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Water Tank Size & Location


TomIre

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Hi All,

We're in the design stage of a new build narrowboat with our builder! Exciting times.

They're specifying a 125 gallon/470 liter tank. We've asked for one quite a bit larger. 600 to 1000 liters. We plan to CC and it seems to me that water capacity is going to be the limiting factor for staying out.
They're struggling with finding a place for that larger tank.
So, those of you who have a larger tank - where is it?
My only thought at this point is to raise the well deck by a few inches to accommodate it. But, I think that might possibly make entry through the bow doors an issue.
Any other thoughts?

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We had a (approx) 1000 litre tank in the bow. It was actually formed by the V of the bow and the base plate with a 'bulkhead' forming the 'back-wall'.

The top (lid) of the tank was level with the gunwales with a lift-up lid for easy access for filling or cleaning.

We had a sunken well deck so the tank was actually forward of the deck flooe and did not affect the entry to the doors.

 

You will need to consider the weight / ballast as you will be adding another half-tonne right on the bow.

 

IMG-1541.jpg

 

 

 

 

Edited by Alan de Enfield
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Thanks!  Did you have a bow thruster?  Any other storage in the bow?

We are a gas free hybrid so the space is available but we are currently planning on a bow thruster and bike locker in the bow. 

I know everything is a compromise in this regard. We may have to rethink the bike locker. 

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21 minutes ago, TomIre said:

Thanks!  Did you have a bow thruster? 

 

Wash your mouth out.

No body admits to having a 'sissy-button', you will become unable to steer the boat without it and the day it fails you will be in mess - learn to steer your boat correctly and you'll manage pefectly well without one.

 

They make a teribble noise, they sound like a swarm of bees coming down the canal and you just see the boat zig-zagging from side to side.

T'aint right, T'aint normal. T'aint required.

 

What sort of toilet are you planning ?

Edited by Alan de Enfield
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Most boats these days have freestanding plastic or stainless steel tanks, most often under the well deck floor. But the usable capacity is quite a lot less than if you go for an integral steel tank in the same space. The downside with an integral tank is the need to get indside it to derust and paint it periodically.

No reason why an integral tank couldn't occupy the forepeak and under the well deck floor if you wanted to.

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8 hours ago, TomIre said:

 

We will have an electric incinerator toilet so no water required for it. 

 

 

I assume that you are having a separate diesel generator fitted to power the loo and cooking. If not please make sure your power audit and charging calculations/proposed regime is adequate.

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I assume you're planning to have Lithium batteries then. 

I don't know how much not flushing saves but you might find stopping every couple of days to top up the water tank is preferable to running the engine to replenish batteries

 

ETA cross posted with @Tony Brooks and @Jen-in-Wellies

Edited by George and Dragon
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Is this your first boat? Without wishing to appear unkind I suggest you stop watching Vlogs and start talking to boaters that have been on the cut a few years….either on here or even better on the cut…..reinventing the wheel never works well on a boat…there is a reason things evolve slowly. 


For the water tank I’d suggest an integral tank in the bow…but using a suitable epoxy coating. Make it the full height of the bow locker with decent access. Not under the well deck. 
 

As others have said think long and hard about how you are powering & heating the boat….think about being frozen in unable to get to a diesel pump. 

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5 minutes ago, frangar said:

Is this your first boat? Without wishing to appear unkind I suggest you stop watching Vlogs and start talking to boaters that have been on the cut a few years….either on here or even better on the cut…..reinventing the wheel never works well on a boat…there is a reason things evolve slowly. 

 

 

I would also suggest that you spend some time assessing the background and areas of competence of the people on here who can offer you unbiased advice based on long experience and which WILL be dissected and challenged by others. That way you get to understand what is more likely to work in the long term.

Edited by Tony Brooks
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9 hours ago, David Mack said:

Most boats these days have freestanding plastic or stainless steel tanks, most often under the well deck floor. But the usable capacity is quite a lot less than if you go for an integral steel tank in the same space. The downside with an integral tank is the need to get indside it to derust and paint it periodically.

