# Freshwater to seawater ratio



## TSOJOURNER (Dec 16, 1999)

Here's a question that occured to me while planning my escape. Let's say you are offshore and the watermaker goes south or water is short for any other unplanned event. How much seawater can be added to fresh to extend it without causing serious harm?
Jeff


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## sailingdog (Mar 19, 2006)

I'd say it depends on your health, the state of your kidneys and liver, the salinity of the water, the temperature, and a few other things... 

Someone with compromised kidneys may not be able to drink as high a percentage of salt water as someone who is perfectly healthy. Some one with high blood pressure probably would have problems with vastly increasing their salt intake as well. 

The saltier the water, the less you would be able to add by volume. In hot weather, your tolerance for salt water probably goes up, since you tend to lose salt via perspiration. 

I'd imagine that the duration of the ordeal would make a difference as well. The shorter the period of time, the higher the salt water percentage could be. 

My advice is try like hell not to get into such a situation. Carry spare parts and if your watermaker is only power driven.... you might consider investing in a small hand-operated one. Relying on a watermaker, on a small boat, where the electrical and other systems aren't redundant and very vulnerable to failure is a bad survival tactic. You should generally carry enough water to get you to the next port in the case of a watermaker failure. If you're convoying with other boats, this may not be as necessary, but if your on your own... I'd consider it prudent.


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## Valiente (Jun 16, 2006)

It's why I'm going to incorporate a rain-catching design into my bimini. I don't want a watermaker for the boat, but I want a hand-operated one for the liferaft...absolutely!


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## sailingdog (Mar 19, 2006)

Catching rainwater is a great idea, and many have used it...but you need to make sure you have the proper equipment to filter and treat it so that it is potable.


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## velero (Dec 19, 2001)

How many ppms of salt or total dissolved solids (TDS) are you getting from your RO system? Do you have a TDS meter? Use this simple formula to perform calculate the volume needed to reach the desired concentration.

V1xC1 + V2xC2 = V3xC3 V = Volume C= Concentration, 
V1 + V2 + V3
or V2 = ((C3-C1)x V1)/ (C2-C3)

If you have 50 gallons of water from your water maker @ 600 PPMs TDS, V1 and C1.

Your will be using salt water usually 35000 ppms, C2
C3 (lets say 1500) is the desired concentration PPMs of TDS of your total V3 volume

Yan can add 1.34 gallons of sea water to your tanks get 1500 vs 600. not wother the effort in my book.

According to World Health Organization (WHO): "The palatability of water with a TDS level of less than 600 mg/litre is generally considered to be good; drinking-water becomes significantly and increasingly unpalatable at TDS levels greater than about 1000 mg/litre."
​
PPMs = mg/liter

I looks like if it has too much salt it will no be palateble and you would not be able to dink it. On my previous job our standart was less than 1000 for long term (more than 1 week) and 1500 for short term (less than 1 week) 
Velero


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## cockeyedbob (Dec 6, 2006)

Bob's thirsty, now where did he put his calculator?

Why, in planning his escape, Bob intends to include a few jugs of fresh water, you know, just in case the r/o goes south. Float nicely behind the life raft they do, just remember to attach 'em with a length of line. 

Supplement with sea water if you must, however, if you go nuts that's probably too much so adjust accordingly.

Rainwater and bird ****, essential vitamins and minerals ...

Christ Almighty, maybe you just better be safe and stay at home.

Valiente ... you one savy hombre!


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## sailaway21 (Sep 4, 2006)

The Pardey's have written on methods of collecting rain water, rather extensively and ingeniously. You can filter it with a coffee filter if you like. The only treating you'll need to do is the chlorination of your tanks that you would normally do for offshore sailing.
Rain water is going to be more pure than any water you are likely to get anywhere in the world, even after it's run down your sails. Water purity becomes an issue when water is stored in tankage. Stored water allows bacteria to grow, a slight dose of chlorine nips it in the bud.


