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Old 24-11-2020, 19:12   #1
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Vertical flexible freshwater tank?

My freshwater tank is down inside my keel (it's a compartment in the keel, really, it's not removable). It was in pretty rough shape, and I've cleaned it up a lot, but I still don't want to put my freshwater in it. I am thinking that I can put a flexible bag down inside it. But, all the flexible tanks I've found are flat pancakes (or triangles for the bow), and the fittings aren't in the right place for me. Does anyone know of a company that makes vertical flexible bag tanks? Where the in valve would be at the top and the out would be near the bottom when vertical?

I attached a picture of the current "tank"; I just coated it in epoxy paint to stop the rust from coming back. It's a weird shape and two to three times as deep as it is wide or long, which is why I thought the bag might be an easier idea than trying to find a vertical rigid tank and dropping it in. The "in" is on the forward end, which in this picture is the bottom, and the "out" is on the aft end, which is at the top of the picture (I will probably need to cut off that metal extension no matter what I do). Any recommendations?
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Old 24-11-2020, 19:29   #2
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Re: Vertical flexible freshwater tank?

The compartment you show is not functional as a tank? It appears that installing a top would complete it. Assuming that you have a steel boat (based on your comment about rust) it is common practice to have tankage for diesel and water built into the hull structure. Large water tanks for potable water (up to city sized) are commonly made from steel. Properly painted they have a very long life.

From the pix it looks like you have a flange surrounding the tank with holes in it? I'd assume that this exists to bolt down a top cover plate? If so, you can make the top plate out of plexiglass which will enable you to inspect the tank interior at a glance, which is a nice feature.

I would suggest that you topcoat your paint job with an epoxy paint specifically made for potable water tanks. These paints are formulated to not emit contaminants into the water. PPG is one source for these.
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Old 24-11-2020, 19:35   #3
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Re: Vertical flexible freshwater tank?

Quote:
Originally Posted by Pauls View Post
The compartment you show is not functional as a tank? It appears that installing a top would complete it. Assuming that you have a steel boat (based on your comment about rust) it is common practice to have tankage for diesel and water built into the hull structure. Large water tanks for potable water (up to city sized) are commonly made from steel. Properly painted they have a very long life.

From the pix it looks like you have a flange surrounding the tank with holes in it? I'd assume that this exists to bolt down a top cover plate? If so, you can make the top plate out of plexiglass which will enable you to inspect the tank interior at a glance, which is a nice feature.

I would suggest that you topcoat your paint job with an epoxy paint specifically made for potable water tanks. These paints are formulated to not emit contaminants into the water. PPG is one source for these.
Yea it is a steel boat and therefore a steel tank, and the epoxy paint I've put on it at the moment is PPG's Amercoat 235, which I had on hand because I've been using it elsewhere. I also have the top plate, it looks like it's aluminum. The trick is that I'm worried that it won't ultimately hold the paint that well, even if I use the special potable water paint as a topcoat, because it was really really bad before I treated and painted it. This is what it looked like post-rust treatment but pre-paint (I couldn't get the rest of that old paint off, either, so I'm banking on the fact that the Amercoat will hold it all in)
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Old 24-11-2020, 20:00   #4
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Re: Vertical flexible freshwater tank?

Yeah, that doesn't look good. I wouldn't trust it to hold up long term either.

If you can't find the tank you're looking for you might consider laying up a few layers of fiberglass inside your tank. In effect you will be making a new fiberglass tank which is custom fit to your existing one. You'll need to run the fiberglass up over the top of your flange and will need to drill it for your cover mounting holes, which could be a pain.
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Old 24-11-2020, 20:06   #5
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Re: Vertical flexible freshwater tank?

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Originally Posted by Pauls View Post
Yeah, that doesn't look good. I wouldn't trust it to hold up long term either.

If you can't find the tank you're looking for you might consider laying up a few layers of fiberglass inside your tank. In effect you will be making a new fiberglass tank which is custom fit to your existing one. You'll need to run the fiberglass up over the top of your flange and will need to drill it for your cover mounting holes, which could be a pain.
Ha yea it does not. I think it will hold up decently well and I'd trust it to put other things in, just not freshwater.
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Old 24-11-2020, 22:20   #6
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Re: Vertical flexible freshwater tank?

