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Old 19-09-2010, 17:37   #166
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Apart from customising an installation to suit your boat, is there a big saving to be made in building yourself?? I thought the cost was mostly the filter/membrane system.
And just how long do you get out of a membrane before it has to be replaced???
I do not know what the parts add up to now a days - but I do know the prices of complete R.O. units from the major manufacturers has gone up in price from 3x to 4x the price I paid 8 years ago. They are now considered a must have piece of equipment on modern cruising boats instead of a novelty nearly a decade ago so the prices have gone up as demand has increased.

That makes D-I-Y units attractive.
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Old 19-09-2010, 17:44   #167
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As I understand it, the problem with the 4" units is flow. You have to have sufficient flow to the units for them to function correctly and too little flow can ruin them. Flow = larger pump = greater power requirements. If you've got the power to produce the flow then I think 4" is the way to go.

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Old 19-09-2010, 17:52   #168
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I was at the Newport Boat show Friday. I was awed with watermaker prices! A 400 g/day unit if I remember correctly was around $8-10K!!! Sure, they had SS and one had titanium for the head. But this is just over design. Those materials are in the category of using nickel for hub caps.

Yes! Those are quality materials but are they needed? The material cost plus machining cost drive their product cost. I am no authority on brass but from what I have read and what I believe, there is just no solid, rational reason to over design one of these things.

Wait awhile, the Chinese might recognize a business area anxious for cost reduction. Next we might see quality watermakers coming from China at a much lower cost.

But hey, I just wanted to build my own.

Foggy
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Old 21-09-2010, 13:08   #169
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I know there are several Internet books you can buy on how to build your own watermaker. There are even a few interesting plans for free. I would never in any way discourage anyone from attempting a DIY unit. But I wonder if there would be much interest in a small book on the many mistakes and pitfalls, (many of which I see in this thread), of taking on a DIY water maker before you start buying parts? I have seen a few good ones and have seen some pretty nasty Rube Goldberg disasters. I tell me wife more often than she cares to hear. "I could write a book"
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Old 21-09-2010, 13:15   #170
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Wait awhile, the Chinese might recognize a business area anxious for cost reduction. Next we might see quality watermakers coming from China at a much lower cost.

But hey, I just wanted to build my own.

Foggy
I have yet to see anything of quality come from china. Im certainly sure I wouldnt want to cross an ocean with a chinese watermaker as my only source or supply
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Old 21-09-2010, 15:26   #171
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I know there are several Internet books you can buy on how to build your own watermaker. . . .
Why buy a book? The ones I have seen in stores are normally a decade or two or more behind the times. The technology changes a lot in that amount of time.
- - You can download for free R.O. manuals from most of the manufacturers and just copy what they have done. You can also look at the units at boat shows and see up close and personal what the guts look like.
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Old 21-09-2010, 15:41   #172
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I have seen a few good ones and have seen some pretty nasty Rube Goldberg disasters
Tellie, from what I remember arnt you a travelling Spectra man. Please enligthen us as to the mistakes.

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I have yet to see anything of quality come from china.
you must be living in a cave Anjou, mind you " Malvernshire, on the sunny side of the hill" hmmm.. Most of everything you drive, live in , buy etc has parts made in china, that includes your boat too.. ( like mostof the elctronics for example).!!

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Old 21-09-2010, 15:48   #173
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n my opinion it's not worth bothering with anything other then brass heads because if your treating your watermaker right you're doing plenty of fresh water flushes so the unit will not. Be seeing too much seawater.
BTW when I made that statement, its not neccesarily a reason to use the cheapest pump, There are lots of reason to use a good quality pump, but the head material isnt one of them
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Old 21-09-2010, 16:08   #174
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I have yet to see anything of quality come from china. Im certainly sure I wouldnt want to cross an ocean with a chinese watermaker as my only source or supply
To add to GoBoatingNow's post - If you look at your country's national flags for tourists; the Westminster/et.al. replica plastic stuff, and hundreds if not thousands of all the consumer goods in the "mass discount" markets/warehouse stores you will see "Made in China."
- - Although most of the actual hulls for sailboats/power yachts are still made "locally" as there is not market for a production run of a million units. However, the electrical equipment, instruments, commuications equipment and pumps, etc., etc., are also "Made in China."
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Old 21-09-2010, 17:08   #175
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I have yet to see anything of quality come from china. Im certainly sure I wouldnt want to cross an ocean with a chinese watermaker as my only source or supply
Fifteen or so years ago I decided to design, build and manufacture my own wind generators. The design inluded an aluminum casting that we machined in my basement, special fields wound to my specifications and MAGNETS along with sundry other components.

I needed the most powerful magnet I could get for my design, neodymium-iron-boron. These magnets have field intensity around 12,000 gauss, they to my knowledge are unsurpassed in magnetic field strength.

I searched and searched here in this country for a supplier.....at that time I found NOBODY. I did however find a Chinese company that was able to produce a small quantity for my design inluding holding the mechanical tolerances to +/- 0.001!!! They delivered promptly at a very small cost considering the order size.

You need better information on Chinese products.

OH--- I built 10 units plus one for my sailboat at that time. They functioned just as designed. I did not try to enter a manufacturing phase because I was scared to near death about potential liability suits where someone died because his/her head hit a rotating propeller.

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Old 21-09-2010, 17:14   #176
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As I understand it, the problem with the 4" units is flow. You have to have sufficient flow to the units for them to function correctly and too little flow can ruin them. Flow = larger pump = greater power requirements. If you've got the power to produce the flow then I think 4" is the way to go.

Thomas
I AGREE! Good post Thomas! Somehow I thought "geez, that is for me! One membrane, less plumbing, consider the benefits!" Later I started to consider why I planned to use two 2.4X40 membranes in series rather than parallel. Immediately I remembered why!!

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Old 28-09-2010, 13:09   #177
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The flow is a direct function of the RPM. I could be wrong on this, but I believe the pressure will be whatever it needs to be to get the flow. Of course there are limits and I don't knowwhat they are other than calculating what the horsepower is for a combo of flow at a given pressure. It could be that with enough horsepower
at any RPM, the flow could be restricted to cause soaring pressure, enough to damage the pump. Just my thoughts--

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Old 28-09-2010, 14:04   #178
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Put an "unloader" on the pressure side...basically a pressure relief valve...any restriction causing pressures to rise above its set limits allows a dump or "unload" of partial flow...All good pressure washers have them..its what protects the pump when you release the trigger on the gun....they are self resetting and designed to have flow through them pretty much constantly.
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Old 28-09-2010, 14:10   #179
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I have 2 X 2.5inch X 40 inch RO membranes set up in series.

I intend to buy a brass pump pressure washer with a gasoline motor.
These have a high pressure rating of 3,000 psi, they also quote the flow rate but you are never told at what pressure rating that flow is.
With these plunger type pumps does the flow rate vary with the pressure say like on a centrifugal pump or is it fixed.

What flow rate will i need at 800 psi to run my system.

Beau--

Please see post #177. I should have quoted you in it prior to posting

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Old 28-09-2010, 14:17   #180
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Yes that is correct..the piston pumps are all rated at "max" PSI and GPM for their stated operating RPM.


Mine is 1500 PSI @ 4.2 GPM
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