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Old 19-02-2017, 08:08   #16
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Re: Gravity tank for fresh water - any experience?

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Originally Posted by noelex 77 View Post
Perhaps I am missing something, but you will still need to move the water from the main tank to the gravity tank.

You could manually scoop it out, but this will be difficult when the main tank is low and it will be hard to reliably seal the main tank and still maintain easy access. So you will most likely pump it out. Using a manual pump would work fine, but I don't see the advantage over using a foot pump to deliver the water directly from the main tank to the galley.

Precisely controlling the water delivery with a foot pump, leaving both hands free, is one of the advantages of the conventional manual system of pumping water directly from the main tank. This is better than a tap if you trying to conserve water, especially in rough conditions. You would lose this with a gravity tank.

However, having a separate tank that can be filled with the best quality water for drinking is something that can sometimes be worthwhile, especially if you don't have a water maker. A day tank for water in a similar vein to a day tank for diesel.

Pretty good points there, thanks. I don't like foot pumps for some reason, don't know really why. Maybe repaired too many in my life

Your last paragraph gives an idea why I think about that. Quite a lot of my water will be in 6-8l bottles to supplement tanks, so some manual handling would be necessary anyway. Don't have and won't have a water maker so I have to monitor water AND divide water collected along the way. I'm thinking about 25l tank to have a good use of it when I'm not sailing alone, for myself it would be partially filled (1 week supply). Refitting will mean also changing water tanks to 4 separate ones totalling 600l. I think about using simple plug-in electric and spare simple manual pump to transfer water from the tank to the gravity tank without any complex (read: prone to failure) installation). Just with a use of a can

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With such a small amount of water there is no opposing pressure to prevent the water from flowing. You don't need to go as high as 2 feet unless that's the best spot to store your water.

It is. Otherwise I would have to go even lower to get under a cockpit sole and also reduce cupboards.
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Old 19-02-2017, 08:14   #17
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Gravity tank for fresh water - any experience?

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I find the poster's analysis strange. Why on earth would you build a tank when $20 or so will buy a 6 gal water jerry can? If you don't trust your electric pump or the manual backup it is a lot easier to keep a few water jerry cans on deck for backup. I'm sure he could use that space over the sink for something more useful than spare water.

As I said, I'm refitting this part of the boat anyway. And just realised I have a little space just above sink - which I can use as a storage locker with pretty difficult access or use it for something else. I was thinking about a jerry can (£4-5 in here) but it won't fit.

And jerry can on the deck doesn't help water flowing

Btw, the space is actually on the other side, over a locker behind the sink. No access from galley side, difficult access from the cockpit side (but possible when needed).

Btw2 - and "she" not "he"
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Old 19-02-2017, 08:17   #18
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Re: Gravity tank for fresh water - any experience?

Sure, it will work fine. This used to be a common installation. As regards height, 2' will work fine. You can get an idea of the pressure you will have by putting a hose in a container of water, filling the hose so that it will function as a siphon, and then holding the outlet at various distances below the container. A simple experiment that will clarify what feed pressure you will have.
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Old 19-02-2017, 08:37   #19
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Re: Gravity tank for fresh water - any experience?

If we are talking about getting water outta the main tank after an electrical shutdown - and why would that happen? - surely a simple hand pump inserted through the hand hole (clean-out cover) in the top of the main tank to suck out some small quantity of water, is the way to go. Pump out enough to fill your pressure cooker and put on the lid. Set the PC in the fiddles, and there you are with enuff water to see you through the day and get the electrics fixed.

Why is it even an issue?

Generally speaking, a foot operated pump by each sink is the most efficacious solution for minimizing waste of fresh water. Keep a spare pump if you are really worried about malfunctions. They are cheap and they are easy to swop out.

IMO electrics are to be eschewed, and the smaller the boat the more that is the case. Electrics are convenient, but you should always have a "work-around"

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Old 19-02-2017, 08:54   #20
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Re: Gravity tank for fresh water - any experience?

Stick to the Pardeys proven advice "As simple as possible"

I would add that a well-fitted yacht should "collect her own water and electricity".

Working notes from my design which may or may not help you....

To that end I'll eventually have gravity feed -- a modification to my current system.

Solar panels collect electrons and collect rain.
Small fixed tilt to direct the water. How many degrees to get water to move?

Eventually add a larger tilt adjustment on the three panels for better solar gain.

Water then spills forward from panels onto fixed Bimini
Fixed Bimini collects additional rain
Slight forward tilt on Bimini sends water to the pilothouse roof and a filter.

