12 volt watermakers, which one?

[Pizzazz]

Originally Posted by mitiempo

Spectra watermakers operate at 800 psi.



The Spectra 150 produces 6 gallons /hour @9 amps. To do this the low current feed pump has a pumps 1.7 gallons/minute - 102 gallons per hour. The product water is 6% of the feed water through the membrane.



Using your number of .21 gallons/minute (12.6 gallons/hour) and assuming the same percentage of product water to total flow you will get 6% of that 12.6 gallons or 97 ounces of product water per hour.



Flow rate has to match the membrane as well - too low a flow rate is a problem.

All DC watermakers without pressure intensification operate at 20-30% recovery. You can either optimize for membrane life (high flow, 8% recovery, 5-10 year lifetime for membrane) or for low power (low flow, 30% recovery, membrane life of 2-3 years). You can chose what you are optimizing the system for, to me it is obvious that you need to optimize for low power and buy membranes as needed.

Spectra can do both, low power and high flow due to the pressure intensification device with energy recovery. It is neat but noisy, patented and expensive. It does give you 1 AHr/gallon though.

Regular DC watermakers operate at around one gallon per 3 AHrs, some as high as 4 AHrs. The larger the watermaker, the more efficient it is, mostly because the DC electric motors become more efficient with size.

The design goal here is to produce an off the shelf watermaker that makes 3-4 gallons per hour, using a proper pump (forget these pressure water pumps), very low noise, at around 3 AHrs per gallon. The idea is to leave it running for a few hours a day without being bothered by the noise. I think I am nearly there with this pump/motor combo, should know within a couple of weeks. Also, I want the cost to be below $1,000 retail because I believe this opens a totally new market of casual users vs. the regular cruisers who need to go with Spectra, that I agree with.

[ThereAndBack]

Interesting work Pizzazz. Thanks for sharing with the community.

I'd be interested in what parts you end up using and where you purchased them from. I've often thought of building my own as well.

[john61ct]

Originally Posted by Tellie

If you want cheap 30-40gph then you have to go AC to make any sense.

Cheap was not mentioned, and often different from value long term.

Rich has said no worries, so likely has a motor already in mind.

Just putting it out there, alternatives are always good.

And yes, ICE running to make water is a given for me, freezing holding plates and refilling LFP as well, maybe making waffles too 8-)

[mikedefieslife]

I've been looking at some of the European 12v watermakers with energy recovery systems. (Osmosea, Eco-sistems, Schenker etc..)

The the smaller 20-30l units seem to run 2.5x21" membranes from European manufacturers such as Oltremare. Presumably though a Ropur (FR80-2521) or a Dow (SW30-2521) would be suitable replacements?

Secondly, when asking about spares/maintenance kits a 'pump head' like the Fluid-o-tec PO 70-400 was mentioned as something to carry and replace annually/biennial (depending on usage). I'd never heard of this before. Surely these pumps aren't so fragile?

Any thoughts on this?

[GaryAlan]

I think 12V watermakers use too much power/need to run too long. If you have the Gen, better off with a 120V model, or have a ton of solar!

Here is an interesting read on the topic: https://sailingsatori.life/rainman-watermaker-review/

[GaryAlan]

I had an old Little Wonder, too much power for too little water. This blog talks about the same thing and the switch to a 120V system. https://sailingsatori.life/rainman-watermaker-review/

The spectra drawing only 9 amps sounds nice though!

[newhaul]

Originally Posted by GaryAlan

I had an old Little Wonder, too much power for too little water. This blog talks about the same thing and the switch to a 120V system. https://sailingsatori.life/rainman-watermaker-review/

The spectra drawing only 9 amps sounds nice though!

spectra Ventura 200. 14 watts per gallon 10 amps draw
The Ventura 150 17 watts per gallon at 9 amps draw
Go for the 200 at 8.3 gallons per hour.

[CarinaPDX]

Originally Posted by GaryAlan

I think 12V watermakers use too much power/need to run too long./

Just like everything else electrical on a boat being efficient is important but so is usage. If one is careful about water consumption then a 12V system works well, but if you really must have a long shower every day for everyone, wash down the boat to remove salt, etc, then it is necessary to scale up. The actual efficiency is only one aspect. Scaling down consumption is just as effective - you just have to accept you are not living in a suburban home anymore...


Greg

[john61ct]

Again, the real tradeoff is between high GPH vs low Watts per gallon.

Yes the OTS DC-powered units are designed for the latter.

But that is not inherent to the technology, it is not difficult to make a high volume / less energy efficient unit that runs off DC.

It just requires DIY or a custom order, not offered OTS, because most boaters with high demands already have AC generation aboard.

[fgd3]

I went with a PowerSurvivor 35 because I can produce the 4 amps it requires. Even though I might be able to produce more water per watt with a bigger unit I just can't produce that many amps.



Fabbian

[newhaul]

Originally Posted by fgd3

I went with a PowerSurvivor 35 because I can produce the 4 amps it requires. Even though I might be able to produce more water per watt with a bigger unit I just can't produce that many amps.



Fabbian

I have the same unit but its not about instant amps its about ah per run and recoupment
( how long it takes for the batteries to recover the power used for say 10 gallons of water made.)
doesn't hurt my initial outlay for the used unit was 500 bucks including the prefilter .