Water Maths

[nimblemotors]

I'm a minimalist kind of guy, and I am planning on having a watermaker.
Even the small ones make a lot of water for a few people, big ones just make it faster.
If you have sufficient solar and batteries at 12-24v pump,
you don't need to run the engine to make a lot of water.
The weight savings is enough to warrant it for a catamaran, and another source for water besides carrying it.
I would not have big water tanks, but have multiple smaller ones or even small separate containers.
my $0.02

[AussieGeoff]

Originally Posted by Schmacko

4. Drinking per person = 1.25L

Um, just focussing on this aspect, I'd suggest that if it's hot, you need about a litre an hour resting in the shade for the average adult to be properly hydrated. If you are walking or working, at least double that.

Climate where I am is hot and dry, probably more extreme than where you'd be, but in any temp over about 25c you need a lot more than 1.25l a day for the average adult over and above coffee etc.

Heat prostration and dehydration are insidious and can creep up on you, and it's easy to not notice you are becoming dehydrated in some circumstances.

Geoff in South Oz

[Stu Jackson]

In addition to the good comments here so far, here's what a friend of min wrote from his perspective on his trip from Vancouver, BC to Mexico:

The watermaker was a great investment. I've seen the other side - people buying their water in 5 gallon jugs and trying to sneak in a little shampoo as they steal a beachside shower from a resort. It doesn't look like fun. We love the watermaker.
Capacity is important. The cheaper low volume Katadyne units have to run forever to make enough water. Something in the 150 gpd range is much better. We have a Spectra unit.

It's an ATTITUDE and more comfortable way of life as well as the Math. he sold the watermaker for 80 cents on the dollar when he returned home. Pretty good deal if ya ask me.

[DefinitelyMe]

I'm confused as to where all these marinas and supermarkets are in the South Pacific......

Personally, i never paid for water so that cost was non-existent but i got pretty tired of lugging 5-gallon containers full of water out to the boat in the dinghy every few days when i could have been doing something more important, like figuring out which of the thousands of things you can do with a coconut sounds most appealing. All of the reasons for and against given here sound pretty reasonable. For me, i'm just lazy and a watermaker allows me to be more lazy.

The answer - do you need a water maker? Absolutely not; people have stayed at sea for years, literally, without one. Do you want one? That's up to you.

[44'cruisingcat]

We average about 35 litres of water per day, with 2 on board. We have a 30 litre/hour watermaker that uses about 8.5 amps when running. So we use about 10 amp/hours per day of solar power to give us complete freedom from having to visit marinas or lug jerrycans for water.

An absolute bargain IMO.

[colemj]

That is a good amp/gallon equation. I assume it is an energy-recovery type of unit?

Mark

[44'cruisingcat]

No, it's a Village Marine tech Little Wonder 200 GPD watermaker.

[seandepagnier]

When I left mexico I had 50 liters of water. When I got to the cook islands (first landfall) I had 30 liters of water. When I left vanuatu, I had 40 liters of water, when I got to philippines, I had 50 liters of water. I don't have a watermaker.

Did anyone mention clipping a funnel with a hose to your mainsail at the lowest point? Works best when reefed. You can get a liter of water per second (and I'm on a 27ft boat) during squalls. If you are crossing the equator you are pretty much guaranteed to get hundreds of liters of water this way. A regular size hose might not be large enough diameter, think at least 1.5 inch for a 41ft cat.

Some people try to avoid squalls, but I try to hit them to get water and more wind which moves the boat faster. Also turning when in the squall to stay in it longer. Take your showers during squalls.

Next, upgrade your solar panels to have a small gutter around them as well as collecting all the rain that runs down the mast (quite a lot) to work all the time, even at anchor with minimal work and virtually no disadvantages.

All of the world precipitation trends are pretty well known (see my climatology plugin for opencpn which includes precipitation maps of the world for each month) You may also plan your sailing routes to include areas with rainfall.

I also have a small solar still which makes just enough water for drinking if I'm on a long stretch without water.. I only used this as a test for a few days until I reached the area of squalls, but in this way, I do not rely on precipitation.

If you are island hopping in the dry season, there is certainly free water available in most places, you can take 20 liter containers. I have an excellent sailing rig I hand sewed for my kayak which allows me to quickly reach local water sources.

Don't load your boat down with 700 liters of water, it won't sail good. 50 liters per person maximum.

[colemj]

Originally Posted by 44'cruisingcat

No, it's a Village Marine tech Little Wonder 200 GPD watermaker.

24V, correct? That makes sense - I had assumed 12V.

Mark

[44'cruisingcat]

No, it's 12 volt.

[44'cruisingcat]

Apologies ColemJ, your questions made me look up my log; haven't run the watermaker in a few months since I've been marina bound while doing the repairs on Schools Out.

The watermaker uses 17 amps, not 8.5. So around 20 amp/hrs per day. Still well worth it, IMO.

[x-ray]

We spent last year in the Med, there is hardly any rain in summer there, so catching rainwater is no option there.
Our DIY watermaker did cost us less than 2.000 USD, giving us 60 Liters/hr.
Despite the discussion about 12/24 Volt or genny-run, i just want to say, that the watermaker helped us to save a lot of money
by avoiding expensive marinas, in ports and harbours, mooring in places without electricity and water supply has been for free many times.
No need to think about where to head next only to refill your watertank....