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## sailingdog (Mar 19, 2006)

While rain water may be relatively pure, it will also have airborne contaminants in it... IMHO, it will need more filtering than a plain old coffee filter. It will have dust, mold spores, airborne chemicals, and other such things in it... If you want to drink them, be my guest... but I prefer not to.


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## tomaz_423 (Feb 5, 2006)

Wanabe: 

If you are close to shore you go to first pub and order water (or beer). Problem solved.

If you are far away from shore the air pollution is lower than in any urban area. You just have to let go the first shower to clean the air a little (it also washes the sails and the deck), then you are better off drinking rain then not to drink at all.
There are millions of people in the world drinking rain water. (Some get sick). 
If you are on a boat you can boil that water to make it safe. 
If you run out of gas you can make solar cooker from Alu foil and some other stuff you find on a boat (lots about solar cooking is available on the web, so get educated as part of good seamanship, you never know when you run out of gas.)
If you are in a raft your chances are limited. But better to drink rain water than sea water, Sea water will kill you in no time.
(if you had a survival hand operated water-maker you would not start this tread)
Coffee filter is a joke. Large particles of dirt are most likely not your worst enemy. Boiling water is the right way to go or proper filtering - some boaters equip their boats with good filters anyway to filter questionable water you get in marinas/gas stations. Chemical treatment is good too.
I have a portable carbon filter advertised to do the job - but I would prefer not to rely strictly on it - would boil as well.
Where I leave we have some rural areas where houses collect rainwater from the roofs and not long ago they used it for drinking. And most survived.
Now the only use it for watering the garden or wash the car and for washing machines (excellent as it contains no limestone). Even when I was a kid we drank it in some cottages in the mountains.


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## cockeyedbob (Dec 6, 2006)

sailingdog said:


> While rain water may be relatively pure, it will also have airborne contaminants in it... IMHO, it will need more filtering than a plain old coffee filter. It will have dust, mold spores, airborne chemicals, and other such things in it... If you want to drink them, be my guest... but I prefer not to.


Aye dog ... that rainwater is going to be full of the very contaminents you breath ... Bob agrees, you just can't be too careful ... TIC!


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## SimonV (Jul 6, 2006)

survival hand operated water-makers leave a residue salt content between 2.6% and 4.8% this is apparently exceptable.


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## cockeyedbob (Dec 6, 2006)

Nonetheless, any port in a storm.


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## Boasun (Feb 10, 2007)

cockeyedbob said:


> Aye dog ... that rainwater is going to be full of the very contaminents you breath ... Bob agrees, you just can't be too careful ... TIC!


I am breathing contaminents!!? Oh me oh my, Tigers, Lions and Bears....
Oh what am I going to do??
Heh heh heh!

Seriously:
Have you ever been off of the coast of Los Angles?? And look toward the coast?.... A sickly brown atmosphere is all you can see there. Talk about breathing contaminents. Live there for awhile


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## Boasun (Feb 10, 2007)

For water
Use your sail or Bimini top to catch rain... 
Use a solar still to make water
use those Survivor water makers that are out on the market. A good way to have water on hand.
sail the Great lakes... and it would be: Water, water everywhere and many a drop to drink. Okay so I skewed that line from the Ancient Mariner. But you may want a carbon filter for the G.L. waters.


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## trecksail (Dec 2, 2004)

Has anyone ever seen the inside of a municipal water line that's been in use even only 5 or 10 years? If you haven't, you don't want too. Very, very nasty. Then there's the reality that all but very few municipalities have probably at least 25% of their delivery systems 40 to 50 years old. Most of the water delivered runs through the older bigger stuff at some point on it's way. 
I would drink what rolls off my sails anyday before drinking any municipal water supply.


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## cockeyedbob (Dec 6, 2006)

Seriously:
Have you ever been off of the coast of Los Angles?? And look toward the coast?.... A sickly brown atmosphere is all you can see there. Talk about breathing contaminents. Live there for awhile

Aye Boasun, I did, 11yrs Moreno Valley, 1yr San Diego ... hack hack cough ...


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## hellosailor (Apr 11, 2006)

Seriously, I've been told that the bowels are capable of absorbing fresh water while rejecting salt, and that salt water enemas can contribute a large amount of fresh water by allowing the bowels to absorb it.

