Small watermaker 3 gph

[RaymondR]

Originally Posted by Pizzazz

In designing an RO watermaker, we are bound by available membranes and the need to make 800+ psi pressure. The lowest output watermaker is the Powersurvivor 35 which makes 1.2 gph using around 4.5A per hour. It drives a large piston back and forth slowly. The operation is very quiet but at every cycle (once a second), there is a large thumping sound when max pressure is reached and the valve releases. It can drive you crazy. If the design can be modified to remove this noise, that would be a good silent water maker. It uses 12x1.8” membranes that HCTI makes for around $170 (half the OEM price).

There is also a 06 manual watermaker that makes 0.25 gph, may be it can be modified to take an external pump but the membranes would be hard to find.

All the other pumps use metal valves that produce a fairly significant chatter. You can definitely enclose the pump (it gets cooled down by the sea water anyway but I doubt you would make it as silent as a fridge. I will produce a short video shortly so that you can judge for yourself.

In terms of other technologies (flash evaporation, using engine hot water, etc.), the last time I looked at it, they were at least 3x-5x less efficient than RO. Fun to look at but a pain.

I have a Powersurvivor and it not only makes the thump but the current draw fluctuates wildly as well. I suspect a pressure accumulator between the power recovery and pressure piston would make it work better but have not looked at how one would implement same.

Good info in the membranes, I bought mine with me when I changed boats but have not bothered to hook it up because it needs a new membrane and I could not bring myself to pay Katadynes exorbitant asking price. Thanks.

If you don't like the maintenance costs of RO you would really hate the vapor compression units. The engine waste heat/eductor vacuum units are good and low cost but you need a fair bit of room for the evap vessel.

[Capdave360]

Originally Posted by Pizzazz

In terms of other technologies (flash evaporation, using engine hot water, etc.), the last time I looked at it, they were at least 3x-5x less efficient than RO. Fun to look at but a pain.

About ten years ago I did a very deep dive research project on desalination technologies looking for investable innovations to increase the global potable water supply - with a holy grail of desalination cheap enough for irrigation. With the help of a few experts we parsed every known method into its component parts and unit operations and analyzed the energy and capital requirements, trying to understand where there was even the opportunity to innovate. Along the way we talked to maybe 30-40 research scientists and at least 50 startups. Thermal methods at first were very exciting, but when we really got under the hood the wheels came off. It only works when you have free very high quality heat (i.e. really quite high temp), and the capital costs and maintenance costs are high - the resulting fully loaded cost of water was uninteresting. And there was no headroom for innovation - the existing embodiments were right up against the limits of physics and chemistry and materials science already.

In the end we did invest in one startup, trying to commercialize an innovation out of a US National Lab to build RO membranes using carbon nanotubes based on a patented discovery that the required transport pressure through the nanotubes (which worked to exclude ions) was sharply lower than through the standard engineered polymer films. That discovery/patent was widely mischaracterized in the press as a 75% energy reduction, but that's not possible because the osmotic pressure (what you're overcoming with 'reverse' osmosis) is a fact of nature and can't be changed with technology. But it was still a pretty big improvement in flux for the same energy (or same flux for lower energy), and chlorine tolerant too!

Anyhow we spent over $2M trying to make a POC sample over about 18 months, and failed. There were some team problems, maybe a different team could have done it, but they didn't even get close. No other group stepped up to fund it, and as far as I know no further work was ever done......oh well...

[Capdave360]

Originally Posted by RaymondR

"Not everything is about money. I don't know if you've ever actually operated such a high pressure pump, but believe me, you'll be dying to turn it off after an hour or two. Running it all day - maybe if you're not onboard??"

You're waving a red rag at a rogue bull mate. I used to be an oil driller. The average offshore rig has at least two couple of thousand horsepower, positive displacement, pumps pressure rated to about 6,000 psi, so yes, I have operated a high pressure pump.

Then when one participates in the notorious "fracking" on deep, high pressure wells one uses a dozen or more smaller high pressure pumps to power "intensifiers" (Basically what your Spectra pump is) to boost the pressure up to 15,000 - 20,000 psi. You don't know noisy until you wander past all those GM 871 diesels going flat out.

