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Old 04-02-2015, 17:26   #16
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Re: How much water do we need?

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I'm looking at a boat equipped with a Katadyn Powersurvivor 40e. It's output is 1.5gal/h or 5.7L/h drawing 4A/h. We're aiming to run the engine, well, never. So, the low power requirement is attractive. With a maximum output of 36 gallons/day or 136 litres/day it seems like it'll be enough for our little family of three but I wonder: how much is a reasonable estimate of water consumption while cruising. I'd like to have an idea of how much the thing will be running and what the cost will actually be in our power budget. Thanks everyone!
For a family of three and on a boat the size you are looking for 40' +/- the 40e is an extremely anemic watermaker. Even if it does work you will run it to death in short order trying to keep up with a family of three. Don't look at the daily rate a watermaker produces, always look at the hourly rate. 4amps for 1.5gallon of water is energy expensive.

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Old 04-02-2015, 17:39   #17
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Re: How much water do we need?

Our power survivor 35e does just fine for me and dad and as far as pickling goes there is no need if you use it every few days and the cost is neglegable to pickle it any way defender sells the biocide powder in a 210 gram bottle and only takes 10 grams in a gallon of fresh water to pickle our membrane is well over 30 years old and still working just fine. However if you do replace the 40e let me know I would like to have first crack at purchasing it from you
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Old 04-02-2015, 17:41   #18
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Re: How much water do we need?

My wife and i use as little as 8 gal / day. We budget for 12 gal / day. This includes showers and living like a normal person. Not camping.

We have a spectra watermaker and 240 gallons of water tankage.

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Old 04-02-2015, 21:06   #19
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Re: How much water do we need?

As posted the Power Survivor 40E is anemically small. I would look at a Spectra 150 (same company, Katadyn) 6.25 gallons an hour and 9 amp consumption.

Power Survivor 1.5 gallons @ 4 amps = 2.6 amps/gallon

Spectra 150 6.25 gallons @ 9 amps = 1.44 amps/gallon and a lot less time to fill the tank.
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Old 04-02-2015, 21:44   #20
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Re: How much water do we need?

Water use is fascinating, and just as varied as everything else in cruising. When we started out we had 80 gallons of tankage and that lasted four weeks with two adults and two teens aboard. That's 20 gallons/week or 3 gallons/day spread over 4 people.

Never felt too deprived, but then when they first came out we put a 40E on the boat. Real output closer to 1.25 gallons/hour under most conditions, and we ran it for 2-3 hours/day to keep up with usage.

Now, with more comforts (such as a shower) on the "need" list I would put on a higher output unit (for me, probably a Spectra/energy recovery as we don't have a generator and generally charge only from solar or wind). You mileage will vary, it all depends on how much water you use and what lifestyle you want to lead.
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Old 04-02-2015, 21:50   #21
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Re: How much water do we need?

Rough guide for water usage.

Minimum - .5 gallons per person per day. Mostly for drinking

More liberal use of water - 2 gallons per person per day

(Imperial gallons)
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Old 04-02-2015, 22:19   #22
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Re: How much water do we need?

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Originally Posted by jackdale View Post
Rough guide for water usage.

Minimum - .5 gallons per person per day. Mostly for drinking

More liberal use of water - 2 gallons per person per day

(Imperial gallons)
And if you get a BIG watermaker, you might become a progressive.
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Old 05-02-2015, 00:03   #23
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Re: How much water do we need?

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Originally Posted by mitiempo View Post
As posted the Power Survivor 40E is anemically small. I would look at a Spectra 150 (same company, Katadyn) 6.25 gallons an hour and 9 amp consumption.

Power Survivor 1.5 gallons @ 4 amps = 2.6 amps/gallon

Spectra 150 6.25 gallons @ 9 amps = 1.44 amps/gallon and a lot less time to fill the tank.
One thing I see here is most ppl are recommending getting a bigger to water maker what seems to slip the observations of most is the op stated the 40e is already installed on the vessel so to change to ,larger water maker would include a sizable additional cash outlay
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Old 05-02-2015, 00:30   #24
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Re: How much water do we need?

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One thing I see here is most ppl are recommending getting a bigger to water maker what seems to slip the observations of most is the op stated the 40e is already installed on the vessel so to change to ,larger water maker would include a sizable additional cash outlay
True, but this thread will have information that can apply to many. I was thinking briefly of the 40e for myself but quickly decided that it has not only low output but inefficient output in terms of amps per gallon.
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Old 05-02-2015, 00:50   #25
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Re: How much water do we need?

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Rough guide for water usage.

Minimum - .5 gallons per person per day. Mostly for drinking
I use 1.5-2 liters of water per day.

There is a lot of talk about watermakers, but you should keep in mind, there are a lot of disadvantages to them:

1. expensive and difficult to obtain parts for in remote places
2. frequently break down (I have met a lot of people with broken ones)
3. cannot run in polluted water which is basically every port
4. If you _don't_ run them often enough they break unless you pickle them, so it's a problem if you stay in a port too long


Now.. considering there are so many people who don't use water makers, why not consider the alternatives:

1. rainfall - I can catch 20 liters in 5 minutes with good rain.
2. solar still - I have a very inefficient inflatable one which produces 1 liter per day. If my water container has just a few liters of water left, I can use it to have enough water to drink.
3. forward osmosis - very cheap and reliable for emergency use. When combined with a small solar still, there is plenty to drink indefinitely.

4. dehumidifier - not recommended, cheap, but bulkey. Reliably produces 1 liter an hour but uses much power


I think much is to be done in the field of improving the efficiency of solar stills. A square meter unit (which would have PV cells (only 20% efficient) would use the excess heat to make fresh water) A small fraction of electricity is needed to pump salt water, and to run a vacuum pump to pump the evaporated water into the condenser (which heats incoming sea water) this would produce 10 liters of water each day.
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Old 05-02-2015, 06:45   #26
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Re: How much water do we need?

