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Old 05-09-2019, 23:49   #1
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Partition water tanks?

Hi all,

I am well into installing my new water tanks. 400 litres (100 gallons) each, port and starboard. They are being built out of plywood so I have plenty of control over the design.

Now I was going to make each side an independent single tank with the usual number of baffles, but as I was working away today I got to thinking whether I should divide each tank fore and aft so that I have four tanks, each of 100 litres, or maybe 150/50 or some other split.

All that would be required to do so is to make the one baffle of each tank a partition with no limber holes.

I accept that there would be a slight increase in complexity with the duplication of the filler, pickup and breather for each tank, but I wondered if there might be advantages. For instance, I could make one sub-tank my staging tank for the watermaker, reducing the risk of polluting my drinking water. I could also fine-tune my fore and aft trim to some degree. (Pretty minor I suppose.)

Thoughts on this?

Matt
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Old 06-09-2019, 00:02   #2
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Re: Partition water tanks?

What happened to the water tank in the keel? Why use plywood for your water tanks? It’s not hard to get a sheet of glass wax it up and lay up some fiberglass on it then fiberglass tape the fiberglass panels together?
I like the idea of a seperate tank for the water maker water. I am not sure fore and aft trim is a big issue for a Swanson 42.
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Old 06-09-2019, 00:03   #3
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Re: Partition water tanks?

What happened to the water tank in the keel? Why use plywood for your water tanks? Itís not hard to get a sheet of glass wax it up and lay up some fiberglass on it then fiberglass tape the fiberglass panels together?
I like the idea of a seperate tank for the water maker water. I am not sure fore and aft trim is a big issue for a Swanson 42.
Cheers
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Old 06-09-2019, 00:31   #4
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Re: Partition water tanks?

Quote:
Originally Posted by Fore and Aft View Post
What happened to the water tank in the keel? Why use plywood for your water tanks? Itís not hard to get a sheet of glass wax it up and lay up some fiberglass on it then fiberglass tape the fiberglass panels together?

I like the idea of a seperate tank for the water maker water. I am not sure fore and aft trim is a big issue for a Swanson 42.

Cheers


The tank in the keel is for diesel. The current arrangement of diesel on the starboard side and water on the port side is a PITA. Either you burn fuel at the same rate that you drink the water or you end up with a list to port or starboard.

I did make the day tank the way you suggested, using premade fibreglass panels, and it worked well. But I ruled it out for this job for two reasons; itís actually more labour intensive (I felt) and the length of the tanks (2200 mm) made me worry about rigidity.

The way I am constructing these tanks means they will double as boat furniture with no weight overhead.

But yeah, fore and aft trim probably wonít be all that much affected.
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Old 06-09-2019, 02:03   #5
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Re: Partition water tanks?

Let the water flow. It will make slosh sounds, but basically it's there to be used, not retained, and it should be "easy" for the water to be used.

Ann
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Old 06-09-2019, 03:23   #6
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Re: Partition water tanks?

I agree 2200 is a fair length and it would be hard to get panel stiffness without going to a lot of effort. You could always split a 50mm PVC pipe and glass that to the panel?
I still like solid fibreglass panels for baffles, mainly because itís hard to properly seal plywood edges wherever you drill limber holes.
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Old 06-09-2019, 04:33   #7
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Re: Partition water tanks?

Quote:
Originally Posted by Fore and Aft View Post
I still like solid fibreglass panels for baffles, mainly because itís hard to properly seal plywood edges wherever you drill limber holes.

Cheers


Good point. Iíve been worried about that bit.
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Old 06-09-2019, 04:38   #8
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Re: Partition water tanks?

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Let the water flow. It will make slosh sounds, but basically it's there to be used, not retained, and it should be "easy" for the water to be used.

Ann


How very hippie.

I suspect it will make a slosh sound no matter what size I choose. I wonít miss the regular ďgloing!Ē sounds from the old stainless tanks, thatís for sure.
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Old 06-09-2019, 05:23   #9
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Re: Partition water tanks?

If you do choose to make separate tanks, a tube from the bottom of each into the bottom of the next, or better yet into a manifold, with a ball valve below each tank, would let you isolate or combine at will, and save having multiple exits -just put one pickup at the end of the manifold.

Anne's "slosh" suggestion is valuable - tiny stuff doesn't accumulate in stirred water. The effect on your weight distribution is not measurable at 8 pounds per gallon moving a foot or so.

The cheap easy way to prevent slosh in a tank, if that is a goal, is "baffle balls." They are like big plastic wiffle balls, 15" in diameter, filling 2/3 of the tank. I have them in my 300 gallon fuel tanks, which started life as agricultural diesel storage tanks and have no baffles. They take up 1% of the tank space.
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Old 06-09-2019, 18:00   #10
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Re: Partition water tanks?

