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From: Norm of Bandersnatch (no email)
Date: Thu Aug 17 2006 - 13:32:17 EDT
> i will restate - i suggest you buy individual pumps, filters, membranes,
> etc, and cobble the system up yourself. my local hydraulic shop can make
> any hoses i need with 316 fittings. that's what i would do if i were
> starting over. and buy them from a USA company for ease of shipping etc.
>
get some catalogs and/or instruction manuals to see what you are dealing
with.
a RO is basically a pump that supplies 800 psi seawater to the membranes
and various valves, gauges, prefilters etc to that end.
Essentially, you have a seacock, strainer [strains out fish and vegetable
matter], low pressure [about 15 psi] pump [mine is centrifugal type], a 20
micron filter, a 5 micron filter, [the housings available in home depot and
elsewhere, these are the common under-the-sink units, the pleated filter
elements are around, i get mine by the case from a farm supply], my RO has
a oil/air remover [optional]. this filtered water is fed to the input of
the high pressure pump which is the same sort of three cylinder pump used
in pressure washers, then to the membrane housings which may be several in
series, then to a pressure relief valve you set to 800 or so psi depending
on conditions, then overboard.
the sweet water comes out the product outlets of the membrane housings.
there are desirable accessories.
gauges for feed water pressure [0-15 psi] to the high pressure pump to see
the condition of the prefilters and output pressure [0-1000 psi] of the
feedwater pump to set the proper pressure with the relief valve.
flow meters for the feedwater [0-5 gpm] and for the product output [varies
with capacity of machine].
a way to automatically shut down the system when the feedwater pressure
drops to zero [when the micron prefilters are fouled] to prevent cavation
damage to the high pressure pump. mine is electronic, but some sort of
setable idiot-light switch with a latching relay to control the pump motor
would work. murphy gauge co makes nice gauges with adjustible electrical
contacts that would be very suitable. the sort you would use to keep an eye
on your main engine oil pressure would work nicely.
valves bypass the high pressure relief valve when starting and flushing the
system.
valves to recirculate the seawater when cleaning the system with chemicals
a tds [total dissolved solids - salt level] sensor connected to a dump
solenoid valve to prevent salty water from getting into your tank. the
product water is salty for the first minute or two of operation, then
sweetens up. you could simply wait two minutes or have a two minute timer.
you can buy a hand-held meter to test for saltiness [about $30]
an hour meter to keep tabs on running time is nice.
make everything possible impervious to seawater. that means plastic for
low pressure and 316 or bronze for high pressure. use stainless chassis
and mounting parts whenever possible.
keep electrical devices up high and seawater devices down low. mount pumps
with their motors pointing up and the pump ends pointing down. every
seawater fitting will leak, dribble, or drip eventually and you must keep
seawater away from electrical parts or you will sincererly wish you did.
i would buy the parts and cobble it together myself. 316 fittings and
hoses are available from hydraulic shops. membranes [use only 40 inch
industry standard membranes] and housings are available from various RO
shops. for pumps try Depco in St petersburg. call and ask them for
advice. use only stainless liquid-filled gauges. anything else will need
replacement sooner rather than later. pvc works well in the low pressure
circuits, but use 316 in high pressure circuits. if you find a RO shop you
feel comfortable with you can just buy all the gear from them and they will
advise you too.
i have some of the [expensive] cleaning chemicals but have never found them
to do much of anything. when new, my membranes put out the advertised 25
gph, then slowly sagged over months to 17 gph where they have remained for
years. just plan on having an ouput of 70% of the rated and forget about
cleaning. don't pickle it, just use it at least once a week. at least
that's what i do.
the biggest pain is rinsing the five micron and twenty micron prefilters.
put them where it is easy to spin them off and rinse the pleated filters
with a fresh water hose. how often you will have to do this depends
entirely on the silt in the seawater. for me in key west it was almost
never, in st augustine it was often every twenty minutes.
andina has used a swimming pool sand filter that can be reverse flushed to
help this situation. he gave it to me but i have yet to install it as
other projects lately have been shouting louder for attention.
complexity is harder to cobble up and more expensive but usually works much
better and is more versatile.
any questions?
Norm
S/V Bandersnatch
Lying 30 07.7N 081 39.6W
Julington Creek Estuary FL
> [Original Message]
> From: Mike Stover <>
> To: <>; Ron Rogers <>; Zed
<>
> Cc: A LiveAboardList <>
> Date: 8/16/2006 4:05:01 PM
> Subject: Re: lv-ab: Bandersnatch's Watermaker
>
> Norm,
>
> Do you know of a good design to follow?
>
> Mike
> ----- Original Message -----
> From: "Norm of Bandersnatch" <>
> To: "Ron Rogers" <>; "Zed" <>
> Cc: "A LiveAboardList" <>
> Sent: Wednesday, August 16, 2006 12:06 PM
> Subject: Re: lv-ab: Bandersnatch's Watermaker
>
>
> >
> > i took a look at the companies web site.
> >
> > it is a british company. i have had some english machinery, a mga
> > automobile, and two xk-120 jaguars. i was not impressed with their
> > reliability.
> >
> > as they say, the brits like warm beer because Lucas makes the
> > refrigerators...
> >
> > i will restate - i suggest you buy individual pumps, filters, membranes,
> > etc, and cobble the system up yourself. my local hydraulic shop can
make
> > any hoses i need with 316 fittings. thats what i would do if i were
> > starting over. and buy them from a usa company for ease of shipping
etc.
> >
> > Norm
> > S/V Bandersnatch
> > Lying 30 07.7N 081 39.6W
> > Julington Creek Estuary FL
> >
> >
> >> [Original Message]
> >> From: Ron Rogers <>
> >> To: Zed <>; <>
> >> Cc: A LiveAboardList <>
> >> Date: 8/15/2006 12:34:42 PM
> >> Subject: Re: lv-ab: Bandersnatch's Watermaker
> >>
> >> Norm,
> >>
> >> From the 2004 ARC, the Seafresh H206 watermaker scored best. It was
> >> installed on Oysters and Swans.
> >>
> >> Ron Rogers
> >
> >
> >
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