Which feed pump for 120 gh watermaker?

[svrevelations]

We need a booster pump for our 150 gallon per hour water maker. The booster pump can be fitted on the waterline and above. We have 12 and 24 volt battery banks as well as 230 volt 50hz generator onboard. Which booster pump would be good?

[slug]

I used a Calpeda centrifugal on the last large water maker

Mid price , bronze . Long service life

https://www.calpeda.com/products/nm-

March also makes suitable pumps.. expensive , high quality

[SVHarmonie]

If you are going to use a centrifugal pump it MUST be below the water line.

Virtually all centrifugal pumps require what an engineer would call "net positive suction head." To convert that to english, centrifugal pumps can not suck water to themselves, it MUST flow by gravity, and not "just barely" but even when the pump is running at full flow there should not be negative pressure at the inlet of the pump.

You do have a problem, for a 150 gallon per hour (really? GALLONS per hour?) watermaker you will need a feed pump that can move on the order of 1500 to 2000 gallons per hour. Finding something other than a centrifugal pump that can do this flow rate efficiently, economically and without constant maintenance is not going to be easy. That's a big pump....

Are you 100% positive you can not get the pump lower down? It's really important.

[a64pilot]

I believe usually that you need as a min three times the water made in raw water flow, as an example my 1.6 GPM pump makes .5 GPM of product water.
I also believe that a centrifugal pump won’t provide enough pressure, cause if it did you would see them used on factory watermakers, cause they are real quiet and will run forever, in other words they would be the perfect pump, but thus aren’t used.

[svrevelations]

Originally Posted by slug

I used a Calpeda centrifugal on the last large water maker

Mid price , bronze . Long service life

https://www.calpeda.com/products/nm-

March also makes suitable pumps.. expensive , high quality

Thank you - but your link does not work.

[svrevelations]

Originally Posted by SVHarmonie

If you are going to use a centrifugal pump it MUST be below the water line.

Virtually all centrifugal pumps require what an engineer would call "net positive suction head." To convert that to english, centrifugal pumps can not suck water to themselves, it MUST flow by gravity, and not "just barely" but even when the pump is running at full flow there should not be negative pressure at the inlet of the pump.

You do have a problem, for a 150 gallon per hour (really? GALLONS per hour?) watermaker you will need a feed pump that can move on the order of 1500 to 2000 gallons per hour. Finding something other than a centrifugal pump that can do this flow rate efficiently, economically and without constant maintenance is not going to be easy. That's a big pump....

Are you 100% positive you can not get the pump lower down? It's really important.

Yes, 150 gallons per hour!

It's for a 50 passenger vessel.

[SVHarmonie]

Originally Posted by a64pilot

I believe usually that you need as a min three times the water made in raw water flow, as an example my 1.6 GPM pump makes .5 GPM of product water.
I also believe that a centrifugal pump won’t provide enough pressure, cause if it did you would see them used on factory watermakers, cause they are real quiet and will run forever, in other words they would be the perfect pump, but thus aren’t used.

Lots wrong here....

No seawater membrane works at ratio of 1:2 permeate to brine flow. If you tried, you would precipitate salts on the surface of the membrane. The BEST membranes for salt work at about 1:10 permeate to brine ratios, and a lot of the smaller membranes are 1:40 or 1:50.

Also, you might go back and re-read. The OP is looking for a BOOST pump, NOT a high pressure pump. Of course a centrifigal pump can't make 900 PSI, and likewise a piston pump can't be a boost pump.

[SVHarmonie]

Originally Posted by Revelations

Yes, 150 gallons per hour!

It's for a 50 passenger vessel.

Resepectfully, you are asking advice in very much the wrong place. Almost nobody here has experience with RO units of that size, and much of the advice you get will not be useful, or even correct. I am not sure how you will sort out the good from the bad. Already most of the posts are not correct, or at least not useful for a unit of the scale you are working with.

I have run units a lot bigger than that, but in industrial operations--not shipboard.

You really need to identify a local vendor who has real experience with units like this, and will stand behind the work they do.

This is not amateur hour. You need to have somebody who knows pumps, watermakers, and boats.

But based on what you have said so far, you will probably want a 220V pump, 12 or 24 will not likely be economical in the pump size you need. You will need to be sure you can feed water to the pump by getting it below the waterline. If you can't do that, then it will be possible, but more specialized. If you can get it down and with a properly flooded suction, the selection process will be simpler, and the end result considerably cheaper, but quite a bit more data would be needed than you have so far supplied.

The best advice I can give you is talk to the people who made your existing watermaker and go with their recommendation. That or pay someone to do the research and calculations that need to be done to be sure of success.