No reason why an integral tank couldn't occupy the forepeak and under the well deck floor if you wanted to.

The boat I'm having built has the water tank in the bow like Alan's, except it's stainless steel not built-in. I have a tug bow not a well-deck and the bow thruster (boo, hiss!!!) is under the wardrobe at the front end of the bedroom (reverse layout) not under the tank, which means the tank can extend to about 6' back from the stem so it's fairly big because the hull is a lot wider than in the pointy bit.

 

There is a loss in capacity and I had a long talk with the builder (Finesse) about this, who have a strong preference for s/s tanks in general but especially in this location. Apart from the obvious reason, they gave several less obvious ones:

 

1. No need to derust/descale/repaint the inside periodically (the obvious one) -- the job is horrible and access through a small hatch to do a good job is difficult

2. Getting good epoxy cover in the first place here is tricky, there are a lot of weld seams and steelwork in this part of the hull which makes removing all the rust/scale before painting harder, increasing the chance of corrosion under the paint.

3. Unlike a tank under the well deck which sits entirely below the waterline (above freezing), a large part of a bow tank is above the waterline, which increases the risk of freezing during a cold winter. With a s/s tank you can have sprayfoam insulation between the tank and hull round the sides, the bottom of the tank is kept above freezing though the hull.

 

None of these are absolute killer reasons for an integral tank, just things to be aware of.

 

The downside of s/s is increased cost, especially since the tank is a funny shape which needs more cutting and welding. In my case (no well deck) this is made worse by the fact that the tank has to come in after the shell is built through either the side or rear doors which would limit the size, so there will actually be two tapered tanks side-by side. I'd rather pay the extra cost to avoid the issues mentioned above, others may feel differently.

 

The OP wouldn't have this problem, but would still probably end up with two tanks, a tapered one in the bow and a flat one under the well deck -- and needs to find space somewhere for the bow thruster, which reduces the size significantly. These are normally fitted vertically above the tunnel (avoids stress on the seal to the tunnel with horizontal BT mounting, not recommended), which means stealing space from the bow tank, which makes it rather small -- and there need to be gaps of several inches around the BT tunnel to allow it to be welded in and painted afterwards, further reducing tank space.

 

As also pointed out, getting on for half a tonne of water in the bow will also make a significant difference to the boat trim between full and empty, which needs to be allowed for when ballasting it.

 

There are a lot more practical things to think about than the immediately obvious ones...

Edited by IanD
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10 hours ago, Alan de Enfield said:

 

Wash your mouth out.

No body admits to having a 'sissy-button', you will become unable to steer the boat without it and the day it fails you will be in mess - learn to steer your boat correctly and you'll manage pefectly well without one.

 

They make a teribble noise, they sound like a swarm of bees coming down the canal and you just see the boat zig-zagging from side to side.

T'aint right, T'aint normal. T'aint required.

 

What sort of toilet are you planning ?

I did, I have a tug deck and the water tank sits behind the thruster tube, I still have room for a double bed on top of the tank under the well deck. I would suggest sitting down and chattind with the builder. Maybe a base plate to gunwale  height  right across the boat directly behind the bow locker

image.png.f1acb38219056329c63148ed4736ac14.png

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Hi Tomire, ours is a stainless tank under the front deck, 550 litres. Personally I wouldn't want an integral tank for pretty much the reasons given previously by IanD. Our tank lasts two of us at least a week but we can easily double that if we are just a bit mindful of our water use. Best of luck with the boat. 

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48 minutes ago, ditchcrawler said:

I did, I have a tug deck and the water tank sits behind the thruster tube, I still have room for a double bed on top of the tank under the well deck. I would suggest sitting down and chattind with the builder. Maybe a base plate to gunwale  height  right across the boat directly behind the bow locker

image.png.f1acb38219056329c63148ed4736ac14.png

Works with a tug deck, but if you have a well deck like the OP it pushes it back a couple of feet ("thickness" of tank) and shortens the cabin by the same amount. Since you only gain the volume above well deck level, anything less than a couple of feet isn't really worth it...

