# required fresh water for a vessel?

Discussion in 'Education' started by SeaBoat, Sep 21, 2020.

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1. Joined: Sep 2020
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### SeaBoatJunior Member

Hello Guys,

I am new here. I am currently doing a academic project about a container vessel. Can you guys please tell me how can I determine the required fresh water for a vessel? Is there any empirical formula? I would be grateful to you, if you kindly tell me the procedure to calculate this.

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### Will GilmoreSenior Member

Welcome Seaboat,

If you're talking about drinking water tanks, this might help.

How Much Water Should You Drink Per Day? https://www.healthline.com/nutrition/how-much-water-should-you-drink-per-day
"Health authorities commonly recommend eight 8-ounce glasses, which equals about 2 liters, or half a gallon. This is called the 8×8 rule and is very easy to remember."

So, with a crew of 10 and a maximum one month at sea, that would mean a water tank of .5gal x 30days x 10people = 150gal.

I would be incline to double, aboard a ship of any size, the expected requirement. However, the longer water stands unused, the harder it is to keep sanitary. It may not be desirable to have a water tank that is too large.

-Will (Dragonfly)

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### brendan gardamSenior Member

Don't ships get most of their water from watermakers?

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### TANSLSenior Member

On a passenger ship, it was normal to consider 100 liters / person-day, to take into account all fresh water consumption, not just drinking water.
If the ship has water generators or a treatment plant, the capacity of the tanks could be reduced.

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### SeaBoatJunior Member

Thank you. I got it. But what about other consumption, i.g. washroom including bath and other necessary jobs?

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### SeaBoatJunior Member

A huge consumption! Could you please tell me about fuel oil consumption or diesel consumption?

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### SeaBoatJunior Member

Interesting

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### bajansailorMarine Surveyor

Seaboat, using 100 litres per person per day is a good start - for 10 crew that is 1,000 litres per day.
Remember this is water used for everything, not just for drinking, or crew having showers.
Next, you have to decide what your endurance has to be before you have to refill your tanks.
If it is say 20 days, then you will need a fresh water capacity of 20 tonnes minimum.
Even if you have a water making plant on board, it could break down, so it is good to have sufficient capacity to undertake the longest anticipated voyage without making water on board.

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### TANSLSenior Member

All consumption must be taken into account, in addition to drinking water, water for toilets, showers, sinks, water for general cleaning, washing machines, dishwashers, ... Drinking water is a minimal part of total consumption.
Regarding the consumption of diesel oil, it is best that you consult the catalogs of the engines that you wish to install, bearing in mind that not only do you need fuel for the propulsion engines but there are several other consumers of diesel oil.

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### SeaBoatJunior Member

Great details. One more question, Could you please tell me how can determine fuel, diesel consumption?

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### SeaBoatJunior Member

Thanks.

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### gonzoSenior Member

Look at the engine consumption chart from the manufacturer. Calculate what RPM is the engine going to turn at the target speed. Multiply the value for the hours the trip lasts.

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### TANSLSenior Member

Fuel consumption does not depend on the speed of the boat. A stationary boat may be consuming a lot of fuel. On the other hand, I don't know if the OP needs to know the trip consumption or the fuel consumption / hour. Perhaps this second value is more useful than the first one.

Last edited: Sep 21, 2020
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### RAraujoSenior Member - Naval Architect

Real data from a real passenger type ship: fresh water consumption 150-200l/person/day not including drinking water (I would expect that in high-end cruise ships the consumption would be slightly higher). I don't expect the value to be very different for a cargo ship - in fact we noticed that when operating without passengers the water consumption (expressed in l/person/day) goes up...

Note that on my vessel the toilets are vacuum type thus requiring less water.

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### Will GilmoreSenior Member

You use fresh water in the head?

-Will (Dragonfly)

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