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Old 03-02-2015, 22:17   #1
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How much water do we need?

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!
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Old 03-02-2015, 22:35   #2
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Re: How much water do we need?

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Originally Posted by tmoandj View Post
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!
That's not much output and its unlikely you'll be able run it all day - if you're running it from solar you can have about 6 hrs / day useful power if you're in a sunny area...that would give you only just over 30 litres a day. I doubt that will be enough for a family of three, unless you were extremely frugal.

On our last boat we had a watermaker that drew 8A and produced 30 l/hr. We ran that about 2 hours a day for the two of us and it was enough for showers, washing, cooking....we tried to keep our tanks full all the time.
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Old 03-02-2015, 23:23   #3
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Re: How much water do we need?

Others will come in but whilst a cheap watermaker it will struggle to provide enough water.

Most always upgrade to a higher capacity watermaker.
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Old 04-02-2015, 01:23   #4
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Re: How much water do we need?

spend $100 on a rain catcher and some water containers for the cockpit, it rains every day in the tropics..............
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Old 04-02-2015, 02:58   #5
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Re: How much water do we need?

Two of us aboard and we use somewhere in the order of 60-70 litres per day. Call it 65l which is around 17usgal. That's for drinking, cooking, washing up and a hot shower each.

Wife is a handwash junkie and loves a shower but I knew that before we set out so installed as high capacity Watermaker we could afford. I didn't want to be constantly thinking about having enough water. Sure we could use less but we live here full time. Before we started cruising we watched a husband and wife lugging jerry cans full of water down the beach to their dinghy and thought bugger that!

We ended up with one of the Cruise RO 30 gal/ hr models that we run from the 2kva honda Genset. We run it every 3 days for 1.5-2 hrs to keep the tanks topped off. Couldn't be happier so far.

I spent quite a bit of time working out which way to go for us. Basically needed to consider all the boat systems and energy needs and what our priorities were. Got an energy budget done early on a spreadsheet so I could easily model various options. Recommend that as a first step.

A hot shower was a must have for the wife (and it is pretty damn good I must say). I didn't want to be running the main engine for battery charging or water heating. Gas water heating was problematic. We wanted a small Genset aboard anyway.

Settled on upgrading the solar which totally takes care of our battery charging and went with a bit bigger Genset. That runs a 6 gal 1500w electric hot water heater for half an hour a day during shower time then every 3 days for a couple of hours for watermaking. Whenever the Genset runs we charge laptops, iPads, phones etc however we can charge all those from 12v.

So far so good and pretty happy with our setup. You will never have too much water or too much power!

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Old 04-02-2015, 03:11   #6
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Re: How much water do we need?

Quote:
Originally Posted by tmoandj View Post
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!
In reality, only you can answer the question "how much water is enough?" As someone else mentioned, the watermaker you have will probably only be producing 6-8 hours per day so figure 9-12 gal.

Think about your habits - will you have a salt water rinse system in the kitchen? Cuts down a lot on fresh water usage. Will you be using a solar shower? Meaning get some salt water shampoo, and wash in the sea, then a quick trip under the solar shower to rinse off the salt.

How will you do laundry while at sea? BEst way is a mesh bag. Throw your clothes in it and trail it behind the boat for a couple of hours. Haul in, dump in a bucket with some fresh water and rinse the salt out.

Think about your water usage today - Americans in general (note the in general) use unbelievable amounts of water compared to europeans. Try using only 4 gallons of water per day per person at home - can you do it?

If not - then you better start thinking about a bigger watermaker or about changing your habits.
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Old 04-02-2015, 04:18   #7
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Re: How much water do we need?

A lot of people don't have water makers. I have 2x 5 gallon containers for storage, but could get by on just one.
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Old 04-02-2015, 04:47   #8
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pirate Re: How much water do we need?

The amount of water you NEED psychologically is around 5litres/day.. that's enough for drinking/cooking and one litre every other day is enough to rinse off after a saltwater shower..
Physically you can get by on 1/2liitre/day for a longggggggg time.
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Old 04-02-2015, 09:28   #9
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Re: How much water do we need?

As a liveaboard 50gal lasted me 3/4 weeks. On passage did 2 of us for a month crossing the Atlantic (no we did not get any usefull rain!). Water is like money, you use what you have and tend to want more. A pressure salt water system to galley, washdown and deck shower helps a lot
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Old 04-02-2015, 10:20   #10
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Re: How much water do we need?

Lugging water gets old really quick.

A too small watermaker is a teaser.

A larger watermaker takes more power per hour, yes, but it produces more water.

You have to do the math: X gallons per hour at Y amps = Z amp hours.

You'll find a larger watermaker uses LESS amp hours in total for the larger amount of water.
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Old 04-02-2015, 10:41   #11
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Re: How much water do we need?

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Originally Posted by Stu Jackson View Post
You'll find a larger watermaker uses LESS amp hours in total for the larger amount of water.
Up to a point - then it turns the other way again. Not taking energy-recovery systems into account, that point seems to be 6-8gph or so.

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Old 04-02-2015, 10:46   #12
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Re: How much water do we need?

Good point, although 6-8 is still much larger than their 1.5.
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Old 04-02-2015, 11:05   #13
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Re: How much water do we need?

Two aboard can make do with 50 gallons per week... but you wont be showering a lot etc. Just cooking and rinsing off after swimming.
If the Powersurvivor is old I would consider it "no value" as it's pretty likely the membrane is shot....if the unit works at all. If it's pickled... which it very well might not be, then usually it wont get tested in a survey (unless you want to pay to get it pickled again).
Bottom line is, don't buy a boat because it has an old watermaker and especially a powersurvivor 40.
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Old 04-02-2015, 16:48   #14
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Re: How much water do we need?

Quote:
Originally Posted by tmoandj View Post
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!
We tried cruising with one and it didnt work for us. I detailed the reasons here:

Gear Review: Estrellita’s Watermaker Saga ~ SV Estrellita 5.10b

Just one boat's perspective...we use about 5 gallons per day total for two of us...YMMV
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Old 04-02-2015, 16:58   #15
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Re: How much water do we need?

[QUOTE=Cheechako;1741436]Two aboard can make do with 50 gallons per week... but you wont be showering a lot etc. Just cooking and rinsing off after swimming.
If the Powersurvivor is old I would consider it "no value" as it's pretty likely the membrane is shot....if the unit works at all. If it's pickled... which it very well might not be, then usually it wont get tested in a survey (unless you want to pay to get it pickled again).
Bottom line is, don't buy a boat because it has an old watermaker and especially a powersurvivor 40.[/QUOTE]

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