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Old 30-09-2011, 07:07   #1
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Lift Pump for Watermaker

Guys,

I'm installing my watermaker and was hoping to get a couple thoughts on something I'm thinking of doing.

I'm looking to feed my CAT347 HP pump with raw water from a tee after my strainer to the engine (generator next year, engine this year). I'm looking to do this using my washdown pump (4gpm, diaphragm with 1.5' lift).

Any reason not to either Tee off of engine inlet (1" plumbing) or use diaphragm pump for lift??

Cheers,

T
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Old 30-09-2011, 13:53   #2
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Re: Lift Pump for Watermaker

The diaphragm pump is a positive displacement pump which will be feeding another positive displacement pump, not a good combination. If the feed pump is mounted below the water line then a centrifugal pump is what you want. Smaller, cheaper and more reliable. Make sure all hoses are sized as large as possible.
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Old 01-10-2011, 10:44   #3
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Re: Lift Pump for Watermaker

I agree, diaphragm pumps are troublesome in watermaker applications. Also before you go too cheap make sure both the pump and motor are rated for continous run. Many of the inexpensive pumps found at the Marine Candleries are not and rated intermittent (short time) By useing short time rated motors the manufacturer is able to reduce size, weight, and cost. Thus the cheaper priced motors often found. Look for the "CONT" on the motors face plate.
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Old 01-10-2011, 11:23   #4
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Re: Lift Pump for Watermaker

Hmmm.... dont remember using a feed pump for my Cat watermaker pump.... It was about a foot above waterline...
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Old 03-10-2011, 06:15   #5
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Re: Lift Pump for Watermaker

Thanks for the feedback. Sounds like the diaphragm pump is not the best choice. Especially since the CAT pump will need 4 GPM and the diaphragm will kick out 4 GPM. Too close for comfort. I've got a Paragon Jr pump (rated for continuous use) that is a rotary pump set for 7 GPM.

I'll most likely give that a shot unless there is a huge reason not to???
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Old 03-10-2011, 06:44   #6
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Re: Lift Pump for Watermaker

Quote:
Originally Posted by ohanasailing View Post
Thanks for the feedback. Sounds like the diaphragm pump is not the best choice. Especially since the CAT pump will need 4 GPM and the diaphragm will kick out 4 GPM. Too close for comfort. I've got a Paragon Jr pump (rated for continuous use) that is a rotary pump set for 7 GPM.

I'll most likely give that a shot unless there is a huge reason not to???
Can't see a reason not to. 7gpm for a rotary pump is a bit different than 7gpm for a CAT pump. 7gpm for the lift pump means that's how much it will deliver total. The Cat pump rated for 7gpm is how much it delivers at the full operating pressure it's rated for. Depending on how much your watermaker requires to operate properly the difference should pass through the brine discharge. This is an area where the proponents of building watermakers is easy start to find out otherwise. The pressure is easy to figure, getting pressure and flow is a bit trickier, finding the proper balance between the two to fit the unit made where it will run efficiently, and last without self destructing from either too much or too little is the trick.
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