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Old 20-02-2017, 02:48   #61
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Re: Gravity tank for fresh water - any experience?

It is something to consider, definitely. The thing is - gravity tank comes in anyway as an empty space in this area, so I'm not building anything new. It will be covered as a matter of fact in epoxy sheathing with one layer of glass as a matter of fact as well. So the only extra job I do is painting it with above mentioned tank lining (circa £20) and connecting a flex hose from the bottom to the tap. Not very laborious really, and not too costly.
For main tanks will not be connected to that one.

Electrical pump is a no. Two foot pumps - ok, effective, third in spares and should be reliable as well. But I'm complicating a system having to do all the plumbing from tanks and between them and these are other possible (however unlikely) points of failure. Hand pump - it is already in place so saving expense on one pump - still need a spare but that is even less complicated machine than foot pump and still need plumbing.

So not really, it is not cheaper to use foot/hand pumps, but I may say you have a point with an "overreaction". Just a little.

I may as well consider putting a 25l jerry can UNDER the sink and use existing hand pump to draw water from such a day tank. It answers your point about weight high above (2ft max - really that high for 13 ton boat?) waterline and my principle of a separate day/week tank. The only problem is that this is pretty useful storage space, while it leaves hardly accessible locker up there.

I don't know. If I would have made my mind about that I would not bother asking you all about your opinions. Many of you made valid points and even if I may disagree in opinion about them it helps me decide - so keep commenting. I really appreciate your help. I want simple and "bulletproof" approach as I explained in posts above. It must last a year with giving me too much grief.
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Old 20-02-2017, 03:02   #62
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Re: Gravity tank for fresh water - any experience?

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No, in this case several items will move downwards. Including 100l of diesel - it is why I'm getting the space for lockers (and gravity tank) in first place.

My two fuel tanks live very high now, just under cockpit sides. Not sole, not even seats - sides. I'll move them good 3ft downwards and probably replace with PE ones (now I have steel ones). In total it will get probably more weight off the boat (not mentioning remainder staying much lower) than the whole gravity tank will weight when full.
I can't help myself...were the fuel tanks originally gravity fed and now will need an electric pump because they were lowered?
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Old 20-02-2017, 03:07   #63
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Re: Gravity tank for fresh water - any experience?

We installed a gravity tank in our 28 footer under the cockpit seats on one side. New battery bank in similar, but slightly lower on the other side. Tank takes 90litres but keep far less than that in it. If having a weekend on Sydney harbour or further afield maybe a little more. Yacht displaces 8 tonne so not really a weight problem. Would have liked to install lower bur nowhere to place it. I presume that original tank was in forepeak but holding tank is there now and there was no water tank when boat was bought. Certainly no discernible impediment to boats performance. Gravity feed is really good and simple.
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Old 20-02-2017, 03:07   #64
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Gravity tank for fresh water - any experience?

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I can't help myself...were the fuel tanks originally gravity fed and now will need an electric pump because they were lowered?

No, fuel tanks will be still OVER the engine, I'm not going to loose gravity feed for my engine. But they are ridiculously high now and with 100l of diesel plus heavy metal tanks - that is something to consider in terms of weight even on my boat
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Old 20-02-2017, 04:39   #65
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Re: Gravity tank for fresh water - any experience?

I think your desire for a reliable, simple system is sensible, as is the wish to preserve water.

I don't quite agree with your choices to achieve these aims, but it's not my boat, it's yours .

Another sensible aim is to make offshore sailing in rough conditions as easy as possible. This is especially important in a small boat when sailing solo. Simple jobs like making a cup of coffee become a lot more difficult when the boat is bouncing around, you are trying to preserve night vision and are cold and tired. Throw in some complicating factors , perhaps lots of traffic, maybe some seasickness and you will not want extra complication or time spent down below just to fill the kettle if your gravity fed tank has run dry.

Talk of having tempory pumps, that are not installed, to fill the day dank seems to hurt rather than help reliability over a fixed installation of the same pumps. At the same time it makes life that little more difficult.
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Old 20-02-2017, 05:25   #66
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Re: Gravity tank for fresh water - any experience?

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(...) seasickness and you will not want extra complication or time spent down below just to fill the kettle if your gravity fed tank has run dry.

Talk of having tempory pumps, that are not installed, to fill the day dank seems to hurt rather than help reliability over a fixed installation of the same pumps. At the same time it makes life that little more difficult.

Good point (brainstorming such an idea works ). I may need to re-think it and maybe install (semi-)permanently a small pump with a hose getting down to the tanks. This way I can always override it getting a spare hose straight to the tank if something gets wrong.