Iím going to run the pickups for the tanks through the tops of the tanks. Doing this for a few reasons; easier to avoid leaks as all the plumbing will be above the level of the tanks, easier to run the pipes up high where I can get to them, not in the bilge, and because the tanks also form the interior furniture of the boat, itís hard to find outlet positions down low that wonít intrude into the living space.

The water pump is self priming, so thatís no problem, but it does rule out self levelling between tanks using a manifold. But Iím ok with that.

I am starting to think maybe a 150/50 litre split on each tank, with one of the 50 litre tanks being the staging area for the watermaker and the other being the staging area for rain water collection.
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Old 07-09-2019, 04:43   #11
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Re: Partition water tanks?

Hi Matt,

We have 2 X 500l ss tanks and I wish we had 4x250. It does make plumbing a little more complex, but I believe that you no longer have all eggs in 1 (or 2) baskets. As it currently is, we can compromise our entire water supply very easily.

If you do split, make sure the manifold (with clearly labeled valves) is in an accessible place, perhaps even lockable. I don't want anyone unfamiliar playing with the system.

A staging tank for the RO output is almost a must, and with a manifold can be emptied or transfered quite easily if necessary.

One suggestion is a sight glass (vertical clear reinforced hose) on one end for quick visual confirmation of water levels.

I have installed a double filter system from Bunnings with a 10 micron primary, and a 5 micron charcoal filter supplying a seperate water tap in the galley. The charcoal filter changes the taste entirely, and will filter most nasties (except pathogens of course).

Just my 2c

Tim
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Old 07-09-2019, 14:32   #12
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Re: Partition water tanks?

Tim, thatís a lot more than two cents worth, thank you.

So, in my situation would you split each tank 50:50 (or four tanks of 200 litres each) or would you go something like 75:25 (two fifty litre tanks and two 350 litre tanks)?

I like the Bunnings filter idea on the drinking water, do you remember the brand or application? Is it a product they sell for mains water or tank water?

I am tossing up some options for tank level checking. I had the sight glass tube on the original tank, and it was ok, if a little inconveniently located. I am hoping to avoid any fittings at the bottom of the tanks, which would rule out that option, but if I give up and fit one, thatís the approach I will take. Right now I am looking at some simple DIY electronic sensors based on an electronics module I will have on board in abundance. Not my usual approach for something like this but it may be practical and reliable.

Thanks again, and point noted about the manifold.
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Old 07-09-2019, 15:52   #13
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Re: Partition water tanks?

I realise this a partition question thread but since you mention level checking and you are making the tanks from scratch, can you incorporate provision for dip sticks?
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Old 07-09-2019, 16:06   #14
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Re: Partition water tanks?

This one here:

https://www.bunnings.com.au/stefani-...ilter_p5090104

I can't remember if you have a watermaker. I guess I'd size a partition to match the typical run you'd make of your watermaker e.g. 10l/hr x 6hrs etc. The main influence for me would be futureproofing & ease of build/maintenance. Our pickups are all top mounted. Don't forget a sizable inspection port. Ours don't, so I have bought a IP67? remote wifi inspection camera (off eBay about $70) to inspect them. It is actually really handy for going in inaccessible areas before removing head lining, under floors, behind cabinets etc. I will eventually have to create an large opening for flushing etc.

If you can get an Arduino or a Raspberry module to get sensible readings from ultrasonic sensors, I'd be very interested in installing. My tanks have the nipple welded in with a stainless shutoff valve before the sight hose, so you can isolate the sight hose in case of fracture. You have to remember to open the valve to get an accurate reading. In haste, this can be forgotten, don't ask how I know ;-)

Cheers,

Tim
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Old 07-09-2019, 16:17   #15
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Re: Partition water tanks?

My two tanks have inlets in the top of the tanks for water from my watermaker,
I have a valve that only goes to one tank at a time, So I cant get both tanks contaminated with bad water,
The water coming from the tanks also goes through a valve that only uses one tank at a time,
After the valve, I have a filter then it goes to the pump which supplys all cold water every where,
Hot water comes off the cold water line and thru its own pump, Then thru its own lines every where i need hot water,
My tanks are only 70 gallons each so I dont have the weight distribution you may have,
You could put a valve in so you can distribute your tank water from tank to tank, If needed,

A single baffle in the middle of your tanks with a small hole top and bottom will eliminate all the sloshing sounds, 25mm Hole top and bottom of the baffle plate,
The baffle plate will give structural integrity to the top of the tank if you want to sit or stand on them,
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