Water Tank vs Jerry Cans: Cost, Weight and Payload

Buy cans first, add a small plumbed tank later, and never buy a large tank as your first water decision. Four Scepter 5 gallon cans hold 20 gallons for $111.96 and need nothing installed. The same 20 gallons as a plumbed system, using an Ameri-Kart 20 Gallon RV Fresh Water Tank at $145.00 and a SHURFLO Revolution 4008-101-E65 RV Fresh Water Pump (3.0 GPM, 55 PSI) at $127.05 plus hose, fittings, a strainer and a fused circuit, lands at $372.05 to $422.05. The tank buys you a tap, which is genuinely worth money. What it costs you is the ability to leave the weight at home, and that is the trade almost nobody prices correctly.

A quick definition, because the terms get used loosely. A fixed tank is a rigid container mounted permanently in the vehicle and plumbed to a pump and a tap, so water arrives under pressure when you open something. Jerry cans are portable rigid containers you fill by hand, carry by hand and pour from, and they are complete systems on their own. The comparison below holds capacity constant at 20 gallons, which is where the two approaches meet on equal terms.

What does each approach actually cost and weigh?

Here it is in dollars and pounds, using real listed prices. The plumbing allowance is a budget figure rather than a product price, because hose, elbows, clamps and a tap depend entirely on your layout, and the table says so plainly.

Three rows in that table decide most builds. The dollars row says the tank costs roughly $260 to $310 more for identical capacity, which is a solar panel or most of a DC-DC charger. The dry weight row says the tank route installs 30 lb of permanent hardware against 5 lb of removable containers. And the last practical row is the one that matters most: the minimum weight you can travel with is 167 lb for the tank and 42 lb for the cans.

A word on the full weight figures, since they look closer than expected. Water is 8.34 lb per US gallon, so 20 gallons is 167 lb either way and nothing changes that. The tank route is heavier when full because the tank shell, the pump and the plumbing come along too. The cans are lighter full and dramatically lighter empty, and empty is the state that matters when you are deciding what to load.

Why is payload flexibility the strongest argument for cans?

Because it is the only dimension where the gap is not a matter of taste. Everything else on this page is a preference you could reasonably argue either way. You can leave three of five cans at home for a weekend. You cannot half-drain a plumbed tank without losing the trip.

Think about what a part-full fixed tank actually means. You could fill a 20 gallon tank to 10 gallons and save 83 lb, and you would then be carrying 83 lb of water free to move inside a container with a lot of empty space above it. Unbaffled, that mass arrives a fraction of a second after every direction change, and on a side slope or in an avoidance manoeuvre it is working against you. Baffles help and do not eliminate it. So in practice a fixed tank travels either near full or near empty, and near empty means you have brought the hardware without the water.

Read the weekend row. Two cans is 84 lb where the tank is 167 lb, so the cans hand back 83 lb of payload on the trip type most people take most often. Eighty-three pounds is a set of recovery boards, a full toolbox and a second passenger's luggage. Nothing else in the build offers that lever. You cannot fit half a battery for a short trip, a rooftop tent never gets lighter, the fridge weighs what it weighs. Water is the one heavy item whose quantity is a per-trip choice, and a fixed tank throws that choice away in exchange for a tap.

The last row is the honest counterweight. If you actually need 25 gallons, five cans at 209 lb is heavier than a 20 gallon tank, and at that point the tank is looking better on both weight and convenience. The cans argument is strongest precisely where most trips live, at one to three nights, and it weakens as trips get longer. Work out where your own trips fall using the water capacity calculator, then check the result against the vehicle in the payload weight calculator. If half your payload headroom is going into one item, you have found the decision that matters.

Which is easier to refill?

Cans, and it is not close. A can goes to the water. You carry it to a spigot, a drinking fountain, a campground tap, a gas station washroom or a friend's kitchen sink, fill it and carry it back. Nothing has to reach the vehicle.

A fixed tank needs the water to come to it, which in practice means a hose long enough to reach the fill port from wherever the tap is. That is fine at an RV park with a dedicated potable water station and awkward everywhere else. Plenty of taps are threadless, plenty of spigots sit in a concrete box, and plenty of fill ports end up on the side of the vehicle that faces away from the tap. Carrying a hose, an adapter and a funnel solves it, and that is three more items and a wet hose to stow.

There is a workaround that reveals something about the whole comparison: many tank owners refill their tank by pouring cans into it. That works, and it also means they own cans, which is the hybrid setup arriving by accident rather than by design. If you are going to own cans anyway, own them deliberately and size the tank smaller.