[a64pilot]

Originally Posted by SVHarmonie

Lots wrong here....

No seawater membrane works at ratio of 1:2 permeate to brine flow. If you tried, you would precipitate salts on the surface of the membrane. The BEST membranes for salt work at about 1:10 permeate to brine ratios, and a lot of the smaller membranes are 1:40 or 1:50.

Also, you might go back and re-read. The OP is looking for a BOOST pump, NOT a high pressure pump. Of course a centrifigal pump can't make 900 PSI, and likewise a piston pump can't be a boost pump.

Well look it up, the 30 GPH Cruise RO’s HP pump, pumps 1.6 GPM, and makes .5 GPM of product water.
Then as water is incompressible and you don’t know the output of a boost pump, it’s pretty easy to find, because the boost pump and the HP pump will have the same output.
Watermaker Parts & Accessories by Cruise RO Water & Power

1.6 GPM pump is used for the 30 GPH watermaker, the 2.3 GPM pump is used for the 40 GPH watermaker, so there is two watermakers that use approx 2 to 1 for water output, or product water is 1/3 total pumped water.

So your not even close on your 1 to 10 thought Much less 40 or 50 to 1, not even in the ballpark.
You realize that the brine on a Cruise RO flows out a 1/4” tube don’t you? At 50 to 1 that would be 1,500 GPH out of a 1/4” tube, and the power required to pressurize 1500 gallons of water an hour to 800 PSI would be enormous, way beyond what any Honda generator could make.

Oh and piston pumps are used as boost pumps and have been for a long time.
Look at module 3, that’s a piston pump
http://www.cruiserowaterandpower.com...r_Maker_2.html

Lastly, I’d bet lunch that Tellie is familiar with 150 GPH watermakers and likely larger too.

[slug]

Originally Posted by Revelations

Thank you - but your link does not work.

Hmmm

This is the lift pump... calpeda, well known pump
3/4 inch plumbing
Can’t remember the name of the lift pump sea strainer ...also Italian

Pump is Not expensive ...ac only

This is the water maker HEM 30... similar output to your project

https://extranet.evac.com/dl/008369?revision=1.2

[svrevelations]

Thank you all for your advice!

Originally Posted by slug

Hmmm

This is the lift pump... calpeda, well known pump
3/4 inch plumbing
Can’t remember the name of the lift pump sea strainer ...also Italian

Pump is Not expensive ...ac only

This is the water maker HEM 30... similar output to your project

https://extranet.evac.com/dl/008369?revision=1.2

Thank you for this!!!
The feed pump for the water maker has been removed so we have no clue what was there before - except for the 230 volt power supply wires. However, the water maker looks near identical to the one in your message ... AND, it has a small REM label stuck inside the control panel. We at least now know who the manufacturer is.

[garychurch]

Wow, 120 gph works out to about 3,000 gallons per day. Sounds like you may need a commercial professional to work this issue.

[mvmojo]

The general rule of thumb is that your supply water should be at least 10 times the amount of your product water and preferably 15-16 times as much. Best to target for product water at about 6% of feed water. This keeps the membrane(s) from clogging up with salt. You're looking at a 2000 gph pump or larger! Not gonna happen w/out at least 230v ac. As suggested, discuss with a company who makes RO water plants for shoreside use.

[Lepke]

I use an AC centrifugal pump as a boost pump along with a pressure accumulator. Similar to a shallow well pump. Not much different than my fresh water system. Mounted above the WL. A check valve keeps the water from leaving the pump when it's off.

No big deal to use a centrifugal pump above the waterline, prime the first time. Pump shown is what I use. Because of the tank, it cycles when making water. Rated at 1900gph, up to 49psi. Also a great wash down pump. Cost about $225.

[a64pilot]

Originally Posted by mvmojo

The general rule of thumb is that your supply water should be at least 10 times the amount of your product water and preferably 15-16 times as much. Best to target for product water at about 6% of feed water. This keeps the membrane(s) from clogging up with salt. You're looking at a 2000 gph pump or larger! Not gonna happen w/out at least 230v ac. As suggested, discuss with a company who makes RO water plants for shoreside use.

Where are you guys getting these “rules of thumb”?
According to your rule of thumb my factory 30 GPH water maker should be discharging 300 GPH, or 6 gls a min. But “ideally” 500 or more per hour or 9 to 10 gallons per min.
I can assure you no cruising boats water maker discharges 10 gallons per min, it would like a fire hose if it did, and would take a several HP motor to pressurize and flow 9 or 10 gls per min at 800 PSI. The power consumption would be enormous
Never mind the simple fact that you can pump well over 2000 GPH with even a 12V pump, and or a 110V, you don’t need 230, unless of course your wired 230.