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From: (no name) (no email)
Date: Thu Sep 09 2004 - 23:04:12 EDT
In a message dated 9/7/2004 10:18:45 AM Eastern Daylight Time,
writes:
Norm:
Now that you've had it for a while, what are your impressions of the Spectra
water maker? Do you like it? Does it produce anywhere near the rated
capacity? Just wondering . . .
Chip Wilson
s/y 'Ajax'
Fort Myers Beach, FL
Spectra is very proud of their gear so I bought only the low pressure pump,
the high pressure Clarke Pump and the pulsation damper from a Spectra dealer in
New York. I got the membrane and housing from SK Watermakers, the prefilter
housings from Home Depot, the prefilters from Farm Tek Supply, stainless
gauges from a local auto supply and a high powered low pressure pump from Depco in
St Pete FL.
The membrane and housing are a standard 40" type. These membranes are
standard, common, and available from any RO dealer. This keeps the price down.
This is the opposite from my Village Marine Tech unit that takes an odd size
membrane available only from Village Marine Tech at "you pay our price or throw
away your watermaker" prices.
The high pressure "Clarke Pump" is unique. It is actually a pressure booster
that takes the low pressure water at around 100 psi and boosts it to several
hundred psi for the membranes. I have had no problems with it yet but
seawater dribbling from its control valve is corroding the base plate, a job on list
#2.
I hooked up both small and large low pressure pumps in parallel. The circuit
was: sea valve, sea strainer, both low pressure pumps in parallel, 20 micron
filter, 5 micron filter, pulsation damper, Clarke Pump, membrane, overboard
sea valve. There are some valves and gauges also.
I could choose which low pressure pump to be used with switches. They both
had check valves on their outputs.
At first the system performed as advertised, but within a few days the output
fell rapidly to less than 5 gph.
The small low pressure pump, which came with the Clarke Pump, failed early
on. First the high pressure limit switch failed so I bypassed it. Then it
started leaking, so I removed it. Then the pump output fell to unusable levels.
The dealer I got it from in NY refused to sell me any parts and told me
(apparently I was talking to the "boss") that he would not have sold me the gear in
the first place. He did not say why and I did not ask but my guess is that he
would realize a much greater profit if he had sold me a complete system. I
have not used that pump since.
The large low pressure pump I bought from Depco after carefully examining the
one offered by Spectra and I believe I have substantially the same pump for
$250 less than Spectra's price. This pump is an Italian rotary vane type pump
with graphite interior and built-in relief valve. Both pumps have 12 VDC
motors. It worked well at first producing 18 gph, but it too gradually failed
until I was getting less than 5 gph of product.
After examining the entire situation I concluded that the high silt level of
seawater in St Augustine was the culprit that destroyed both pumps by abrasion.
The Depco pump was sent to Depco for rebuild, thence to the distributor in CT
and they replaced the interior parts "gratis". They agreed that the abrasion
of the silt probably killed the pump. However, only the soft interior parts
needed replacement and they were relatively inexpensive. I could order the
parts and replace them easily myself.
When I got the pump back I rebuilt the system but this time with the two
filters upstream of the Depco pump to protect it from silt. I had to add yet
another pump upstream of the filters, between the sea strainer and the filters, to
push the water through the filters to feed the Depco pump. This is a Flo-Jet
type general purpose pump.
This setup works well now, putting out 14 gph of product.
But I am in the relatively clean water of New England and do not know how it
will stand up to the heavy silt of St Augustine.
As things stand now, this system is not safe for unattended operation because
there is no auto shutdown for the system if the feed water pressure to the
Depco pump should fall below zero due to fouling of the filters and cause
cavitation of the Depco pump. Cavitation of this pump is not a Good Thing and I
would need to rig some sort of auto shut down. When I am on board now, I can
hear it complain and shut it down. I also would like another gauge showing the
Clarke Pump's feed water pressure and maybe the RO membrane feed water
pressure.
I would also like to rig (I have all the parts, just haven't had the time...)
a diverter valve and timer to dump the first three minutes of product (it is
salty at first) so that, with the anti cavitation shutdown system, the rig is
capable of fully automatic operation. I could then hook it to the Trace
inverter, which has three programmable voltage (12 VDC) sensitive relays I could
set to turn on the RO when the batteries are fully charged by the solar panels
and wind generators.
So far the system works, producing 14 gph of good fresh water but at a cost
of 30 amps.
Perhaps with more reengineering I could get the efficiency up. Spectra
claims one amp hour per gallon, and this is probably possible with a small low
pressure pump in clean seawater in the original configuration. But like many
advertised specs, it has not worked out this way in the real world for me.
Norm
S/V Bandersnatch
Lying Gloucester MA
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