Water tanks vs jerry cans: rethinking your off-road van's water setup

Somewhere on the Tanami last dry season I watched a bloke unbolt a cracked 95-litre poly tank from under his van, at a fuel stop with no workshop, no spare tank and three hundred kilometres to the next town with parts. He'd hit a washout at the wrong angle and the tank strap had done nothing to stop the tank flexing against a mount bolt. He finished the trip on jerry cans lashed to his roof rack. It's the kind of thing that sticks with you when your whole existence out bush depends on having water when you need it.

I run a mixed system in the Troopy now, a modest fixed tank plus jerry cans, and it took a few seasons of getting the balance wrong to land on something I trust. The question of tanks versus cans isn't really about capacity. It's about failure modes, and what happens to your trip when one part of the system lets you down a long way from a tap.

What a fixed tank actually gives you

A bolted-in poly or stainless tank is convenient, no argument. It's plumbed to a pump, it feeds your tap and shower without you lifting anything, and a well-mounted tank sits low, which helps your centre of gravity rather than hurting it. Most off-road vans run somewhere between 95 and 180 litres in a single under-floor or under-bed tank, sometimes split into two for weight distribution front to back.

The catch is that a fixed tank is a single point of failure. Crack it, split a fitting, or shear a mounting bolt on corrugations and you don't have a leak, you have a system failure. I've seen tanks fail from stone strikes on the Gibb River Road, from flex fatigue on the Anne Beadell Highway, and from a poorly bedded outlet fitting that vibrated loose over a few thousand kilometres of washboard. None of those are exotic failures. They're the normal wear pattern for a rigid vessel bolted to a chassis that's designed to flex.

Why jerry cans and bladders earn a place even with a good tank

The case for cans isn't nostalgia, it's redundancy. Twenty-litre jerry cans, whether the old steel military-pattern ones or a decent plastic equivalent, are modular. Lose one to a puncture or a bad cap and you've lost twenty litres, not your whole supply. Spread across the roof rack, the tray and inside the cab, they're also not all subject to the same failure, the same stone strike, the same corrugation flex.

Collapsible bladders (10 to 20 litre) are the softer option for filling gaps, they pack flat when empty and they're genuinely useful as a top-up reserve you keep sealed and don't touch until the fixed tank runs low. I keep two 20-litre steel jerries as an absolute reserve that never gets used for daily cooking or washing, only for the day something goes wrong. That's roughly 40 litres of water I pretend doesn't exist until I actually need it.

The numbers that actually matter

Water weighs a kilogram a litre, so this is a payload conversation as much as a plumbing one. A 130-litre fixed tank full is 130 kg sitting low and (usually) central, which is good for towing dynamics. Add four 20-litre jerries at 20 kg each and you've put another 80 kg somewhere less ideal, usually higher and further out, on a roof rack or rear tray.

That matters for two reasons. First, roof weight raises your centre of gravity and makes a Troopy or wagon feel worse on rutted tracks exactly when you need it to feel better. Second, it's payload you're spending on redundancy rather than on fuel, recovery gear or the fridge. I'd rather run a smaller fixed tank, say 95 litres, and carry my backup as cans low in the tray or behind the rear axle, than max out a single huge tank and skip the redundancy altogether.

For day-to-day usage, I budget roughly 3 to 4 litres per person per day for drinking and basic cooking, more if you're washing up properly or running a shower daily rather than every second or third day. That's a starting point, not gospel, heat and exertion change it fast. If you want the fuller sums for family rigs, our guide on water storage for family touring breaks down how that scales with more people in the van.

Where each system actually fails

Fixed tanks fail at the fittings and the mounts, not usually the tank body itself in my experience. Vibration works bolts loose, hose clamps slacken, and the outlet fitting where a rigid pipe meets a flexing chassis is the classic failure point. A tank strapped too tightly with no allowance for chassis flex will crack before one that's mounted with a bit of give in the strapping.

Jerry cans fail at the cap seal and at the seams if they're cheap plastic. Steel military-pattern cans with a rubber gasket seal are close to bombproof, I've dropped mine from tray height onto rock more than once without a leak. Cheap plastic cans crack at the handle mount or split a seam after a season of UV exposure and vibration, so if you're going to run cans as genuine backup, spend the extra on steel or a reputable heavy plastic like a Scepter or similar military-spec can.

A practical split that's worked for me

My current setup is a 95-litre fixed tank under the Troopy, plumbed to a 12V pump and a single tap, plus two 20-litre steel jerries mounted low in the rear tray as untouched reserve, plus a 10-litre collapsible bladder that lives folded flat until I actually need to carry extra for a specific leg, like the run into Bullara Station or a stretch of the Gibb River Road where bore water isn't guaranteed to be drinkable.

That gives me around 145 litres total capacity with genuine redundancy, and if the tank fails outright I've still got 40 litres of steel-can water that can't be taken out by the same failure. I'd rather have that split than 180 litres in one vessel, even though the total number looks worse on paper.

Filling, treating and not making yourself sick

Whatever you carry, treat unknown water sources properly, whether that's a rock hole, a bore or a tank at a remote station. A simple inline filter plus purification tablets or a UV steriliser covers most bases, and it's cheap insurance against a genuinely miserable week. Check current water advisories for any national park or reserve before relying on tank water there, conditions change with rainfall and algae blooms, and the relevant park authority (state parks service or the local shire) is the source to check, not last year's blog post.

One habit I've picked up the hard way: label your reserve cans clearly, "EMERGENCY ONLY," and actually stick to it. It's tempting to dip into the reserve for a quick top-up when the main tank's running low and town's still two days away. That's exactly the moment the discipline matters most.

What I'd tell someone setting up a rig from scratch

I reckon the mistake most first-time remote tourers make is treating tank capacity as the whole answer, buying the biggest single tank that'll fit and calling the water problem solved. It isn't. Capacity without redundancy just means a bigger single point of failure. If you're planning anything like the Anne Beadell Highway or a full lap of the Gunbarrel Highway, work out your daily litres, size a fixed tank for the bulk of it, and put a genuine, sealed, untouched reserve somewhere the same failure can't reach.

It's not a complicated system. It's just one that assumes something will eventually go wrong, because out there, eventually it does.