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Old 08-02-2011, 08:11   #1
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Watermaker Question for the 'Experts'

Hi there

Im am building a fully automatic 40 gph watermaker based on a Wanner D10 pump.

As you know this is a great pump to base a watermaker on . My question is will I need prefilters? This pump will pump sand without damaging it , as they are used all the time as slurry pumps.

Are the prefilters there to protect the pump ? If that is the case I can just use a sea strainer right into the pump and bypass all those consumables and even the priming pump as the D10 can lift and prime itself .

Will the lack of prefilters plug up the membranes? I will be flushing the system after each use, and run the unit every day or two.

Thanks for any ideas .

Regards .
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Old 08-02-2011, 08:39   #2
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Ever look at tap water under a microscope? All kinds of stuff in it. Although I'm sure Tellie will respond when he sees this and give the expert's answer, I'm pretty sure that answer is "most definitely".

You want to get as much of that stuff out of the supply water before it hits the membrane as you can. Otherwise, your very expensive membrane will then be called upon to also do the job of those cheap prefilters and will soon get clogged up, perhaps past the point of the flush's ability to clean them out. The cost of one membrane will pay for more prefilters than you would use for many years of use.

You also really want a charcoal prefilter from your tank to the watermaker for the flush water. You can't always know if the dock water you might have also used has been chlorinated and that chlorine will kill your membrane.

It is that old "ounce of prevention" rule.

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Old 08-02-2011, 08:45   #3
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If he doesn't check in here, typhoon, you might send member Tellie a PM . . . he really is a watermaker expert.

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Old 08-02-2011, 08:55   #4
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I had to ask someone that question. I really wasn't sure if the filters were there to protect the pump or the membranes. I guess I got the answer.

Off to the filter market I go .

Guess I should get a priming pump as well .

Thanks guys

Regards
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Old 08-02-2011, 12:28   #5
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Oh,, One more thing , can I put the discharge below the water line , or should I keep it above .

Thanks again
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Old 08-02-2011, 12:51   #6
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Again, for a definitive answer, ask Tellie, but I believe that you should have it above the water line. The discharge brine water does not have a lot of pressure behind it. My installation manual (a Spectra unit) seems pretty emphatic about it. Also, why have yet another thru hull, below?

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Old 08-02-2011, 15:02   #7
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G'day, mate. Yes, a prefilter is needed to prevent damage to the watermaker membranes. If you use the standard 9 inch filter housing and filters typically found in most big hardware stores you will save money over the long term. As stated above, you will have a less complicated installation if you discharge the brine above the waterline. Cheers.
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Old 08-02-2011, 17:22   #8
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G' day back to you mate

Seems to be the consensus , filters it is .

JT
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Old 08-02-2011, 18:49   #9
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The pre-filters (charcoal and 5 micron) are there for a very important reason. To keep oils and chlorine (fresh water flush) from destroying the membranes. The question I have for you is 40 gallons per hour seems quite high (are you sure)? The product output is directly related to the length of the membranes. I have two 3.5 foot membranes for 200 GPD (gallons per day)

You would need some really long membranes to produce 40 gallons per hour.

Also remember that the higher the pressure, yes the higher the product output, but also the higher the likelihood you could damage a membranes. We run ours at around 800psi never ever exceeding 900psi.

(edit) PS: this gets us TDS of around 300ppm.

Ken
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Old 08-02-2011, 19:11   #10
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Quote:
Originally Posted by missnmountains View Post

You would need some really long membranes to produce 40 gallons per hour.

Ken
At maximum flow rate and pressure, and optimal sea water temperature, 2 standard 40" membranes (2.5 inch diameter) will be good for 40 gph. You'll probably do somewhat less than that in most conditions. I think ROSA will tell you 40 gph for a pair of 40" membranes at 800 psi and 4 gpm flow rate plumbed in series.
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Old 09-02-2011, 08:47   #11
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Quote:
Originally Posted by typhoon View Post
Hi there

Im am building a fully automatic 40 gph watermaker based on a Wanner D10 pump.

As you know this is a great pump to base a watermaker on .


Thanks for any ideas .

Regards .

Yes, the Wanner D10 pumps are great pumps. But would you share with us how you're powering your D10? Also there is a potpourri of D10s including some with cast iron heads. That one is not a good choice.

Designing and building your own watermaker is an exciting challenge that will give you great pride when you finish! Good luck with your project!!!

Foggy
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Old 09-02-2011, 08:49   #12
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Originally Posted by gjorgensen View Post
At maximum flow rate and pressure, and optimal sea water temperature, 2 standard 40" membranes (2.5 inch diameter) will be good for 40 gph. You'll probably do somewhat less than that in most conditions. I think ROSA will tell you 40 gph for a pair of 40" membranes at 800 psi and 4 gpm flow rate plumbed in series.
And you are right on the mark to suggest ROSA!!!

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Old 09-02-2011, 09:47   #13
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Thanks for the interest Foggy.

The pump is a DX10lb. Brass Head . I am driving it with a 13 hp three cylinder Yanmar Marine diesel engine with 100 Hrs on it from a Kohler genrator that went bad . I had to slow the pump down by half because it puts out almost 10 gpm , so i had to use a 10" pulley. I am also driving a ECO tech alternator with the engine directly off the end of the crank . This thing puts out 260 amps at 1800 rpm !! The project is almost done and I will post pictures of the complete project soon. If you go to some of my other threads you can see what I started to do with this engine but changed the pump and alternator for more reliability.

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Old 09-02-2011, 12:24   #14
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GEEZ!!!! POWER YOU DO HAVE!!! I raised the driving question only because that pump requires an electric motor just over 2HP 4 pole or 1725RPM. I considered using the D10 pump earlier in my design but to my knowledge, there are no or at least inexpensive 3HP, 4 pole single phase motors available. 3600RPM is too fast for D10s I am familiar with.

That pump should operate with much less noise than a CAT.

I have most of the piece parts for my setup but right now I am spending all my spare time with a PIC18F controller and still waiting for the development board I ordered. So I am taking time for 'C'.

GO FOR IT TYPHOON!!!! We all look forward to seeing your finished pictures!!! Mine will not be finished before June.

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Old 09-02-2011, 12:38   #15
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Wow, Typhoon --

What that kind of output and a bit of valve/plumbing work, you could have it do double-duty as an emergency fire engine! Not to mention one heckuva bilge pump.

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