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GRIT · 25-08-2015, 04:13

Hi Tellie,

Yes, I agree with your post. That's why I'm curious about longevity. I know membranes have to be "scoured" by the water flowing through them. And I keep hearing about folks using Higher volume membranes with low flow "home made" watermakers.

Someone even wrote that their Village Marine watermaker was using an SW30-2521 membrane, right from the factory.

My plan was to use a 1gpm wanner pump at one third speed (geared belt) and a Village Marine "dogbone" shaped membrane, which will accept 0.25 gpm flow.

As much as I'd love to have a Spectra unit, I don't see that happening.

Cheers, and thanks, Tellie, for all your great advice on this forum.

Paul.

jcapo · 25-08-2015, 04:38

The pump is working fine. I put a fan on it to keep the pump temperature around 20F rise above ambient. Without the fan the pump temperature would rise to 90F or so above ambient. Wanner says that's OK but I didn't like it.

Until last month were on the hook for the last 20 months on the east coast or the Bahamas making water at least once a week. I accept the fact that the membrane may/will not last as long as it could with higher flow but I can replace it for less than $200.

GRIT · 25-08-2015, 08:13

Jcapo, thanks very much for responding to my query.

Can you confirm that you're still using the 0.55 gph pump, and the sw30-2540 membrane? Are you still making 13 gph of fresh water, and do you happen to have a tds meter?

I agree with you, if you have to replace the membrane every 2-3 years, it's still an affordable way to go about making water.

Is your wanner pump driven directly by the motor, or are you running belts between the two?

It's rare to get reliability/durability reports of home built watermakers, so I'd like to thank you again for responding to this thread.

Cheers.
Paul.

jcapo · 25-08-2015, 09:37

I m using the 0.55gpm pump close coupled to a 1/2HP Leeson 12VDC motor and the SW30-2540 membrane. Along the east coast I always made at least 13gph at 800psi. In some places in the Bahamas on the bank not near ocean water, the output was between 11 and 12gpm with 500ppm TDS due to higher salinity. TDS is mostly 150 to 350ppm depending on salinity and pressure.

I run the watermaker with 12.8 volts and higher at the motor. At 12.8 volts and 800psi the motor current is 31 amps. With my Johnson centrifugal feed pump I consume a bit over 32 amps for 13gph. Not as good as a Spectra but I can't afford one anyway.

GRIT · 25-08-2015, 10:29

Hi Jcapo.

Thanks very much for those numbers. That sounds like a great system to me. You're making tons of water!

I'm going to try the sw30-2540 on my system too. If I'm not happy with the longevity, I can always buy a "little wonder" membrane with the two inch spacer, to fit a 40" housing, later. For now, I'd like to keep the costs down.

Thanks again, and congrats on having made a really nice watermaker!

Paul.

**Tellie** · 25-08-2015, 16:24

Quote:

Originally Posted by svquintana

Hi Tellie,

As much as I'd love to have a Spectra unit, I don't see that happening.

Well then, we just can't be friends anymore

Cheers, and thanks, Tellie, for all your great advice on this forum.

You're welcome. If there's ever anything I can help with just give me a shout, and thanks for the "Thanks"

Paul.

www.HaldenMarineService.com

GRIT · 26-08-2015, 19:22

TickMan · 26-12-2016, 14:39

Quote:

Originally Posted by jcapo

I run the watermaker with 12.8 volts and higher at the motor. At 12.8 volts and 800psi the motor current is 31 amps. With my Johnson centrifugal feed pump I consume a bit over 32 amps for 13gph. Not as good as a Spectra but I can't afford one anyway.

Hello, how did you get enough pressure with this pump ? This pump is produced 2.5 bar which I believe arround 35 psi only.

Guys, where do you buy pressure vessel for this membrane ? I can't find it.

jcapo · 26-12-2016, 14:48

Quote:

Originally Posted by TickMan

Hello, how did you get enough pressure with this pump ? This pump is produced 2.5 bar which I believe arround 35 psi only.