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Originally Posted by boat_alexandra View Post
I use 1.5-2 liters of water per day.

There is a lot of talk about watermakers, but you should keep in mind, there are a lot of disadvantages to them:

1. expensive and difficult to obtain parts for in remote places
2. frequently break down (I have met a lot of people with broken ones)
3. cannot run in polluted water which is basically every port
4. If you _don't_ run them often enough they break unless you pickle them, so it's a problem if you stay in a port too long

Now.. considering there are so many people who don't use water makers, why not consider the alternatives:

1. rainfall - I can catch 20 liters in 5 minutes with good rain.
2. solar still - I have a very inefficient inflatable one which produces 1 liter per day. If my water container has just a few liters of water left, I can use it to have enough water to drink.
3. forward osmosis - very cheap and reliable for emergency use. When combined with a small solar still, there is plenty to drink indefinitely.

4. dehumidifier - not recommended, cheap, but bulkey. Reliably produces 1 liter an hour but uses much power

I think much is to be done in the field of improving the efficiency of solar stills. A square meter unit (which would have PV cells (only 20% efficient) would use the excess heat to make fresh water) A small fraction of electricity is needed to pump salt water, and to run a vacuum pump to pump the evaporated water into the condenser (which heats incoming sea water) this would produce 10 liters of water each day.
1.5-2L/day of water is almost survival conditions. We live in the tropics and I drink at least a 4L/day due to sweat loss. I also enjoy fresh water showers. Good on you, but I think it is unreasonable for most people. Or at least undesired.

1. Yes, water makers are expensive, but for several of them it is dirt-simple to find almost all parts in all countries. Membranes and pressure vessels excepted, but these are rarely an issue. Most other "problems" are solved by carrying a simple maintenance kit for the pump. I leave off the fancy electronic-controlled systems here because these do always seem to be having issues.

2. Our experience with two different water makers over the past 10yrs has been that they are some of the most reliable systems on the boat. Ours have always been manual ones. Almost all water maker problems I see are automated ones - and the problem is with the automation electronics, not the watermaker itself.

3. Well, I wouldn't run them in a harbor filled with oil or chemical effluent, but they can be run in some pretty dirty places. Most cruisers avoid these places as long-term destinations. And most large harbors that may be polluted have potable water easily available.

4. Water makers do not "break" by not running them. The membrane can get fouled, but nothing breaks. Flushing them once or twice a week takes 1 minute and pickling for long term takes 15 minutes.

.
1. Rainfall. Absolutely. Everyone should maximize this capability to the extent possible. However, it doesn't rain for several months in many cruising grounds.

2. Solar still. I think you put down that argument yourself.

3. Forward osmosis. Any reasonable system of this is going to require starting with fresh water to begin with. A salt water system would require not only a complicated and large setup, but constant oversight and operation of it to produce less water than the OP's current water maker.

4. The energy required to run a dehumidifier would power a 150 Lph (100x more) watermaker that took up the same amount of space.

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Old 05-02-2015, 07:58   #27
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Re: How much water do we need?

To specifically answer the OP's two questions:

1. It depends.

2. It depends.

It depends on how much water you use, as people have pointed out, and what your energy budget actually is.

In reality, 1.5/gph is basically survival rations, meaning you can use it to eek out water independence for a very long time if you're very frugal and you have the renewable power to run it. For some, 4 amps is nothing. For others it's a considerable chunk of their budget. So it depends.

Most opt for a higher capacity water maker because a) they use more water b) they don't want to run it every day, but rather much more infrequently, and/or c) they want more efficient production. Where you sit on that spectrum is a function of personal need, wishes, and the energy infrastructure of your boat.
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Old 05-02-2015, 08:02   #28
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Re: How much water do we need?

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spend $100 on a rain catcher and some water containers for the cockpit, it rains every day in the tropics..............
+1 worked for us for 11 years
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Old 05-02-2015, 08:48   #29
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Re: How much water do we need?

Our family of 4 has been using 20-25Gals/day of water now for about 7yrs. Sure we could use 10-15/Day, heck maybe even less if we had to, but just like power, you will adjust your water usage to what you have. Now me, I couldn't survive in 90+ heat and humidity without my shower after the morning boat projects and shower before bed....but hey, I'm a water whore and love it.

As a high output water maker pusher.
  • I don't sell daily or even twice daily showers when it's hot and sticky.
  • I don't sell Deck and Gear wash downs at anchor
What do I sell?
  • Romance Aboard Baby!
Guys, if you haven't figured out that the chances for romance while cruising and living aboard are directly proportional to the cleanliness of your body, then I give up....You might as well become a monk. And NO....most wives are not going to count a salt water swim, or Hudson garden sprayer shower as really having a "clean body", so you can forget that along with your underway cockpit fling!

I've chatted water makers with a lot of cruisers and I just don't remember someone telling me "Rich, I went with too large a water maker, I should have bought a smaller one" or "I have too much solar aboard".
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Old 05-02-2015, 08:49   #30
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Re: How much water do we need?

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One thing I see here is most ppl are recommending getting a bigger to water maker what seems to slip the observations of most is the op stated the 40e is already installed on the vessel so to change to ,larger water maker would include a sizable additional cash outlay
That's true, but essentially the OP asked to find out if the one that's on the boat is adequate for their intended use. The general conclusion was that it was way small.

It's like: I am considering a boat with 1 Grp 24 battery and intend to cruise offshore without solar or an engine. Do you think I'll have enough power?
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