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Old 20-05-2009, 03:45   #1
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Idiot's Guide to Watermakers, Please

Hi.

Whilst im no stranger to engineering and plumbing (im a heating engineer), the concept of reverse osmosis is all new to me so could you please give me an idiots guide to the whole process of onboard watermaking.

ive done some reading and have a few thoughts.

If the daily average useage is say 50 galls, and all you need to do it top up the water tanks, then isnt it better to produce 2-3 galls per hour, every hour as this uses less electricity (assuming its 12v) and the membrane is in constant use which is better for it?

Please talk me through the process, the membrane and its peculiarities, how is it backwashed to stay clean, etc etc

Thanks
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Old 20-05-2009, 06:30   #2
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Originally Posted by anjou View Post
1. If the daily average useage is say 50 galls, and all you need to do it top up the water tanks,
2.then isnt it better to produce 2-3 galls per hour, every hour as this uses less electricity (assuming its 12v) and the membrane is in constant use which is better for it?
1. Fifty gallons/day fresh water consumption suggests either a large crew, or very luxurious* (wasteful?) Lifestyle.
One common recommendation for passagemaking is to assume a consumption of about 2.5 to 3.0 gallons per person per day.

* Long, Hot, Freshwater showers consume huge amounts of energy (heating & desalinating).

Maggie could enjoy a 5 gallon shower, including wash/rinse of her long & thick hair.
I used < 1 gallon to rinse only, after saltwater bathing.


2. Watermakers do like to run often. Running the watermaker daily for a couple of hours, coupled with automatic back flush, keeps the membrane clean and in good working order. There is little advantage in running the watermaker for longer daily periods*.
A membrane not cleaned in a week can get bacterial fouling. If you do not use the watermaker at least weekly, you should flush the system or put it into storage mode (pickling). Membranes should not be stored dry**.

* Except when running off battery power alone, a longer run time at lower loads, will extend battery life.

** The membranes should be permanently immersed in liquid: either sea water before treatment, fresh water provisionally stored, or sterilizing liquid if the water maker is not used for extended periods of time.


Selecting the optimum system requires consideration of your boat's power capability, and the number of hours per day the system will have to be operated to provide the desired quantity of water. You may want to run it while the generator is on, or while the engine is on (during battery charging, air-conditioning, moving the boat), rather than off battery power alone.

Higher capacity watermakers are generally more efficient, having lower energy requirements per unit volume of fresh water produced.

Perhaps a run time of 2-5 hours per day is reasonable.

A 2-3 GPH watermaker would produce 4 to 15 gallons per day, when run for 2 to 5 hours. This should be minimally adequate for a cruising couple; but I would prefer the ability to go about 2-3 days without topping up.
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Old 20-05-2009, 09:02   #3
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Watermakers are the device on a boat most likely to break (according to a Blue Water Sailing survey). That said, you want to have a unit that will replace the water you have used as quickly as possible. 12 or 120 v. depends on your boat. When cruising, I run the genset or engine about 2 hrs/day to charge batteries and cool down fridge/freezer. My water maker makes 36g/hr so the water is of no cost. Remember that you can buy alot of water anywhere for what a water maker costs.
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Old 20-05-2009, 09:55   #4
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When cruising, I liked to run my water maker ever other day. This, I believe, maximizes the production and minimizes operating and maintenance costs.

As Gord pointed out if you leave the membrane unused for extended periods of time, you run the significant risk of growing bacteria that degrades the membrane. If you run often, the bacteria never gets an opportunity to multiply to any significant degree.

Assuming a 12 Volt system means you are running electrical motor(s). These motors and their pumping mechanisms will wear out (some a lot quicker than others). Running continuously will wear them out over a short elapsed time. Consider a 5000 hour MTBF, you'd expect the motor to to last less than a year. Motor replacements can run from $200 - $1000 for the motor only, and the pumping mechanism (diaphragms, rotors, impellers, etc) are not inexpensive either. So, minimizing run time will help minimize the cost.

