Water Maker Info

Ian Shepherd <g4ljf@...>

As promised, here is the word on Dessalator water makers. It comes via their
UK agent who met with Patrick, the number two at Dessalator last weekend. I
was hoping to forward an email from them, but to date it has not arrived.

Firstly our water makers are designed, built and installed with the salinity
probe functional. The diverter valve will only send the water to the
freshwater tank after the 2 minute timer has completed it's cycle and the
salinity probe detects that there is a low enough salt content. The reason
why my short circuit test of the probe did nothing is that in order to
prevent erosion of salinity tester probes, the polarity in reversed some 500
times per second. Short circuiting does not simulate salty water. I guess
the only way to test it would be to cap the probe hole and dunk the probe in
a cup full of salt water.

If at any time the salinity probe detects salt, the unit does not shut down,
but diverts the water overboard. The green 'water good' LED will also change

Patrick also said that membrane perforation is very unlikely, the more
common problem being that the membranes clog up, causing reduced output. It
is possible that an O seal will fail or that a membrane end cap might split.
However, if this happens, the salinity probe will detect bad water and
immediately operate the diverter valve to send the bad water over the side.
The symptoms of a perforated membrane would be an increased flow rate above
normal and a low pressure indication.

So in a nutshell, we have nothing to be concerned with. Our Dessalator water
makers are perfectly safe and should a membrane failure occur, they will
fail to a safe condition.

In our conversation, one interesting point was raised. I don't know about
you, but when I am using the washing machine, I do try and use the gen set
to advantage by also running the water maker to replace the water used.
Unfortunately, I cannot run my 160 l/h unit at more than about 80 l/h, else
the gen set trips. Does anyone else find this happens? Maybe I have a slack
circuit breaker on the Onan. It should trip at 30 amps AC.

Patrick says that to run the water maker out of the green range is not good
practice. The reason is that the membranes are constructed by rolling up the
material like a roll of wall paper. In order for the membranes to achieve a
perfect seal, they need to be under pressure, else sea water can work its
way from the centre of the roll to the outside, maybe at concentrations just
below the salinity probe detecting unsafe water. It will be OK but not taste
quite so good.

I hope this clears up once and for all any doubts about our equipment, which
I have always found to be excellent. The latest models have an automatic
back flush, which may be beneficial if you don't use your water maker
regularly. M. Wagner says that it is only necessary to back flush if you are
not using the system for a period of 10 days or so, but automatic flushing
might improve the taste and prolong the membrane life if you forget.

I have an inquiry out to see if the modification to an automatic back flush
is feasible on our circuit boards, and at what cost. I will post the answer.

Fair Winds

Ian Shepherd SM 414 'Crusader'

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