6 minutes ago, MichaelG said:

Hi Tomire, ours is a stainless tank under the front deck, 550 litres. Personally I wouldn't want an integral tank for pretty much the reasons given previously by IanD. Our tank lasts two of us at least a week but we can easily double that if we are just a bit mindful of our water use. Best of luck with the boat. 

Do you have a BT, and if so, where? Almost always takes a big chunk out of tank volume... 😞

Edited by IanD
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9 minutes ago, MichaelG said:

Hi Tomire, ours is a stainless tank under the front deck, 550 litres. Personally I wouldn't want an integral tank for pretty much the reasons given previously by IanD. Our tank lasts two of us at least a week but we can easily double that if we are just a bit mindful of our water use. Best of luck with the boat. 

We manage about 4 days for two of us. Maybe we drink too much tea or have too many showers

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If you want a big tank then an epoxy painted integral tank is the way to go.

You can get right inside a big tank to do any maintenance so that removes their main disadvantage.

They don't freeze in winter (remember that -15 spell about 11 years ago????)

My biggest concern with most stainless tanks is that it's a nightmare to get them out so you cant maintain the steelwork behind them, and in many cases hidden condensation can form there.

1000litres does change the trim of a boat as it empties but its not a disaster, at least not on a 70 foot boat.

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2 minutes ago, dmr said:

If you want a big tank then an epoxy painted integral tank is the way to go.

You can get right inside a big tank to do any maintenance so that removes their main disadvantage.

They don't freeze in winter (remember that -15 spell about 11 years ago????)

My biggest concern with most stainless tanks is that it's a nightmare to get them out so you cant maintain the steelwork behind them, and in many cases hidden condensation can form there.

1000litres does change the trim of a boat as it empties but its not a disaster, at least not on a 70 foot boat.

From working Offshore I would suggest that an integral tank epoxied from new shouldn't need any more treatment for 10 years 

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1 minute ago, dmr said:

If you want a big tank then an epoxy painted integral tank is the way to go.

You can get right inside a big tank to do any maintenance so that removes their main disadvantage.

They don't freeze in winter (remember that -15 spell about 11 years ago????)

My biggest concern with most stainless tanks is that it's a nightmare to get them out so you cant maintain the steelwork behind them, and in many cases hidden condensation can form there.

1000litres does change the trim of a boat as it empties but its not a disaster, at least not on a 70 foot boat.

 

Hence the sprayfoam (on the hull, see my post), just like everywhere else in the boat. Tank never needs to come out, just like everything else in the boat interior.

 

I do agree that an epoxy painted integral tank gives more volume, but as usual there are pros and cons on both sides, the OP needs to decide on which matter most -- their builder may also have some opinions, as mine did 😉

1 minute ago, MichaelG said:

No bow thruster. The stainless tank is just square and not tailored to the shape of the space so a lot of potential capacity lost. Down to cost I would presume.

Presumably, I know my solution will cost more. Adding a BT loses a lot more capacity, with one you'd probably be down to under 400l which is really too small...

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7 minutes ago, ditchcrawler said:

From working Offshore I would suggest that an integral tank epoxied from new shouldn't need any more treatment for 10 years 

Maybe, though some people have reported less. One in the bow (not a nice rectangular one) has a lot of nooks and crannies which make it harder to stop subsequent corrosion under the epoxy.

 

That's not theoretical speculation, that's coming from someone who has built several hundred hulls and used to use epoxied integral tanks, but hasn't for the last 5 years -- especially in the bows -- for the reasons I gave... 😉

Edited by IanD
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11 hours ago, TomIre said:

Bow thruster probably a discussion for another day!

 

🧡💗

 

No discussion necessary.... if you want one, get one..... end of.

 

You will find it extremely useful when reversing, amongst all of it's other uses.

 

I don't have one and can confirm that a boat can be managed very well without one, but there is no doubt it would be handy when reversing, (something I do regularly, and am good at :) )

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