Power management is a significant issue on a cruising boat. Ideally one needs to balance the power one uses with the power one produces. As Speciald was implying running the water maker when one has excess power has significant power management benefits. If you are running your generator/genset it normally has the ability to produce more energy than you can put into you battery at any given instant. You can use that excess capacity to run your water maker, heat water, run microwave, make bread....etc. But, you're not typically going to run that generator/genset for extended periods of time. You'll probably want to minimize it. (Your neighbors will appreciate you MUCH more!) Most folks try to create systems where they only run for an hour or two every day. Therefore you want to try to have a system that can replace the water you use in the time frame allotted for charging.

Once again, as Gord pointed out, 50 gallons a day is a LOT of water. We were not that water frugal and my wife and I used about 8 gallons a day. This included showers and we did not use salt water for dish washing. (we did shower together, but that's another thread! ;-)

We loved our water maker while cruising. We saw a lot of time, effort and attention paid to replenishing water supplies. You had to hit a dock that offered water, or use cans to haul water back from a water supply. Definitely doable, but, we were very happy we didn't have that concern. But, the price of watermakers is close to outrageous! We were able to put one together based on a Spectra 380C Design. We used fairly available, off the shelf parts (except for the Hydraulic intensifier - Clark pump). This system cost us around $1200 to put together. We didn't really have any desire to spend the $5,000 it seems most vendors wanted for a system.
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Old 20-05-2009, 12:49   #5
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Great and thanks guys, this is what i wanted to hear, common sense and good advice.

Im a girl who loves to feel fresh and clean but maybe living amongst people who are the same provides that peer pressure. Maybe living amongst the sailing community where the emphasis in life is different, being a glamour puss isnt a priority. Therefore, im sure i can revise my water useage.

I understand the logic of running the system occasionally but maximising the use. It adds up to less wear and tear. MTBF?, .....Max Time Before F***ed? ok, that makes sense too, the clock is ticking for us all.

Whilst i understand the unit cost of production in terms of investment and running costs, having fresh clean water is the fundamental need in all our lives and who knows where the future lies and I dont know if I would be able to carry water cans or have access to the dock.

$1200 is about £900 at todays rate and I dont think thats an unreasonable price for my own independant water supply. The annual water bill for my appartment is @ $400, and i have the convenience of opening a fawcet.

I see the logic of having days when you start the gen and do all the chores in one go like the washing, baking, water making etc. Max efficiency.
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Old 20-05-2009, 20:19   #6
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I like max time before Fxlk!!! Much better than Mean Time between or before failure.
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Old 21-05-2009, 05:38   #7
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One needn’t be a “water-hog”, to maintain good grooming. For instance Maggie tries to never appear in public, even when cruising, without subtle make-up, and clean hair (a “glamour puss” ?).

A luxurious ten-minute shower takes about 50 U.S. gallons (190 L) of water, while a naval shower* can take as little as 2-3 U.S. gallons (7-11 L).

The 2-minute Naval Shower:
1. Turn on water, & wet body
2. Turn off the water
3. Soap up and scrub
4. Turn water back on, & rinse
5. Turn water off
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Old 21-05-2009, 06:21   #8
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I used to live in a 23' trailer on a farm with no electric or running water and I would wash in the river, even in winter, but that was 26 years ago.

AS luck would have it, a friend on an energy renewables forum, came across a RO system in a dumpster out back of a launderette and once i mentioned im looking, he messaged to let me know he has the unit but its unsuitable for his earthship housing needs.

I need to check it out but he described it as:-

3 x 20" containers, which have 1 particulate filter (spun/woven type) and two carbon filters (one is plain carbon the other I think is a carbon plus chlorine etc filter)

3 x 10" containers, each of which has an RO membrane which seems to be made up of rolled rubber-type membrane.

1 x 24v boost pump, + 1 pressure sensor.

The way I understand it, the routing was in the following order:

Water supply
particulate filter
pump
carbon pre-filter
3 x RO membranes
carbon post filter (though some systems have this ahead of the RO membranes)

Maybe this will do the job?
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Old 21-05-2009, 06:32   #9
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Quote:
Originally Posted by GordMay View Post
One needn’t be a “water-hog”, to maintain good grooming. For instance Maggie tries to never appear in public, even when cruising, without subtle make-up, and clean hair (a “glamour puss” ?).

