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Increased water storage

I've been thinking about solutions to increase water storage on a liveaboard vessel, to limit water refill trips. Ideally a solution would double water capacity of a standard craft, e.g up to 300 gallons).
2 scenarios:
1. Refitting an existing hull with 'normal' size water tank built into bow.
Extend existing water tank back into hull so weight is balanced on both sides of hull. Requires lots of metalwork.
2. 2nd plastic tank somehow connected to 1st. Any ideas on how to get that to work reliably? Not so keen on this approach but maybe somebody knows how this could be made to work?
2. A new build hull with an increased size water tank. Again I guess the tank could extend back into the interior of the boat.
But maybe there is a way to centralize the tank.
Or maybe the bow can be designed so the whole space can be used for water. e.g if the boat has no gas so there would be no need for gas lockers.
Just looking for an expert's thoughts.
It may well be 'forget it'!

Asked by: Paul McMahon  | 1.40pm, Monday 28 October

WW says:

All of those options are quite "doable" and have been done before. One major issue with very large water tanks is the change in trim that they can create between nearly empty and nearly full. 300 gallons of water is around 1.3 metric tons. if this was equally spread out across an average 70ft boat, that would be a difference of around 1.25 inch in trim. On a 57ft boat, that would be 1.5 inch. However, if the entire tank was in the bow, the difference in trim could be greater than 4 inches!
Central tanks can be fitted easily... and additional plastic tanks can be in series with the main water tank, especially if they are "downhill" of the main tank. Linking the outlet from the main tank say into a tank under a port berth, which is then linked under the floor to a tank on the starboard side. This tank is the one that the pump draws from, so that water is pulled from the main tank through the subsidary tanks.
The main proviso is that each tank would need its own separate air vent, and that no tank should be higher than the filling point and/or lowest breather pipe.
This approach is often done on larger vessels.
also, be aware that larger tanks need internal baffles, to stop water sloshing around when not completely filled which can have a suprisingly annoying effect on lateral trim, especially if the boat is moving lot (such as a tidal river.
polypropylene tanks are quite easy to fit and can be custom made, or bought in a wide range of sizes. They have the advantage that normally they are fitted with access hatches, so that you can inspect the interior and this can help with period cleaning and disinfection.
If we can help further, please ask!

Mark Langley  | 5.45PM, Monday 28 October

I wrote an article in the October 2007 issue of WW (pages 78 and 79) about a liveaboard boater who needed a larger water tank. His solution was to cut out the top of the front deck, remove the old rigid tank and replace it with a purpose-made flexible liner that was much bigger. The top of the front deck was then welded back into place. This is quite a radical solution that needs to be done by a competent boat yard.
The owner was delighted with the extra freedom that not needing to fill up with water so often gave him.

Graham Booth  | 12.22PM, Thursday 31 October

Readers say:

Thanks a lot for the advice.

Paul McMahon  | 10.09AM, Tuesday 29 October

That's great Graham thanks I'll take a look.
I wonder if any hull builders are considering this for new customers?

Paul McMahon  | 4.33PM, Friday 8 November

I am currently designing my own narrow boat from scratch this is one of the many important items I'm taking into consideration. Recently there was a 61ft Boat for sale at ABNB called the Kara Sea 2. Unfortunately it is now sold but it's layout and equipment demonstrated perfectly water, fuel and power consideration. It had a Josher Bow with 450 gal water tank, 85 gal propulsion diesel tank and 170 gal domestic diesel tank. Much of that line of thought I am incorporating into my own project. I still have the sale brochure PDF of the Kara Sea 2 which I could email over for you to look at. I don't know who the new owners are but they picked up an absolute bargain at £40k down originally from £70k

richardw66  | 12.25PM, Tuesday 26 November

Hi Richard, sorry for my long delay in replying but that sounds very interesting.
Could you email me the Kara Sea 2 brochure to:
mail at pwm.myzen.co.uk
But with the at bit replaced with @ and no spaces. I did that to hopefully stop internet 'robots' spamming my email address.

Paul McMahon  | 4.47PM, Monday 30 December

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