes used for
reverse osmosis have a dense barrier layer in the polymer matrix where most
separation occurs. In most cases the membrane is designed to allow only
water to pass through this dense layer while preventing the passage of
solutes (such as salt ions). This process requires that a
high pressure be exerted on the high concentration side of the membrane,
usually 2 to17
bar
30 to 250
psi, for fresh and brackish water, and 40 to 70 bar 600 to 1000 psi, for
seawater, which has around 24 bar 350 psi, natural osmotic pressure which
must be overcome. Although Reverse Osmosis
seems like a complex system it is really a simple and straightforward water
filtration process. High-pressure (pump driven) reverse osmosis systems have
been used for years to desalinate water to convert brackish or sea
water to drinking water Katadyn Swiss portable
watermakers, this one is recommended for
liferafts. Also look at their low power consumption and 12V power
watermakers.
Spectra
Newport watermaker Schematic
1;
Thru hull It appears plunger pumps are popular for
watermakers. Spectra and SeaRecovery
use these type of pumps. Spectra uses a CAT pump Other features include,
Automatic pressure adjustment which allows for variation in salinity and
temperature of the sea water. How much water are you going to need, what size watermaker do you need?
One
example I can tell you about
watermakers and maintenance involves Chessie Racing during the
1997-1998 Whitbread round the world Yacht Race. Due to saving weight and
space requirement there is a lot of emphasis on
watermakers for essential
water supplies on these 60 ft race boats.
The race starts in England and the
boats sail around the world anticlockwise sailing into the southern ocean
before sailing back into the Atlantic and then back to the UK. It was in the
southern ocean that Chessie ran into watermaker issues. They had many spare parts but
still the watermaker failed. They even had backup PUR hand pumps and for a
week of sailing that's all the water they had. They eventually had to plan a
pit stop to get more spare parts and the nearest point of land was Ushuaia
Argentina the most southern city in the world. they had their shore crew
meet them with more spare parts and they were quickly back in business and
on their way. It was an important lesson in having enough spare parts but
most importantly the fact they had hand pump backups as this fact saved
their lives as they were over 1,000 miles from land when the issue surfaced. This picture is of New Zealand
Atlantic rowers who used the Katadyn Power Survivor as their water supply
plus backup air guitar.
Katadyn powersurvivor 80
E watermaker for sale
First check
your manufacturers maintenance requirements. The diagram above shows the
parts in the system, All these need to be checked but the filters in
particular are most important. Clogged filters and a dirty membrane will
make for poor and low production. Filters Regularly check
the sea water strainer and the two particle filters Membrane
Watermakers like to run often even daily for a couple of hours. Running
the watermaker like this coupled with automatic back flush, which takes the
minerals salt etc off the membrane surface, keeps the membrane clean and in
good working order. A membrane not cleaned in a
week can get bacterial fouling. If you do not use the watermaker in a week
you should flush the system or put it into storage mode which involves
pickling. Membranes should not be stored dry. Membrane Flushing Some systems have an automatic
flush system built in, other smaller units require manual flushing. Some
systems may have a separate tank for water for flushing. Manual flushing of the membrane
requires switching the valves on either side of the membrane, the
inlet side and the discharge side, and then turning the unit on to circulate
clean water. Many larger systems have an
auto flush mode. This can save lots of time and convenience. Flushing water needs to be free
of chlorine and so a carbon filter is recommended between the tank
containing the flushing water and the membrane. Chlorine can react with some
cleaning chemicals. The membranes should be permanently immersed in liquid:
either sea water before treatment, fresh water provisionally stored or
sterilizing liquid if the water maker is not used for extended periods of
time Pickling involves special biocides which are mixed with the product
water and pumped into the system leaving the membrane saturated. Use the
manufacturers recommended biocide. The membranes should not be exposed to temperatures
freezing. Overpressure due to expansion caused by freezing can rupture the
membranes and prevent the salt from being filtered out. The membranes must
not be exposed to temperatures above 60°C as high temperatures may also
prevent salt from being removed. Watermakers are
not recommended for use in muddy or polluted water as the pre filters get
clogged and damage the membranes. If you do use the watermaker in these
waters only run it for very short periods: as soon as clean sea water
becomes available clean the membranes and run the system without pressure
for 30 minutes with the pressure regulator open. Spare parts Carry plenty of spare filters.
Filters last 6 months after first use. Also carry spare parts for pumps etc
especially if you are going to be away from land or good stores. This
article from Crew-Life.com is from a professional who describes the
watermaker system and how he uses it on a boat.
You have fresh water, what no,
what do you mean no? Clean Water from the membrane goes into the water tank
however there maybe contaminants in the tank and between the tank and
faucets, for your newly fresh water. If you want to build your own
watermaker you can read this report where
the builder paid around $2,000 instead of closer to $8,000 for a bought one. Read part 2 of the making fresh
water series to find out how to keep water fresh and soft.
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