DIY Watermaker: Pros & Cons

[svcattales]

I'm 95% done with installation of my home-made watermaker. It runs off 12V power and should produce 6.5 gal/hr. Today I tested all my connections for leaks, ran the boost pump, turned on the pressure pump and pressurized the system to 800 psi. The only leak was a missing o-ring in one of the filter housings... found it on the floor. The next step is to install the membrane in the pressure vessel, but since membranes have a shelf life, I'm waiting till fall to purchase it.

If you are considering making your own, here are some of my observations:

Pros:

The cost is much less. I will have slightly over $1,900 invested after buying the membrane.

I used readily available components that are not sole source items and are reasonably priced; e.g., membrane $164, pressure vessel $215, 3 filter housings with filters and mounting bracket $49, etc.

I'm now an expert on my own watermaker since I know what makes it tick.

I did a custom installation of all the components and the Admiral is happy that I didn't fill up one of her storage lockers. For example, I mounted the charcoal filter housing under the head sink where it took up very little useable storage.

Cons:

The plans I bought were simple and all the major components were easy to find, but fitting them all together and making tons of different plumbing connections was a challenge. This was a time consuming job, so it's not something to tackle on one weekend. If you don't have lots of time, write a check and git-R-done.

The electric motor and pressure pump are mated together and are very robust industrial components, but they are not energy efficient. The 1/3 HP electric motor looks like the starter motor of a Peterbuilt. The more efficient commercial water makers with the same output may only draw 8 amps DC while mine will draw about 28 amps. I bought two extra solar panels for $400 using some of my DIY savings, but I will burn lots of amps making water. When I make water underway, that will not be a big deal for me. If the sun is out and the wind is blowing, I can run the system off my solar panels and wind gen. Would it be nice to burn only 8 amps? Sure enough!

My watermaker isn't a flip the switch and forget it deal. I have to manually turn valves and flip switches. After making water, I have to turn another valve to do a fresh water flush. It's not that complicated, but it is a hands-on operation. I made a checklist so the Admiral and other non-builders can still make it work.

Here are some pics:

[JulieD]

Where did you buy the plans?

[svcattales]

Originally Posted by JulieD

Where did you buy the plans?

I bought the plans on Ebay from a sailor named Bob Englar. His email address is benglar (AT) tampabay (dot) rr (dot) com

[svcattales]

Originally Posted by JulieD

Go ahead and take the email address off the post. I've got it noted and will write to him. Thanks for the info! This might be just exactly what we are looking for.

If you decide to build this watermaker, I made a modification you might like. Bob's plans involve using a 2 gal bucket to catch product water for fresh-water flushing the system after making water. It looked like too much work so I tapped into my pressure water system for flushing and added a charcoal filter to remove chlorine. If you need more details, let me know.

[Pblais]

Address fixed

[anjou]

What prevents you/anyone finding a motor which will draw less power? Where is the 20 amp difference in efficiency?

[JulieD]

Greg,
Did you find it easy to get all the parts that you needed?
~Julie

[svcattales]

Originally Posted by anjou

What prevents you/anyone finding a motor which will draw less power? Where is the 20 amp difference in efficiency?

Anjou, Good question. After some serious head scratching, here is the answer from an electrically-challenged cruiser:

There are more efficient motors out there, but the motor is sized based on the power needed by the pressure pump. The motor was also a "bolt together" mating with the pump which simplified construction. My pressure pump is an industrial "brute force" pump designed for commercial use rather than for efficiency. It looks like it could suck in a tomato and spit out spaghetti sauce. The high tech pumps like Spectra have a patented system which intensifies the pumping action at much greater efficiency. I know "Strygaldwir" was able to find a used pump and made his own very efficient system. I've heard that these types pump/motor combinations are hard to find and you may be tied to the manufacturer for spare parts.

Like lots of boat gear decisions, there are lots of tradeoffs. I decided to bite the bullet on power consumption in return for simplicity, low initial cost, and readily available spare parts. I can generate 24 amps from solar panels so I can still run the watermaker without starting engines when the batteries are up. If the wind is blowing I can generate enough amps from wind gen to break even on consumption.

[svcattales]

Originally Posted by JulieD

Greg,
Did you find it easy to get all the parts that you needed?
~Julie

Julie, The plans included a parts list for all the major components with web addresses and prices. All the web sites checked out and had the parts in stock. In several cases the prices were a little higher than in the plans due to inflation, but I had no problems finding all the parts. I found most of the plumbing connectors in Home Depot and hardware stores. The high pressure hose from the pressure pump to the pressure vessel is a custom item made at machine shops or auto parts stores that can make hydraulic lines.

