Poor Man's Watermaker ?

[northerncat]

i understand how watermakers work and the principles behind it, what i want is something that will put out 20-40l(4-8g) per hour, now all the ones i have been able to find and the ones on this forum talk in the 20-40gph range, on my cat i plan on carrying 200l with the capacity for 300l, i want something that i can for 1-2 hours that will replace my daily used amount which i hope will be in the 40l per day range, now i am going to have one of those 2kw gas generators but again this really is for running purposes 1.6kw which isnt enough power to run the 3hp ac motors most people are talking about

[northerncat]

i guess i would like to find someone who has made a dc watermaker that produces the water i want and purchase the same motor and pump here in aus
sean

[northerncat]

what kind of watermaker did you make bob? ac or dc?
sean

[bob46777]

It's neither. I drive the high pressure pump with a single cylinder diesel engine which also driver a 110 amp alternator. I make 48 GPH of water and charce my batteries on 2/10 of a gallon of diesel.

[northerncat]

sadly for me i dont have the luxury to afford the weight of a diesel motor and am installing outboards fo your solution wont work for me
sean
sadly still chasing a dc desal

[Chrisc]

I need water, and I need battery charging. Honda put out a nifty little petrol generater that is ultra small and ultra quiet. Output is 12v8amp, and 240v/1000watt. The 12v side battery charges through an automotive type alternator so wont push up deep cycle batteries past the 70% stage, but presumably one could use a multi stage charger on the 240v side? They are a lot cheaper than the 3 stage regulators fitted to engine driven alternators.
Would 240v1000watts be sufficient to run a watermaker pump when not battery charging? These generator units use 0.6 (?) litres gasoline/hour and where I live (NZ) they cost NZD1900.

Chris

[GordMay]

1,000 Watts (1kW) is about 4.2 Amps at 240 Volt (8.3 A @ 120V), which is sufficient to run a fairly small Watermaker.
For instance, a 7 gallon/hour watermaker (1/3 HP Pump Motor) may require only 3 FLA (Full Load Amps@ 240V) to run (FLA); but over 5 LRA (Locked Rotor Amps @ 240V) to start at 60Hz. Lower (50Hz) frequencies will require a little more power.

[northerncat]

this is a question i have been pondering as well as i understand it 1hp=750w so a 1kw generator should run this however you have to factor in startup current which can be up to 3* motors running draw, the other hassle with this solutuion is that it consumes petrol, which you then have to carry as well as diesel and you have a hassle if your genny dies, i think it would be simpler to have a dc powered one and use your generator to keep your battery charge up while its running
sean

[GordMay]

Although 1 Horsepower is nominally equal to 747 Watts ~ Motor Efficiency* & Power Factor, and Mechanical Efficiencies* will increase the power (watts) demand to as much as 1,000 Watts per H.P. As Sean indicates, starting currents (LRA) can be as much as 5 times running currents (FLA).

The best information is taken from the actual Motor Nameplate or manufacturer's specifications:
Full Load Amps (FLA) = Running Current
Locked Rotor Amps (LRA) = Starting Current

*Actually In-efficieciencies

[northerncat]

maybe a dumb question on watermakers but does the fresh water that comes out have enough pressure to make it back to the fresh water tank? i ask because i am making my own in about a month(researching at the moment) and where i will put the watermaker is 4ft lower and about 15ft from where the water tanks are and i am curious as to whether i would need to put a booster pump into this, i would assume that the fresh water would have lost some of its 800psi but hopefully? not all of it, what sort of prssure does it come out of the membrane at?
sean

[Brent Swain]

My book Origami Metal Boatbuilding ' tells you how to build a 540 gallon a day engine driven warermaker using a pressure washer pump for under $1,000 CDN
Brennt Swain
brentswain38@yahoo.ca

[Alan Wheeler]

How does the pressure washer pump handle Salt water????

[northerncat]

thanks to mister swain who keeps trying to plug his book sadly however as he keeps saying this is for engine driven systems now as a catamaran sailor i do not want to run my engines just to power a watermaker/generator and so want a 12v unit, i like alans question but maybe it should be rephrased as what ias the life span of a pressure washer pump given that it will be pumping salt water and only getting rinsed in fresh
sean

[ssullivan]

This is the BEST solution I've ever seen for a liveaboard who doesn't visit docks.

We decided against the watermaker, figuring 140gals of water was enough. As it turns out... it is... almost. We can make it a month on that amount of water (dirty, filthy sailing scum!). ha ha ha

But seriously, water is our limiting factor. We are looking to build a watermaker this winter, but unfortunately already have a great generator. If I were starting from scratch, I would do exactly what Bob did below. It's the most reliable and efficient way to go.

Sure, solar and wind are great, but you'll always need that backup generator and diesel for the inboard. So... why not use the "backup" generator to do everything you need?

Since we have a diesel genset already, my watermaker will be 120VAC powered, off that main power plant.

For the original poster: You are left with a lower GPH watermaker if you run the DC models off of whatever DC charging you anticipate. This just means a longer petrol genest run, or expensive solar/wind. This is another advantage of just biting the bullet and getting an AC genset. It will run many types of inexpensive non-marine appliances. If you get a really powerful one, you only need to run it 1 hr per day to use computers, refrigeration, house loads AND watermakers. It's extremely efficient.

Originally Posted by bob46777

It's neither. I drive the high pressure pump with a single cylinder diesel engine which also driver a 110 amp alternator. I make 48 GPH of water and charce my batteries on 2/10 of a gallon of diesel.

[jim lee]

Have any of you actually tried to live on watermaker water? Our boat only carries 20 gal of water, so I installed a PowerSurvivor 35 unit. Yes it was able to fill the tank, yes with only solar (16Amps of panels) we were able to make all the water we needed. Well, unless we wanted refigeration, one or the other choose..

But living on 100% watermaker water (Doing passages) After a while it was like drinking thick air, didn't do much for quenching your thirst.

As a water tank "extender" it worked great. But as the sole source of water it wasn't so hot. The mineral depletion thing needs to be delt with.

-jim lee