The Wanner Hydracell F/G-20 series is good to 1000psi. I used the F-20-S pump.

Quote:

Originally Posted by TickMan

Guys, where do you buy pressure vessel for this membrane ? I can't find it.

HCTI SEAWATER PRESSURE VESSELS

TickMan · 26-12-2016, 16:55

Thank you very much for so such fast reply, do you use engine driven or electric motor ? I want to build for 12v DC , does this MOTOR will works ?

jcapo · 27-12-2016, 05:22

Quote:

Originally Posted by TickMan

Thank you very much for so such fast reply, do you use engine driven or electric motor ? I want to build for 12v DC , does this MOTOR will works ?

Mine is 12vdc 1/2hp Leeson. That motor might work. Its probably a Chinese import.

TickMan · 27-12-2016, 05:36

Quote:

Originally Posted by jcapo

Mine is 12vdc 1/2hp Leeson. That motor might work. Its probably a Chinese import.

Is it similar to this one
RPM is a little be higher compare to pump, pump is 1700rpm but motor is 1800rpm, is this will be a problem ?

jcapo · 27-12-2016, 11:33

Quote:

Originally Posted by TickMan

Is it similar to this one
RPM is a little be higher compare to pump, pump is 1700rpm but motor is 1800rpm, is this will be a problem ?

That is the motor I used. I bought it on Ebay and it was drop shipped the same day from a Leeson distributor in Tampa, FL.

The RPM of a DC motor without a speed controller depends on the battery voltage. I make a lot of water when batteries are charging at 14+ volts.

Pizzazz · 27-12-2016, 11:43

Dears,

Following recent discussions I updated my watermaker design spreadsheet (attached). A couple of notes for everyone attempting a DIY watermaker. First, it is hard to beat the watermaker package from Cruise RO/Rich Boren. He uses top quality parts, pump, motor and everything comes ready to assemble. Based on my analysis his package is nearly 3x less expensive than the large commercial offerings per gph fresh water produced.

Thus, if you want a 20 gph AC watermaker, you go to Rich. It produces water at the equivalent of DC 5 amps/gallon. Now, if you want something smaller which would mean DC powered then it gets interesting. There are three options:

1. Spectra at around 1.2 amps per gallon, approx. $1000 investment per gph capacity. Very efficient but in my opinion unreasonably expensive.

2. The Katadyn units (best to find a used Powersurvivor 35 or build your own drive for the surplus units on ebay.com). The investment is $300 per gph, makes water at 4 amps/gallon. Great units but you have to leave them on nearly continuously to make useable amounts of water (possible as they make little noise especially insulated).

3. Build your own with a DC motor and pump from ebay. Various combinations work, the best seems to be 1/3 hp motor with 0.5 gph pump driving a 2.5x21" membrane giving you around 6 gallons per hour and you can go up from here. You can expect around 4 amps per gallon if you run your membrane at high flow with 20% recovery or down to 2.5 amps per gallon if you starve the membrane for water and force it to run up to 35% recovery. The cost in terms of investment per gph will be similar to Rich's with substandard components (brass pump instead of stainless, etc.) and the initial investment will be lower but in the long run it is probably not worth it.

The key benefit and the reason for this post is this starvation mode, where you feed the membrane with very little water (e.g. 0.5 gpm flow for a 40" membrane) which allows high recovery and low amps per gallon. 2.5 amps/gallon can be achieved at one quarter of the cost of a Spectra unit. This is at the cost of possible shorter membrane life (non-issue due to negligible cost) and possibly higher salinity (i.e. instead of getting 200 ppm and below you might be getting 500 ppm and below). What do you think about the higher salinity? We put salt in the meals anyway so may be it is not that bad.

Feel free to add your experiences to the worksheet, it would be good to keep a record of our experiences.

S/V Pizzazz