Which puts the weight in a better place?

The tank, clearly, and this is its strongest argument after daily convenience. You choose where a fixed tank goes exactly once, and if you choose well it goes low and inside the wheelbase, slightly ahead of the rear axle. That is the best available place for 167 lb: low keeps the centre of gravity down, and inside the wheelbase keeps the load off the lever arm behind the rear axle.

Cans go wherever they fit, and where they fit is usually less good. On the cargo floor at the back is the common answer, which is behind or near the rear axle. On a rear swing-out carrier is worse for the same reason and adds leverage. On a roof rack is worst of all: at 42 lb each, four cans is 167 lb at the highest point in the vehicle, and dynamic roof load on a standard unibody vehicle is commonly 150 to 220 lb, so four full cans have consumed the entire allowance before the rack itself. Check your own owner manual, treat the vehicle roof rating and the rack rating as two separate limits where the lower governs, and put water on the roof only if you enjoy discovering how a tall load feels on a side slope.

Cans also have to be restrained. Forty-two pounds loose in a cargo area is a projectile in a collision and a wandering weight on a corrugated road, so they get straps, a rack or a cradle, just as a battery gets a tray and hold-down . The payload and GVWR guide covers the axle limits properly, including why a vehicle can be inside its GVWR and over its rear GAWR at the same time, which is exactly what rear-mounted water does.

Which eats more cargo space?

The tank wins on packing efficiency, and by more than the raw volumes suggest. A rigid tank slides into dead space: under a bed platform, inside a bench, in the void behind a wheel arch. That space was not usable for anything you needed to reach, so the tank effectively costs nothing in accessible cargo volume.

Cans are the opposite. They are boxy, they must stay upright, and they need not just their own footprint but clearance above them so you can lift a 42 lb can out without unloading everything else first. Four cans occupy prime floor space in the part of the vehicle you reach into most often. They also do not stack well when full, and a can buried under the cooking box is a can you will resent.

One offset worth noting: cans that are empty take the same space as cans that are full, unlike a tank which is always the same size either way. So on the return leg of a long trip you are hauling four empty boxes around. Some builds solve that with a bladder for bulk and cans for daily use, though a bladder brings its own problems: you cannot see inside it, and it punctures.

What actually breaks?

A can has a body, a cap and a spout. That is the whole failure list, and the worst outcome is losing 5 gallons and buying a $27.99 replacement. Nothing about it depends on power, and nothing about it can fail while you are away from the vehicle.

A plumbed system has a longer list, and each item is a real thing that happens. The pump can lose its prime, its valves can clog with grit, its pressure switch can stick, and its internal bypass can fail so it hunts on and off. Hose clamps loosen under vibration. Push-fit fittings that were never fully seated weep. Threaded plastic fittings crack if overtightened. A fuse blows and the system is dead until you find out why. And any of those can happen while you are up a trail, which is how a build discovers whether the water is under a bed platform that has to be disassembled to reach.

The pump deserves its own paragraph because it is the one part that is also an electrical liability. A SHURFLO Revolution 4008-101-E65 RV Fresh Water Pump (3.0 GPM, 55 PSI) draws roughly 7 to 8A while it runs at 3.0 GPM and 55 PSI. That current is brief, and the wiring does not care about brevity: it heats at 8A whenever 8A is flowing. So the circuit gets its own way on a FASTSTORM 12 Way Blade Fuse Block with LED Indicators (12V) , a 15A fuse at the source of power, and 10 AWG conductor on runs up to about 20 ft to keep voltage drop inside the 0.36V target. A motor fed low voltage draws more current to do the same work, which is why a pump on undersized wire runs hot and dies early. The fuse sizing chart gives the fuse for every conductor size. There is also a failure mode worth naming: a pump that cannot hold pressure runs continuously, and a system that normally costs under 2 amp-hours a day can quietly consume 20 overnight.

Cans have none of that, and the honest counterweight is that they also give you none of the convenience the complexity was buying. Simplicity is not free, it is just paid for differently.

Which handles freezing and sanitation better?

Cans, on both counts. On freezing, a full tank is what splits when it freezes: water expands as it turns to ice inside a closed container and the container gives way, so you lose a tank wall, a pump head or a plastic fitting, and you find out when it thaws into your build. Cans fail one at a time, cost $27.99 to replace, and can be carried into a heated space overnight so you still have liquid water while the plumbed system is drained for the cold. Draining a tank system properly means every tap, the low point, the lines and the pump head, and the pump head is the part people forget.