A luxurious ten-minute shower takes about 50 U.S. gallons (190 L) of water, while a naval shower* can take as little as 2-3 U.S. gallons (7-11 L).

The 2-minute Naval Shower:
1. Turn on water, & wet body
2. Turn off the water
3. Soap up and scrub
4. Turn water back on, & rinse
5. Turn water off
I second that. It used to drive my father (the ultimate water miser on board) crazy, but I confess that I have to shower twice a day in hot weather, and I refuse to change that habit on board. Why should I not feel good when I'm supposed to be having fun? It's not a big deal if you do the Naval Shower trick -- 4 or 5 gallons a day will get you two whole showers.

Another trick when the sea is warm is to go for a swim, wash in the ocean, and just rinse off with fresh water on the swim platform. That's even less water and plus you get a refreshing dip in the sea. In warm weather, that's what I always do first thing after getting the hook down.


By the way, does anyone besides me feel awkward explaining to guests who are not sailors that they need to shower differently? They expect comfort on my "yacht" and the idea of a Naval Shower really seems strange to some people. But if they shower like they do at home, your tanks can be empty in a twinkle.

I have often thought that it be much more convenient, and besides that would help to remind people, if instead of regular shower controls like we have at home, we had a foot pedal or something which would supply water only when pressed. Anyone ever heard of such a gadget?
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Old 21-05-2009, 06:45   #10
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Taking a nice long shower is about the only luxury i have, apart from food and sleep. I dont smoke, drink, indulge in retail therapy or rich foods. Its the place i can meditate and contemplate whilst warming up when I get home from a dirty day at work or first thing in the morning when i wake up to a cold appartment, cos i dont have the heating on.

I guess i can adapt, I usually manage it in other areas but If im able to get the RO unit sorted out, I dont have to worry about it provided its not too expensive to run.

One other thing you guys might have overlooked, the latitude here is considerably cooler for much of the year than the Carolinas and Florida and for 3 months of the year its dark when getting up for work in the morning and dark again when getting home at night.

Dont know if i would want to go skinny dipping in the dark !!
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Old 21-05-2009, 07:09   #11
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... One other thing you guys might have overlooked, the latitude here is considerably cooler for much of the year than the Carolinas and Florida and for 3 months of the year its dark when getting up for work in the morning and dark again when getting home at night.
Where is "here"?
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Old 21-05-2009, 09:02   #12
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"Here" is 51N UK

Currently experiencing record tornados, heavy thunder showers, torrential rain and moderate wind with rather hot sunny spells amongst the cold snaps

Four seasons in one day doesnt even start to cover it. Its a public holiday weekend coming up and I dont know whether to pack a bikini or winter clothes.

Probably both.
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Old 21-05-2009, 09:24   #13
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Quote:
Originally Posted by anjou View Post
I used to live in a 23' trailer on a farm with no electric or running water and I would wash in the river, even in winter, but that was 26 years ago.

AS luck would have it, a friend on an energy renewables forum, came across a RO system in a dumpster out back of a launderette and once i mentioned im looking, he messaged to let me know he has the unit but its unsuitable for his earthship housing needs.

I need to check it out but he described it as:-

3 x 20" containers, which have 1 particulate filter (spun/woven type) and two carbon filters (one is plain carbon the other I think is a carbon plus chlorine etc filter)

3 x 10" containers, each of which has an RO membrane which seems to be made up of rolled rubber-type membrane.

1 x 24v boost pump, + 1 pressure sensor.

The way I understand it, the routing was in the following order:

Water supply
particulate filter
pump
carbon pre-filter
3 x RO membranes
carbon post filter (though some systems have this ahead of the RO membranes)

Maybe this will do the job?
Can you post a pic of this find?
Sounds more like a fresh water RO system than a salt water RO unit.
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Old 21-05-2009, 10:03   #14
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Sadly i dont have a pic of the unit.
Im sure you may be right about it being a fresh water unit as it was found installed inside a large GRP tank that was cracked and therefore in the dumpster.

I will make some enquiries, is there a good way to check what type it is?
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Old 21-05-2009, 11:07   #15
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What would be the difference in an R/O membrane for a salt water system or a fresh water system?
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