9 Dec 2005
Hi Eric and others:
On our recent sail from Portsmouth, Virginia to Bermuda and then the
BVI we had an interesting water maker failure.
I had purchased a Total Dissolved Solids (TDS) meter to monitor the
water output of my 120 liter 220 VAC Dessalator water maker. It had
been consistently putting out water with about 350 ppm (parts per
million) of TDS water. This is evidently well within the normal
limits for our water makers. Tap water tended to be 500 to 600 ppm
even after we ran it through the carbon filters we always use to put
dockside water in the tank. I had noticed after running the water
maker once that the TDS raised from 350 ppm to about 900 ppm coming
out of the tap. This puzzled me so I purchased and installed a "Y"
valve for the product water line. I plumbed this into the product
water line just where it dumps into the fresh water tanks. Initially
the water maker was putting out 350 ppm water at this point and we
continued to have good quality water for several days. Then one day,
about half way through our passage, I drew a glass of water from the
filtered water tap and it tasted salty. I measured the TDS and it
was about 4,000 ppm. I fired up the water maker and with the green
light on, and the system producing water I tested the direct output
of the water maker, sure enough the product water was measuring about
9,000 ppm. The water maker failed to divert bad water and
contaminated our entire water supply.
I emailed Dessalator and inquired about trouble-shooting. They
suggested that I individually test each membrane by disconnecting the
gray plastic fittings at the end of each membrane. This I did, and
both membranes were putting out bad water. Meanwhile the green light
remained on and the in line sensor appeared normal. I am not sure
what happened but it appears that my diverting system isn't working
correctly and my membranes are shot. We finished the last three days
of our passage with emergency water supplies, juices and soda pop.
My emergency hand pump RO water maker produced 1 quart of water per 1
hour of pumping. You sweat almost as much water as you pumped.
I am in the process of replacing the membranes,(Dow company FilmTec
2540SW, 2.5 inch by 40 inch sea water FilmTec membranes about $700
USD each), and end caps and seals from Dessalator for $640 USD).
Dessaltor says the system should divert at 1,000 microSiemens
conductivity. They state that the normal output should be between
600 to 700 microSiemens. 1,000 microSiemens equates roughly to
1,000 ohms of resistance or about 480 ppm of NaCL. I don't have a
direct conversion to TDS ppm. I plan to conduct further testing once
my system is re-plumbed.
Here are my observations about ensuring longevity of the water maker,
for what they are worth:
1. PICKLING: I will try to never pickle my system again. I will
hire someone to fresh water flush the system every week or plumb an
automatic fresh water flush. The Sodium MetaBisulfite pickling
solution is corrosive to the seals on the pumps and end caps and also
to the metal pump shafts etc. If I absolutely must pickle I will use
the absolute minimum concentration of bisulfite. I had been somewhat
cavalier about the amount of pickling agent I used in my 5 gallon
bucket of pickling water.
I inquired from Dessalator about their automatic fresh water flush
system. It is my understanding that retrofit is possible (expensive)
and that the fresh water flush from Dessalator only activates a flush
cycle upon system shut down. It has no provision, as far as I can
determine, to flush on a weekly basis while the boat is un-attended
2. CHLORINE: I have installed an in line carbon block filter in
the fresh water flush line so that all water going through the
membranes will have passed through a carbon filter.
While I had always been careful to charcoal filter dockside water I
had sanitized the water system with chlorine. After sanitizing I had
pumped the tank dry and flushed the entire system again with chlorine
free water but perhaps there was enough residual chlorine on the
surface of the tank to have damaged my membranes. I will purchase a
chlorine meter and monitor chlorine levels in the flush water and
water from dockside.
3. BRACKISH WATER: I had used the water maker in the Chesapeake
Bay for several months, (brackish water). I had never exceeded 120
l/min of production but even so brackish water is evidently not good
for the water maker. I won't use the water maker in brackish water
4. CARFUL MONITORING: I will measure TDS, Conductivity, and
Chlorine levels with religious zeal.
5. PERIODIC TEST THE CONDUCTIVITY SENSOR AND BYPASS SOLENOID
FUNCTIONALITY. I plan to use a spare Dessalator conductivity probe,
attach the wires from the control unit via a switch so that I
can "sense" some sea water at the flick of switch and test the bypass
circuitry and solenoid to verify that they are activating correctly.
6. CARRY MORE EMERGENCY WATER IN JERRY CANS ON LONG PASSAGES.
Just my thoughts. By the way my water maker only had 185 hours of
use on it over 4 years with periods of pickling lasting up to 6
I welcome any thoughts from other owners.
Regards, Gary Silver
Amel SM 2000 Hull # 335 Liahona lying Sea Cow Bay, Tortoal,