The cleverness of Pizzazzs watermaker is it's extreme simplicity and use of low cost, off the shelf components. It's the balance of all factors economic and functional which makes it a good design.

The "doer and "haver" dichotomy.

Some of us don't have a lot of money to spend, some of us are just cheap buggers, some of us like to build stuff and some of us just like to dream ie doing. Then some of us just like spending money ie having.

There's a bit in there for everyone.

Interesting background.

For me, I like having my wife come live-aboard cruising with me, so that means having a lot of fresh water without a lot of noise.....no dichotomy.

We meet people all the time who can't do anything on their boats except ask for, and wait for, help - now that's the doer-haver dichotomy!

[Lost Horizons]

Originally Posted by boat_alexandra

What would you recommend if I would rather make only 1 gallon per hour and be as cheap as possible, but 15 amps is fine (plenty of solar)

This: https://www.katadyn.com/en/ch/140-80...yn-survivor-35

Occasionally they come for sale after being decommissioned from ships’ lifeboats for $200, at least that is how much I paid about 12 years ago. These decommissioned units were never used, just a part of a survival kit. Presumably, the membranes need replacement after being pickled for many years. Maybe the o-rings too. Or you can get a new one for $2000 from Defender.
Doubles as an exercise equipment.

[RaymondR]

I tend to the opinion that RO gives the greatest scope for innovation, the high pressure pumping aspect being the most challenging.

Back in the days when I was still pondering on it I decided that the most energy efficient method would be to hang the ballast on a big pivot with a couple of cylinders connected to it and let the pitching of the vessel do the high pressure pumping. If you could set it up to swing transversly you could also implement a roll damper.

[Mr B]

A Karcher pressure washer type pump runs at between 2000 PSI and 6000 PSI,
Ample for a RO watermaker,
There are many varieties of these pressure washers,
Their only drawback is they are 240 Volt,
Running it thru a 3000 Watt invertor solves this problem,
It just need a stainless pressure gauge on the inlet to restrict the pressure to 900 PSI, approx $30-00,
My 240 volt pressure washer cost me $90-00 and works well on my water maker, It runs 2400 PSI,

My 2 Cents worth,

[CrystalSkull]

Thank you Pizzazz, great work!

[seandepagnier]

Originally Posted by Capdave360

ps. Thermal methods at first were very exciting, but when we really got under the hood the wheels came off. It only works when you have free very high quality heat (i.e. really quite high temp), and the capital costs and maintenance costs are high - the resulting fully loaded cost of water was uninteresting. And there was no headroom for innovation - the existing embodiments were right up against the limits of physics and chemistry and materials science already.

We are no where near the limits of physics and chemistry. In theory you can produce 50 liters of water per hour from 1 square meter of sunlight. To do this involves concentrating this square meter to a very small area and super-heating the input water to very high temperatures and pressures which proves difficult. A few small stills have reached 5 liters per hour per sq/m using multiple effects, no where near theoretical efficiency.

With concentrated solar and multiple effect distillation the efficiency is much better than survival type solar stills. On a small scale it's difficult to implement well, but this is also because few have tried and research is mostly limited to industrial scale.

A small solar still of a practical size on a boat can produce several gallons of water a day which is no where near as much as a water maker, but it is still enough water. This combined with rainfall collection and it's unlikely you will run out of water.

The advantage of having a silent operation which is much cheaper and doesn't have the membrane problems seems to outweigh the decrease in water production if you still get enough water.

[CrystalSkull]

Anyone experimented with the longer 21" membrane? I've ordered the pump from Pumptec, haven't decided on membrane size yet. Not really concerned about membrane life and would like the extra gallon or so an hour, really just curious on ppm.

[RaymondR]

Originally Posted by seandepagnier

We are no where near the limits of physics and chemistry. In theory you can produce 50 liters of water per hour from 1 square meter of sunlight. To do this involves concentrating this square meter to a very small area and super-heating the input water to very high temperatures and pressures which proves difficult. A few small stills have reached 5 liters per hour per sq/m using multiple effects, no where near theoretical efficiency.