The pressure pump came with a detailed manual and a parts list. They also sell repair kits for wear items like valves and diaphragm (I haven't priced it yet).

[svcattales]

We just returned from a 4 mo trip to Bahamas and used our new watermaker for all our needs. Overall, we were very happy with it and the low intitial cost was worth the tradeoff in efficieny and cost of production models.

The amperage draw was higher than expected, but water production was also higher. When system was pressurized to 800 PSI, amp draw was about 35 amps rather than 27. The designer told me to expect 6.5 gal/hr, but we usually made a lot more. On average we made about 9 gal/hr and very often 10-11 gal/hr. (Production has lots of variables like salinity, temp and battery bank voltage). I was hoping to run the watermaker off my solar & wind power, but load was too heavy so I only ran it when we were motoring. Since we normally moved once/wk, we made most of our water underway and that wasn't a problem. On a long motoring day, we made as much as 70 gals which would normally last us two weeks.

If I had to do it all over again... I would.

[capt_douglas]

Interesting thread. How do you know when your product water is pure enough to go into the tank (time, volume, tester, etc)?

If you're an SSCA member, I think a member did a writeup on his homemade watermaker. That might give you a few more ideas (or confidence). Watermakers aren't complicated, just high pressure and high current draw, but it seems to me that being able to linger in a great anchorage or avoid the high price of less than stellar water ashore is a real incentive.

[Ziggy]

The current (May/June 2010) issue of Good Old Boat - Welcome to Good Old Boat Magazine has an article on building a watermaker (Part 1, Part 2 promised for the next issue). This design uses a direct power takeoff from the engine to drive the pump and produces up to 22 gal/hour of fresh water.

[scotte]

Originally Posted by capt_douglas

Interesting thread. How do you know when your product water is pure enough to go into the tank (time, volume, tester, etc)?

We use a combination of TDS tester + taste.

[ghaffy]

Hello,

I am new to this forum, and this is my first post here.

I am Andreas from Vienna, Austria (Europe). Our boat is a Albin 25 Motorsailer (rig down most of the time), and I built our watermaker during the last winter. Now - as summer has almost ended here - we have collected our first extended experiences with it, and we (my wife Hilde, our 3 kids 2-8 ys old, and I) are quite enthusiastic about it.

Everything that was said in this thread may only be emphasized by us.
I did not buy a plan or so but collected all the necessary ideas, concepts, and knowledge by means of google.

Our installation is different in one major point: Instead of buying a bloody expensive CAT pump or so I used an ordinary small high pressure washer for 59,95 USD. Of course it is not made from SS or so, and the question was how long would it last. In summer we do cruises of about 8 weeks on the Mediterranian. And in case it would not last I had a second one aboard as a spare part.

The power concept is: The high pressure washer uses normal household voltage AC (230 V AC here in Europe). So it runs off our 2500 Watt AC/DC inverter. In order to limit the Amps draw and for softstart-reasons I also added an electronic control device (about 30$) to regulate the washer from zero to maximum power. (We count in Watt here. The washer needs max. 1400 Watt at 230 V; at 12 V via the converter it draws roughly 100 Amps at the pressure of 800 p.s.i. I regulate it down to about 50 Amps).

At this setting the fresh water rate is 10 to 15 gph.
During 6 weeks we produced 800 US gallons of freshwater without any problems. As we are motoring we don't have serious power problems.

Below there are some pics from our installation (the control panel has been made "nicer", this was rather the test installation).

Anyway, we want to change the high pressure washer to a engine driven pump (requiring 50-100 Amps per hour for 1 or 2 hours continuously is going to kill the alternator, definitely it has killed 2 belts in 6 weeks). Due to space restrictions in the engine compartment I am looking for a slim pump.

Now, when I saw the pump on the pics there, I was totally attracted.
Could you please tell me what brand/type of pump this is.

Thank you so much.
Andreas
MS "Dido" (Albin 25 AK)

(Should you be interested in our watermaker-story you are welcomed on our private website Welcome to the ALBIN 25 Site with even more details.)

Pressure vessel


"control panel"


DC/AC-inverter


This is the pressure washer that we used:


The washer pump installed in the bilge:


The Filters:

[Tellie]

Hi Andreas,

I just commented on your introduction post. My daughter is in Vienna and the wife and I are going over in November, we have to meet up for a beer. It's especially interesting that you posted your DIY water maker. I'm in the water maker business and have been involved with many home built water makers. I noticed in your website that you cruise in France and along the Danube. I have one question for you. Isn't where you are cruising in fresh water? Have you used your boats water maker in salt water yet? There will be a difference. Check your Private Mail box.
Best Regards Tellie