Something to add to that real short list of "Fun New Things To Do While Stuck on Desert Island", in case you are also the Entertainment & Morale Officer aboard your vessel.


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## sailingdog (Mar 19, 2006)

HS-

I really don't want to know why you're researching saltwater enemas...


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## hellosailor (Apr 11, 2006)

SD-
You mis-assume that I am.
I'm simply repeating a comment by an alleged RN elsewhere who was saying what could be done to help keep you hydrated in emergency conditions.
Like I said, "Seriously."


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## cockeyedbob (Dec 6, 2006)

Yes, read that also. A quick trip to the bookcase provided the answer. Survive the Savage Sea by Dougal Robertson, Sheridan House, 1973, page 94.

Well, I suppose it would help pass the time ...


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## sailingdog (Mar 19, 2006)

hellosailor said:


> SD-
> You mis-assume that I am.
> I'm simply repeating a comment by an alleged RN elsewhere who was saying what could be done to help keep you hydrated in emergency conditions.
> Like I said, "Seriously."


I believe you... yeah, right..


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## Valiente (Jun 16, 2006)

cockeyedbob said:


> Yes, read that also. A quick trip to the bookcase provided the answer. Survive the Savage Sea by Dougal Robertson, Sheridan House, 1973, page 94.
> 
> Well, I suppose it would help pass the time ...


Talk about the eye of the storm.


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## cockeyedbob (Dec 6, 2006)

You would prefer ... cribbage?


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## bestfriend (Sep 26, 2006)

Must I say it? 
What doesn't kill you, makes you stronger. Go eat some dirt ad wash it down with a nice glass of rain gutter water.


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## cockeyedbob (Dec 6, 2006)

I read a yogi can ingest, if that's the correct word, liquids rectally using muscle control although it takes years of dedicated study.
Hell, as a kid, Bob did the same thing with the seat of a high velocity Oldsmoble and it took only a second or two to learn!

Nonetheless, saltwater enema, a worthwhile bit of survival info to file away ... might save a life. Ya never know.


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## Freesail99 (Feb 13, 2006)

cockeyed bob said:


> Nonetheless, saltwater enema, a worthwhile bit of survival info to file away ... might save a life. Ya never know.


Water skiing again ?


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## cockeyedbob (Dec 6, 2006)

Naw, just gettin' a drink.


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## sailaway21 (Sep 4, 2006)

I only meant the coffee filter to get the chunks out. (g)
You can't do much better than rain water. NYC drinks rain water, from reservoirs upstate. Grand Rapids, MI pumps their drinking water out of Lake Michigan. In both cases, it is what they do afterwards to it that makes it unpalatable.

Since the OP was interested in survival, I would expect that, if in that situation, he'd probably be quite pleased with rain water. I'd sure want a gulp of something while rigging up my saltwater enema.(G)

I am a water well driller and I always chuckle when people, usually women, see me drinking water being pumped directly from their well. They, with a superior tone of voice, announce that they only drink bottled water. I've given up on trying to explain where that comes from.


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## Valiente (Jun 16, 2006)

sailaway21 said:


> I am a water well driller and I always chuckle when people, usually women, see me drinking water being pumped directly from their well. They, with a superior tone of voice, announce that they only drink bottled water. I've given up on trying to explain where that comes from.


You mean the municipal tap, minus the chlorine? If it's more or less clean, bottlers don't have to melt a glacier...they can dig a hole downhill from the town dump.


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## SimonV (Jul 6, 2006)

hellosailor said:


> Seriously, I've been told that the bowels are capable of absorbing fresh water while rejecting salt, and that salt water enemas can contribute a large amount of fresh water by allowing the bowels to absorb it.
> 
> Something to add to that real short list of "Fun New Things To Do While Stuck on Desert Island", in case you are also the Entertainment & Morale Officer aboard your vessel.


Gees, I'm thirsty pass the bilge pump.


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## sailaway21 (Sep 4, 2006)

Val,
You got it. and sell it for more than gasoline!


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