Any sheeties here?

[V8Ian]

Particularly with stainless experience?
I need a drinking water tank, 2200mm x 500mm x 800mm high. There will be two baffles across the 2200 width.

My questions are:
1) what grade stainless should I use?
2) what thickness material would be required?

Bear in mind it will have to withstand road travel at highway speeds.
TIA

[bee utey]

Other questions to ask yourself:

1. How is it to be supported, welded on brackets or a cradle.

2. How is it to be protected against stone impact, thicker sheet or other protection like glued on rubber sheeting.

As an engineer I would also consider adding at least one extra floor stiffener every 200-300mm or so, as a flexing floor will crack welds. I've repaired plenty of mild steel fuel tanks with poorly designed mounts but haven't yet gone near SS.

[V8Ian]

Hi Jilden, it will be mounted, insulated by rubber, in the luggage compartment beneath my coach, stone impact won't be an issue. It will be secured to 100x100 well braced RHS from which the floor of the luggage compartment is suspended 850mm below the chassis.

[bee utey]

Well then the big issue is the flexing of large flat areas. Your chosen fabricator will be the best judge of thickness versus folded in stiffening ribs. Stainless being expensive there's a case to be made to make lighter material do the job of heavier but flat material. Also maximum sheet sizes will determine how well placed long welds are, I'd imagine that 2400 by 1200mm might be the largest sheets you can buy. You might be better off with two 1100mm long tanks linked by taps, allowing you to use two sheets cross wise. End sheets should be arranged with a small lip facing inwards or outwards so they are easier to weld in and don't fracture as quickly.

[V8Ian]

The grey and black tanks, I'll fab from aluminum but for drinking water I want a food grade stainless.

[Saitch]

Two tanks would be a good back up option too.

[Pub247]

I'm a metal worker, bee utey has sound advice

304 will be fine for water. It is a very large tank. sheet limitation will be an issue, it would be easier and cheaper to make 2 tanks 1100 long as a sheet of 2400x1200 would work better for less welding and more folding. Having lips folded on edges or end plates adds strength as will help welds from cracking

Personally i would use 2mm thick you might get away with thinner 1.6mm. I Would also suggest it to be purged welded or at least sent of to be electro-chemically passivated.

[PhilipA]

When it became fashionable to have stainless tanks on Camper trailers, I met several owners who had lost all their water because of flexing of the stainless causing it to work harden then crack along the baffle lines.

Meanwhile my $85 plastic tank soldiered on for about 15 years until some gravel caught in the stone shield wore it through.

I reckon that plastic is a better option, unless you are particularly affronted by taste, which I find hard to notice.
Don't nearly all caravan manufacturers use plastic?

Regards Philip A

[trout1105]

When it became fashionable to have stainless tanks on Camper trailers, I met several owners who had lost all their water because of flexing of the stainless causing it to work harden then crack along the baffle lines.

Meanwhile my $85 plastic tank soldiered on for about 15 years until some gravel caught in the stone shield wore it through.

I reckon that plastic is a better option, unless you are particularly affronted by taste, which I find hard to notice.
Don't nearly all caravan manufacturers use plastic?

Regards Philip A

+1 for plastic tanks, they are pretty much bullet proof that's why most cars these days have plastic fuel tanks.

[Pedro_The_Swift]

just to twist that knife,,, [bigwhistle]
400L


https://proxy.duckduckgo.com/iu/?u=https%3A%2F%2Ftse1.mm.bing.net%2Fth%3Fid%3DOIP. gtPmGg0UXYA8l-urLKinlgHaEn%26pid%3D15.1&f=1

[Blknight.aus]

Id recommend plastic as well.

I also strongly reccomend 2 tanks that are not joined in a manner that will permit syphoning. You might find that even in plastic 2 tanks are cheaper than one large tank. Espescially when it comes to custom fabricated ones.

[V8Ian]

I have considered plastic, but custom made saves space and minimises liquid movement, also with plastic, being flexible, how do I secure it?
After the holidays I will enquire what Fusion Australia: The Best in Plastic Piping System Products & Fabrication (https://fusionaus.com) can offer.

[V8Ian]

Dave, custom SS tanks will only cost me the price of materials. [bigwhistle]

[cuppabillytea]

You might also consider HMDPE as an option, it doesn't react with water and is very strong and flexible.

[V8Ian]

That sounds expensive, Billy, but I could rope it in. [bigwhistle]

[LRT]

What do you do about decontamination after welding to make it potable? A certain pickling agent?

[Blknight.aus]

Dave, custom SS tanks will only cost me the price of materials. [bigwhistle]

In that case go 2 seperate ta ks designed well it will aslo save on the cost for baffelling amd help with weihht distribution on top of giving you a redundant supply.

[cuppabillytea]

That sounds expensive, Billy, but I could rope it in. [bigwhistle]
Message received and understood. No excuses I'll crack on with that.

[jerryd]

I have considered plastic, but custom made saves space and minimises liquid movement, also with plastic, being flexible, how do I secure it?
After the holidays I will enquire what Fusion Australia: The Best in Plastic Piping System Products & Fabrication (https://fusionaus.com) can offer.

I had a plastic ''made to measure'' tank done by a chap at Burpengary, cost about $100 if I remember correctly. Fits nicely between chassis rails. Can't fault it Ian [smilebigeye]

[DiscoMick]

The plastic tank in our Aussieswag camper is 16 years old and has never given the slightest problem.

[DiscoMick]

Any of these useful?
Water Tanks & Accessories Kits - AECAA Pty Ltd T/A Automotive Electrical & 4WD Acce (http://www.dolium.com.au/retail_catalogue/cat/Water_Tanks___Accessories.html#catid=Water_Tanks__ _Accessories&carea=620&csortfield=&csortfielddir=asc&crpp=10&cpag=1.09883934899485969&sqry=&sarea=&ssortfield=&ssortfielddir=&srpp=&spag=)

[DiscoMick]

Oh, is that the same link listed previously? Sorry.

[NavyDiver]

Steel tank in my camper trailer had a stone guard but still took a hit to many[bighmmm] The replacement food grade plastic 120 litre is tougher than the metal I think. No funny tastes post a flush or two. Hit mine with a hammer and it will be fine. Hit my first one and the dent might would be there for ever.

Food Grade Plastic, What is It, How is it Different from other Plastic (http://gwcontainers.com/food-grade-plastic-what-is-it/)

[Pub247]

What do you do about decontamination after welding to make it potable? A certain pickling agent?
ideally you would purge weld it and send it off to be electro-chemically passivated/polished. This will restore the chromium oxide layer which is what provides the corrosion protection.