Building Watertanks

[Uncle Bob]

Originally Posted by coopec43

I'm sure I read on a thread some time ago that only about a third of boaties claimed they drank boat tank water (they drank bottled water instead). I'm not surprised as a lot (most) tanks cannot be cleaned because they don't have large inspection hatches to enable them to be regularly cleaned.

This article would seem to confirm that most people drink bottled water. (Sadly most empty plastic bottles would be heaved overboard).

https://www.yachtingworld.com/featur...c-survey-66549

I'll treat the installation of a water-maker as top priority.

Have to agree with this, in my case the tank is essentially inaccessible, had a smell when I bought it and even though repeated cleaning with bleach and flushing has gotten rid of the smell I am still reluctant to drink from it, although I have and there is no taste I tend to use the 10 litre plastic containers and refill from town water.

[AKA-None]

I’d add baffled if I were building a tank

[Pete7]

Originally Posted by coopec43

I'm sure I read on a thread some time ago that only about a third of boaties claimed they drank boat tank water (they drank bottled water instead). I'm not surprised as a lot (most) tanks cannot be cleaned because they don't have large inspection hatches to enable them to be regularly cleaned.

I think might depend were you are sailing. Generally Europe has excellent water quality, often free and state monitored, I have always drunk from the boats tanks. Therefore very few water makers on yachts staying in Europe though a few in the Med.

However, our tank is bleached each year, in fact just done it for the coming season. We also installed a large clear inspection hatch so we can see what is going on.

That said, I can see the problem if your "off piste" and the local water is in short supply or of dubious quality.

[capn_billl]

Originally Posted by Chotu

This nut is too big to crack. I was trying to do the same thing. It's just not worth the time, money and health risks involved.

Get a polyethylene water tank and make it fit. You'll be very happy you did.

Polyethylene is a thermal plastic that is heat deformable, and weldable.

If it was MY boat, I would buy a couple sheets of it, and weld it into place.

Polyethylene is durable, you can buy food grade, UV stabilized, any color.

I've made welded pressure tanks rated to 100psi.

No coatings, or curing needed.

[skenn_ie]

Originally Posted by chowdan

Hey all,


I am planning to build the tank out of 1/4" marine ply, nailing it all together with a nailgun, then epoxying the entire interior/exterior with some 6oz cloth - probably 2-3 layers. All joints will have tapes seams with biaxial cloth. I'll put in a few baffles as well.
:\

I suspect that 2-3 layers won't be enough to make it waterproof unless you add a thick layer of epoxy afterwards. My superstructure is a foam sandwich, and 3 layers was still porous. Admittedly, I was building in the same manner as I did with an aircraft, applying just enough resin to bind the fibres without adding unnecessary weight. An extra coat of resin was needed, then topcoat.

[Jef & Marin, Netherlands]

You might consider building your own polyethylene or polypropylene water tank. Buy the flat sheet, weld it with one of those Chinese welding tools which cost 200$.

There are 2 types of welding: by adding molten material, or hot-air melting; I would go for the first. Some tools can do both.

There are enough how-to videos on Youtube. Polypropylene is best for diesel fuel, polyethylene is good enough for water. To fill and get water out you can weld-on a same-material pipe; or use through-hulls with rubber rings; glue does not work well on polyethylene.
If it has to follow the shape of the hull you will need to bend that side with heat or build-up from separate sections.

Disadvantage of this is extra weight and volume lost by the double wall.
Advantages: No danger of poisoning yourself, of bad taste and of difficult chemicals.
Of course there are companies which would be prepared to do this job for you.

I have never done this, however I will surely do this when necessary.
It is i.m.o. much simpler and less work than making 2 holding tanks from honeycomb and glass fiber/epoxy which I did a few years ago.

[skenn_ie]

Originally Posted by Jef & Marin, Netherlands

You might consider building your own polyethylene or polypropylene water tank. Buy the flat sheet, weld it with one of those Chinese welding tools which cost 200$.

.

Some plastic materials have woven firbeglass partially embedded in one side. Cut, weld, then apply more fibreglass to the outside for reinforcement, particularly the seams.

[jsanton]

Didn’t read entire thread so forgive me if someone else has suggested this. How about building it with starboard and a plastic welder?

[StoneCrab]

I guess you work with the material that you know but I would build the tank from metal.

The fabrication costs wouldn't be that high even if you used stainless.

Make a cardboard mockup. Test fit it. Then bring the pattern to a sheet metal shop. They can do the straight cuts with a shear, plasma cut the curves and TIG weld the joints before you mix up the epoxy.

If the tank is well supported, it doesn't have to be thick.

[skenn_ie]

Originally Posted by StoneCrab

I guess you work with the material that you know but I would build the tank from metal.

The fabrication costs wouldn't be that high even if you used stainless.

Make a cardboard mockup. Test fit it. Then bring the pattern to a sheet metal shop. They can do the straight cuts with a shear, plasma cut the curves and TIG weld the joints before you mix up the epoxy.

If the tank is well supported, it doesn't have to be thick.

It may not be relevant, depending on mileage ang desired longevity but :



Sharp corners tend to fracture. Stainless work hardens, and age hardens. Sharp corners focus stresses. If you can find a GOOD fabricator, they will be able to fabricate with radiused corners, with the welded seams on the flat rather than the corners.

[MVDarlin]

Don't mess with coatings. Just buy a bladder. I converted a deck box into an extra tank. 100 gal with a bladder. Easy. Less than $200

[MVDarlin]

Also. Re quality. Buy a Zero Water filter pitcher for coffee and drinking water. It will produce water that tests at 5ppm or less for months. Just fill a few bottles from time to time and have a spare filter on board. Works great and comes with a tester.

[coopec43]

Originally Posted by StoneCrab

. Then bring the pattern to a sheet metal shop. They can do the straight cuts with a shear, plasma cut the curves and TIG weld the joints before you mix up the epoxy.

What has epoxy to do with stainless steel? (I'm intrigued!)

As other person(s) have said SS work hardens with time

[robwilk37]

went down this road a couple years ago on my build. right before my head exploded i found ronco plastics in so cal. tons of semi-custom shapes made to order. well worth finding one thats close to your dimensions, pull the trigger and go sailing...

https://ronco-plastics.com/product/w...-holding-tank/

my .02