With concentrated solar and multiple effect distillation the efficiency is much better than survival type solar stills. On a small scale it's difficult to implement well, but this is also because few have tried and research is mostly limited to industrial scale.

A small solar still of a practical size on a boat can produce several gallons of water a day which is no where near as much as a water maker, but it is still enough water. This combined with rainfall collection and it's unlikely you will run out of water.

The advantage of having a silent operation which is much cheaper and doesn't have the membrane problems seems to outweigh the decrease in water production if you still get enough water.

Yep, a technology which has been under utilized. I pondered making one of about 12 square metres fixed on either side of the boom to double as a deck shade.

[Franziska]

Hi Jim,

would you be able to share details & a precise part list on your 12gph DIY design?

We would love to follow your design, but, ideally with two modifications, it needs to run directly of the 220v output of our 2kw FME genset and we would be willing to use a stainless pump.

I like the smaller design in the title of this thread, but we are not happy running the genset when not on board.
So, a watermaker with a higher output and less running time seems better to us.

Still if you say the 2kw genset can produce 10gpm or less at most, we'll be absolutely okay with that.

We are very much on a budget though and as such, an Spectra is way out of the possibilities.

Maybe you can be so kind and share details?
That would be really generous.

Thanks, Fran

Originally Posted by jimbojonesbos

Just an update for anyone considering building this. I am putting together both a 12gph 12v watermaker that should pull about 90 amps @12v, and the 3gph system in this thread. I have been unable to find the pumptec 116c with the .105 cam as anything other than a special order and consequently I'm getting quotes in the $650-$675 range.



The key elements of the 3gph design, as of Feb 2020, have the following prices:


-116c-105 pumptec HP pump , $675 from pumptec direct or through a dealer

-14" membrane housing $320 from freshwatersystems.com
-membrane, $221 from freshwater systems
-stainless needle valve, ~$100 from mcmaster carr
-flow meter, also about $100 from mcmaster carr
-prefilter housing, ~$20 from any plumbing supplier
-prefilters, ~$5 a piece from any plumbing supplier
-NC 1000psi switch , ?? I have been unable to source one.

-assorted plumbing fixtures not included



I'm looking at about $1,500 for the 3gph design. Still comparatively low cost and will be great to be able to run it off of solar alone, but I have not been able to get to Pizzaz's sub $1k figure at current costs. costs are comparable to the 12gph one I am building using a cheap(treated as a consumable) brass HP pump driving a 40" membrane partly due to the fact that most components are the same and the 14" membranes and housings are more expensive than the 21" and 40" ones by a fair margin.


As an aside I am building both as a technology demonstration / testbed for use in disaster relief situations, not strictly for use on a boat.

[rak]

Pizzazz, sent you a PM about buying a pump, are you still able to source them? I have all the parts to build the system except the Pumptek pump, using a 2.5-21 membrane.

[wingssail]

Originally Posted by seandepagnier

Would it be possible to put it in a sound proof box? I have seen it done with engines.

What would you recommend if I would rather make only 1 gallon per hour and be as cheap as possible, but 15 amps is fine (plenty of solar)

I did just get an evacuuated tube for about $100. It is great for cooking as I have used it every day for more than a week even with clouds it cooks (takes much longer) it can also evaporate more than a gallon of water a day which puts it on similar price point as homemade watermakers.

As someone else mentioned you can find used Power Survivor 35 water makers quite cheaply. Some are unused. The rebuild kit is not expensive and easy to install, the membranes can be less than $200 if one is needed.

We've been using one (part time) for 25 years, it is going strong. It produces 1.3 gal per hour. It is on its third membrane and 2nd pump rebuild.

[OneTwoSail]

Commenting to follow here. I think this is a great design. Curious how the double pump version is going if you have any feedback.


One of the benefits of DIY that hasn't been mentioned so far, is that if you've built it, you can fix it!

[PirateGuy]

PM sent to Pizzazz for buying a pump. I’ve modified my old PowerSurvivor80E to take a standard 2514 DOW membrane (new pressure vessel) and would like a backup pump as well. I realize I need to add a downstream needle valve to maintain pressure within the pressure vessel, as the original PS80E pump is energy regenerating from the pressure vessel brine discharge line.