Couple of points:

There are firms who make custom welded plastic tanks to whatever dimensions you wish, with fittings wherever you wish. Typically they are not more expensive than custom bladder tanks and will last FAR longer. We had various misadventures with bladders and don't recommend them for permanent installation.

Secondly, to be direct, having a bit of rust in a potable water tank isn't gonna cause you any health issues. Heaps of houses with rusty steel water pipes in the ...

Good luck...

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Old 25-11-2020, 06:58   #7
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Re: Vertical flexible freshwater tank?

Quote:
Originally Posted by Pauls View Post
... I would suggest that you topcoat your paint job with an epoxy paint specifically made for potable water tanks. These paints are formulated to not emit contaminants into the water. PPG is one source for these.
Indeed!
Amercoat 235, multi-purpose epoxy has a very limited* food rating:
Canada Health and Welfare, dry food, fish holds (off white and buff only)
USDA approval for incidental food contact (limited colors)

https://www.cgedwards.com/ameron/amercoat235.html
http://www.vailsfiberglass.com/wp-co...en-US_P052.pdf
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Old 25-11-2020, 07:06   #8
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Re: Vertical flexible freshwater tank?

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Originally Posted by Jim Cate View Post
There are firms who make custom welded plastic tanks to whatever dimensions you wish, with fittings wherever you wish. Typically they are not more expensive than custom bladder tanks and will last FAR longer. We had various misadventures with bladders and don't recommend them for permanent installation.

Jim
This is my other option, but the trick is there will inevitably be space between the plastic tank and the outer metal tank, so I'll have to construct some sort of platform and cushioning to prevent chafe, and also some way to get water out of the bottom without removing the inner tank, as it will inevitably get in there. Which is why I thought the flexible might be easier because it would be easier to remove and I wouldn't need to build a whole platform (but maybe still get some cushioning)
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Old 25-11-2020, 09:52   #9
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Re: Vertical flexible freshwater tank?

Jim, I am also in need of additional water tankage which would have to be custom sized. Can you share the names of the companies you mentioned?
Thanks, Ken
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Old 25-11-2020, 10:00   #10
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Re: Vertical flexible freshwater tank?

a) Have 1 or 2 plastic tanks made that you can put in there.
b) or Buy a flexible tank, they have been common with fittings on the top in the past, must be available now.
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Old 25-11-2020, 10:36   #11
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Re: Vertical flexible freshwater tank?

Ronco Plastics makes quality polyethylene water tanks, in many (500+) shapes & sizes, with fittings installed to your specification.
Check them out. You might get lucky, and find your perfect fit.
https://ronco-plastics.com/product/w...-holding-tank/

https://ronco-plastics.com/wp-conten...m-2_081018.pdf

https://ronco-plastics.com/wp-conten...d-7.3.2020.pdf
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Old 25-11-2020, 11:44   #12
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Re: Vertical flexible freshwater tank?

I've built and repaired a lot of water tanks. Whatever they're made of, I coat the tank with a potable approved coating. The coating and the tank lasts the life of the boat.
The epoxy will probably stick if the surface was decently prepared. All the coatings I've used stick fine to epoxy. They also stick fine to aluminum, fiberglass, slightly rusted mild steel. and stainless. The coating applied to proper thickness doesn't wear away. Chlorine and other biocides don't seem to hurt it.
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Old 25-11-2020, 12:46   #13
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Re: Vertical flexible freshwater tank?

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Originally Posted by freelandken View Post
Jim, I am also in need of additional water tankage which would have to be custom sized. Can you share the names of the companies you mentioned?
Thanks, Ken
Ken, I've not had any custom plastic tanks made, only aluminium and s/s, so no personal experience. However, Googling "custom plastic tanks" brought up a number of firms that can build them. I suspect that you can find one in your area.

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Old 25-11-2020, 16:10   #14
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Re: Vertical flexible freshwater tank?

If for some reason you can't get an off the shelf or custom 'plastic' tank, you could make your own out of either plywood or fibreglass. Coat the inside with a suitably rated epoxy for potable water.

The space doesn't look too tricky for a custom tank of any material.
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Old 26-11-2020, 04:25   #15
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Re: Vertical flexible freshwater tank?

Here in aust a company called turtle pac have been making flex tanks to mill spec for many years custom shapes no probs I think they have a US contact ,turtle pac @yahoo.com .should find them .good luck .⛵️⚓️
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