On sanitation, the deciding factor is access. Biofilm is the layer of microorganisms that forms on any wet surface left standing, and a warm plastic container of still water in a vehicle is close to ideal for it. A can has a wide mouth: you can see inside, get a brush in, scrub it and know whether the job worked. A sealed tank with two threaded ports gives you chemistry and hope. If you do buy a tank, weight the availability of a real inspection port heavily, because a tank you can get a hand inside is a tank you can actually recover.

There is a smaller point in the cans' favour that turns out to matter. Cans are independent, so contamination or a bad fill affects one fifth of your water rather than all of it. That also makes them the natural way to separate drinking water from washing water, which is the practical filtration strategy in a vehicle: keep the water you drink in a container you trust, and fill the bulk supply less fussily. On filtration generally, remember that a carbon filter improves taste and is not a pathogen barrier, and that questionable source water needs a rated purifier or boiling. The overland water system guide works through filtration, sanitising and freeze protection in detail.

What is the hybrid setup, and why do experienced builds end up there?

Because it beats both. The layout most builds converge on after a season or two is a modest fixed tank of 10 to 20 gallons feeding the sink and pump, plus one or two 5 gallon cans carried only when the trip needs the range.

Look at what that solves. The tank gives you a tap for the ninety percent of water use that is washing hands, rinsing a plate and filling a kettle, which is the thing cans are genuinely bad at. Sizing the tank at 10 to 15 gallons instead of 30 keeps its permanent weight at 83 to 125 lb rather than 250, so the always-there penalty is manageable. The cans then carry the variable part of the requirement, so the payload decision stays yours on the morning you leave. And the cans are a complete independent backup: when the pump fails at a trailhead, you still have water, which a single-tank build does not.

Priced out, a 20 gallon tank plumbed with a pump plus two cans is roughly $372.05 to $422.05 plus $55.98, so around $430 to $480 for 30 gallons of total capacity with 10 of it optional. That is more than either approach alone, and it is the only configuration that has no obvious weakness. The intermediate overland power setup is the tier where this usually gets built, because it is the point at which a vehicle has a fused distribution block and a battery bank that can carry a pump circuit without anyone thinking about it.

Which should you buy?

Buy cans if you are early in a build, if most of your trips are one to three nights, if your payload headroom is tight, if you travel in freezing weather, if you want zero added electrical load, or if you would rather spend $260 on a solar panel than on plumbing. Cans are also the right answer for anyone using a vehicle that has to go back to being an ordinary vehicle on weekdays, because they lift out.

Buy a plumbed tank if your trips routinely run four nights or longer, if you live in the vehicle for weeks at a time, if you want a working sink and an outdoor shower, if you have a bed platform or bench with genuine dead space under it, and if you have the payload headroom to carry 167 lb on every trip including the overnight ones. It is a comfort purchase, and comfort is a legitimate thing to buy.

Do not buy a large tank as your first water decision. A 30 or 40 gallon tank at 250 to 334 lb is the single most common way a build ends up over its rear axle rating, and almost nobody who fits one uses that capacity regularly. Start with cans, learn what you actually consume over a season using the water capacity calculator as a check against your own habits, and then fit the smallest tank that covers your real pattern. Capacity you do not use is weight you carry on every trip forever.

Weight limits, roof load ratings and road legality vary by vehicle, model year and jurisdiction. Payload, GVWR and GAWR figures must be read off your own door jamb sticker rather than a brochure, and aftermarket rack or carrier ratings are separate limits where the lower one always governs. Everything on this page is researched guidance based on published manufacturer specifications and verified owner reviews, not an engineering sign-off, not a legal opinion and not a substitute for the installation instructions supplied with your tank, pump or carrier. On water safety, nothing here is medical advice: a carbon filter improves taste and is not a pathogen barrier, questionable source water needs a purifier carrying a published rating or boiling, and cartridge replacement intervals come from the manufacturer.

Where to go next

• Overland water system guide, for plumbing, filtration, sanitising and freeze protection.
• Water capacity calculator, for your own gallons, days and reserve.
• Payload and GVWR guide, for the axle limits water pushes against.
• Payload weight calculator, to check the whole build against the sticker.
• Fuse sizing chart, for the pump circuit fuse.
• Intermediate overland power setup, the tier where a plumbed pump circuit belongs.