Then I fill 4 tanks -

Two gravity tanks at pilothouse roof height
Black CPVC section on roof for hot (5 gallons)
Inside PVC section for cold (5 gallons)

Two existing "heavy" tanks are below the sole
Initial Overflow shunts from cold roof tank to the two hull tanks
Final Overflow sends excess water overboard from roof

The existing electric supply pump from big tanks will be replumbed to feed the small roof cold tank. A manual foot pump already exists in my setup but is disconnected at present.

How does this design impact stability, righting moment etc? Not at all because Pilothouse roof tanks are simply emptied during passage and/or rough weather.
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Old 19-02-2017, 09:29   #21
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Re: Gravity tank for fresh water - any experience?

If I remember right, Jack Wharram was writing about gravity feeded water to the galley. I think a tank under the roof is about 5 feet over the sink, the pressure will be about 0.15 bar or (rounded) 2.18 PSI. With this pressure the use of water will be less. But in the tropics the problem will be that water in a tank under the roof will be warm, and so far it needs to be more chlorinated.
As written by an other CF member I would also try to use a collabsible tank.

In short it will work but you need to have an eye to the detail.

Good luck
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Old 19-02-2017, 09:36   #22
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Re: Gravity tank for fresh water - any experience?

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I would add that a well-fitted yacht should "collect her own water and electricity".
A rain water collection system is a great addition to any cruising yacht. Although it is optimistic to expect it to supply all water in all climates.

We have a simple system on our current yacht. Before the water maker was installed we used it often. Now it serves an excellent back up if the water maker should ever fail.

It is one of the many systems we have duplicated on our new yacht.
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Old 19-02-2017, 09:45   #23
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Re: Gravity tank for fresh water - any experience?

Lynn & Larry Pardey did it on I think at least one of there boats , can't remember if it was for kerosene or water . We have two foot pumps and two tanks of water , the big one we put dock water in and the small one we put bottled water in . The foot pumps are fine until they leak or when one bites my ankle . moniia this Westsail you speak of , please elaborate . Pictures ? Thanks .
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Old 19-02-2017, 10:03   #24
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Re: Gravity tank for fresh water - any experience?

Only 5.5 gallons? I use 1/2 gallon jugs. Easy to store and easy to use. Also reduces chances of contamination less. I use my big tanks for non-essentials.
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Old 19-02-2017, 10:29   #25
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Re: Gravity tank for fresh water - any experience?

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Hello,
Call me old fashioned or even backwards ..............
OK, you are old fashioned or even backwards. Other things come to mind as well.

Yes, you can mount a tank over your sink and use gravity to supply water to the sink but how are you going to get water into the tank in the first place? Five gallons isn't going to last very long.
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Old 19-02-2017, 10:33   #26
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Re: Gravity tank for fresh water - any experience?

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[...]I have some space in which I can actually inbuilt a small tank (OK, laminate insides of this space and keep little slope) and I wondered how low could I get with it.[...]
If you are going to drink that water, laminate (be it epoxy or not) may not be the best choice for tank walls. Perhaps see how much a custom PE tank made to fit the space available would cost?
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Old 19-02-2017, 10:33   #27
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Re: Gravity tank for fresh water - any experience?

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(...) . moniia this Westsail you speak of , please elaborate . Pictures ? Thanks .

It's not really a Westsail, it is a copy of it made in ferrocement by boatyard in Weymouth in 1979, with a bit different (bigger) rig.
Lovely boat

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Old 19-02-2017, 10:35   #28
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Re: Gravity tank for fresh water - any experience?

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OK, you are old fashioned or even backwards. Other things come to mind as well.

Yes, you can mount a tank over your sink and use gravity to supply water to the sink but how are you going to get water into the tank in the first place? Five gallons isn't going to last very long.


Please, make an effort to read posts before typing yours, will you?
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Old 19-02-2017, 10:51   #29
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Re: Gravity tank for fresh water - any experience?

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If you are going to drink that water, laminate (be it epoxy or not) may not be the best choice for tank walls. Perhaps see how much a custom PE tank made to fit the space available would cost?


Custom pe would be too much hassle. And I see I need to elaborate a bit:
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Those coatings come from many different manufacturers and in many names and are approved as potable water tanks inner coating (designed mainly for steel tanks but covering epoxied surface is not a problem and creates proper barrier from anything you use for a tank.

And epoxy itself after being properly cured does not give any adverse effects anyway, but with this extra coating makes it completely safe.
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Old 19-02-2017, 11:00   #30
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Re: Gravity tank for fresh water - any experience?

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Please, make an effort to read posts before typing yours, will you?
Perhaps you could make your posts more clear in the first place and include pertinent information while leaving out irrelevant information.
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