But, on the other hand, 25l while sailing solo it is almost two weeks usage (ok, 1 1/2) so easier is just to put "filling the tank" on the checklist for heavy weather preparation. Or just keep couple of 2l bottles with water as a reserve in a cupboard under the sink
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Old 20-02-2017, 06:23   #67
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Re: Gravity tank for fresh water - any experience?

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Or just keep couple of 2l bottles with water as a reserve in a cupboard under the sink
That was going to be my first suggestion for a backup plan in case of pump failure. I actually keep a few gallon bottles (we still have those in the US) stowed in strategic locations around the boat. I'm not worried about pump failure, I keep a spare. But anything might compromise the fresh water system.
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Old 20-02-2017, 07:21   #68
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Re: Gravity tank for fresh water - any experience?

A gravity day tank is fine but you still have to fill it with plain non gravity systems so basically there is no gain in simplicity terms. You will end up with more tanks, more pipes and more taps. And the gravity fed tap will need a valve and etc.

I would stick to a plain banana low placed tank and a foot pump that sucks thru the top of the tank.

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Old 20-02-2017, 08:32   #69
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Re: Gravity tank for fresh water - any experience?

Forty years ago,when I launched my boat, I asked the same question. I built a 2 1/2 polyethylene day tank in a dead space behind some cabinets (a space that would have otherwise been difficult to access), and about two feet above the connected water faucet. I then installed a small Whale plastic bilge pump to fill the day tank from the bilge area water tank. The plan was to be able to limit potential overuse of fresh water by having to refill the gravity tank as needed. The concept worked, but over time I realized that I didn't have a problem with using too much freshwater. Forty years later, I am getting ready to install a watermaker. The day tank was removed and the dead space made more accessible using a sliding drawer/shelf. I am also going to electric pumps, having had sufficient experience to see their reliability. I also am installing foot pumps, one for fresh water, one for salt water, in consideration of Murphy's Law.
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Old 20-02-2017, 08:36   #70
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Re: Gravity tank for fresh water - any experience?

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But, on the other hand, 25l while sailing solo it is almost two weeks usage (ok, 1 1/2)
Less than 2.5L per day is low fresh water consumption.

Be careful, especially in the tropics, or with seasickness. Dehydration combined with a lack of sleep from single handing is not a good recipe for making sensible decisions.

It is important that boat systems are engineered to be reliable, sturdy and fail safe, but it is also important for boat safety that systems are designed to keep the crew performing at peak efficiency. This is especially important with only one POB.

Anyway, at least you are thinking about how systems will work best for you and your boat, which is always important.
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Old 20-02-2017, 09:00   #71
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Re: Gravity tank for fresh water - any experience?

Roy, thanks for that. It didn't make a decision much easier since you're moving to different setup but if it was good for forty years I'm not so mad after all I would not consider that probably if not for the planned voyage which will test everything (including my ability to save water) to the limit.

Noelex, I won't go below that, that is why I corrected myself. Counting 2.5l a day on average - which is plenty taking into account milk* and juices - means I still need around 860l of water. That is quite a large amount for my little boat. So I need to make sure I'm doing everything I can to make it go the whole way. I have few tricks for that. The way the water is dispensed is one of them - I just cannot decide which way is better
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Old 20-02-2017, 09:21   #72
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Re: Gravity tank for fresh water - any experience?

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Noelex, I won't go below that, that is why I corrected myself. Counting 2.5l a day on average - which is plenty taking into account milk* and juices - means I still need around 860l of water.
860l is about a year's supply at your rate of consumption. What kind of voyage are you planning?
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Old 20-02-2017, 09:34   #73
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Re: Gravity tank for fresh water - any experience?

That is 312 days plus 10 percent reserve. I'm racing my sistership from 50 years ago, Suhaili. I'm not sure if I can make it faster even with modern weather forecasting but that is something I want to check. But to stay in the race at all I have to do it without outside assistance- that is why a maybe a bit paranoid about preparations
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Old 20-02-2017, 09:43   #74
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Re: Gravity tank for fresh water - any experience?

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But to stay in the race at all I have to do it without outside assistance- that is why a maybe a bit paranoid about preparations
See my website for details.
OK, that explains the necessity for drastic conservation measures.

Good luck
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Old 20-02-2017, 16:23   #75
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Re: Gravity tank for fresh water - any experience?

Totally agree with Noelex. We have pressure water and a foot pump. I always use the foot pump for washing dishes. You develop develop a foot dither to rinse a plate completely with a tablespoon of water. Easy and fun and water saving!
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