September 10, 2026 Colby Hill

On-Board Water for Overlanding: Tanks, Jugs, and Filtration

Twenty gallons of water weighs roughly 170 pounds. People will agonize over the weight of an aluminum bumper versus a steel one, a difference of maybe sixty pounds, and then bolt a full-size water tank behind the rear axle without a second thought. It is the heaviest single consumable most builds carry, and it is the one most often mounted in the worst possible place.

Water is also the thing that ends trips. You can eat badly for a week and be fine. Run out of water on day three of a five-day trip and you are driving out whether you wanted to or not. So it is worth thinking about properly: how much, in what, mounted where, and how you keep it drinkable.

How much water you actually need

The planning number most people land on is one gallon per person per day for drinking and cooking. That is a reasonable floor, not a comfortable amount. It covers drinking, coffee, and rehydrating food. It does not cover washing dishes, rinsing hands, cleaning a wound, or the shower you will badly want on day four.

A more honest framework:

1 gallon per person per day for drinking and cooking. Non-negotiable.
Another half gallon per person per day if you want to wash dishes properly and stay clean.
Plus a reserve — one full day’s total, minimum, that you do not count in your planning. This is the water that gets you out when a trip runs long.
Plus dog water if a dog is coming. A medium dog in heat drinks more than you expect.

Heat changes all of it. Desert travel in summer can double the drinking number, and it is the situation where running short is genuinely dangerous rather than merely inconvenient. If your trips are hot and remote, plan the higher figure and accept the weight.

Two people on a long weekend land around 8 to 12 gallons with reserve. Two people for a week is 25 to 35. That is the difference between a couple of jugs and a plumbed tank, and it is the real decision driver.

Jugs versus a plumbed tank

The case for jugs

Separate containers, usually 5 to 7 gallons each, that you lift in and out.

The advantages are real and often underrated. You can carry exactly as much as the trip needs and leave the rest at home, which is the only way to avoid hauling 170 pounds on a weekend trip. You can refill them at a spigot without moving the vehicle. If one gets contaminated you have lost a fraction of your supply, not all of it. And nothing is plumbed, so nothing can leak into your build.

The disadvantages: they take up cargo space rather than dead space, they slosh and shift unless secured properly, and pouring from a 7-gallon jug is awkward enough that people end up using more water than they need to.

The case for a tank

A fixed tank, usually mounted under the bed, in a drawer system, or behind a panel, plumbed to a pump and a tap.

The advantage is convenience and packaging. A tank goes in dead space you were not using, and a tap with a foot or switch pump means you use dramatically less water because you can run a trickle instead of pouring. That efficiency is not trivial — plumbed setups routinely stretch the same gallons noticeably further.

The disadvantages: you are carrying the full weight whether the trip needs it or not, unless you make a habit of filling partially. It is harder to clean thoroughly. Refilling means getting the vehicle to the water or carrying a jug to transfer. And a plumbed system has pumps, hoses, and fittings that can fail or leak, sometimes into the interior.

What most builds land on

The setup that tends to work best is a hybrid: a moderate fixed tank for daily use with a tap, plus one or two jugs as reserve and for refills. You get the efficiency of a tap for cooking and washing, an independent backup if the tank system fails, and a way to top up without repositioning the truck.

Where the weight goes

This is the part that gets skipped, and it matters more than the container choice.

Water is dense, and it moves. A partially full tank has a free surface that sloshes, and that sloshing load transfers to the mounting points and to the vehicle’s handling. Two rules:

Low and between the axles. The ideal location is as low as possible and as close to the middle of the wheelbase as you can manage. Under the bed, under a rear seat, or in the bottom of a drawer module. This is the same logic covered in roof racks and payload — mass up high or far back hurts you twice, once in handling and once in what it does to your suspension.
Never on the roof. A 20-gallon tank on a roof rack is 170 pounds at the worst possible height, and it will noticeably change how the vehicle behaves on side slopes. If the only place it fits is the roof, carry less water.

Behind the rear axle is the other spot to avoid where you can. Weight there acts on a lever, unloading the front end and making the rear feel loose. A rear bumper-mounted jug or two is fine; 25 gallons hanging off the back is not.

Mounting properly

Unsecured water is dangerous. A 7-gallon jug is 58 pounds, and in a sudden stop it becomes 58 pounds moving at whatever speed you were doing.

Secure every container so it cannot move in any direction, including up. Ratchet straps through a proper anchor, a dedicated jug holder, or a tie-down in a storage system — not a bungee.
Support a fixed tank across its whole base rather than at a few points. Tanks are designed to be cradled; point loads on a full tank flexing over washboard is how they crack at the seams.
Use baffled tanks if you can, or keep tanks either mostly full or mostly empty. A half-full unbaffled tank is the worst case for both sloshing and mount stress.
Plumb with a shutoff at the tank, and route hoses where a failure drains outside the vehicle rather than into your electrical or your bedding.

Keeping it drinkable

Water does not spoil on its own. What ruins it is what grows in it, and that comes down to light, warmth, and time.

Use opaque containers. Light drives algae growth. Clear or translucent jugs left in the sun will go green. This is the single most common cause of nasty-tasting stored water.
Use food-grade containers only — look for HDPE marked for potable use. A container that held something else, or a non-food-grade plastic, can leach into the water and hold flavors permanently.
Rotate it. Fresh municipal water stored cool and dark is fine for months, but there is no reason to find out. Dump and refill before each trip. It costs nothing.
Clean the system periodically. A dilute bleach solution circulated through tank, pump, hose, and tap, left to sit, then thoroughly flushed, will reset a system that has started to taste off. Do the whole path, not just the tank — biofilm in a hose will recontaminate a clean tank immediately.
Dry containers between trips if they are going to sit. Stored damp and sealed is how a jug develops a smell you cannot get out.

Filtration and treatment: what you actually need

These solve different problems and people conflate them:

A sediment or carbon inline filter on the tap improves taste and catches grit. It does not make questionable water safe. Worth having; not a safety device.
A pump-style or gravity backpacking filter removes bacteria and protozoa. This is what you want for refilling from a creek or a stock tank, and it is the single most useful item for extending range, because it converts “find a spigot” into “find any water.”
Chemical treatment (tablets or drops) is light, cheap, slow, and tastes bad. Perfect as a backup that lives in the kit and never gets used.
UV pens work on clear water only and need batteries. Fine as a secondary.

For most overland travel in developed areas, a filter for opportunistic refills plus chemical backup covers everything realistically. If you are drawing from surface water regularly, invest in the filter rather than more tank capacity — it weighs a fraction as much and multiplies your range.

The details that make it pleasant

A few things that separate a water setup you enjoy from one you tolerate:

A tap you can operate hands-free — a foot pump or a switch — because you will wash your hands far more often when you do not have to hold a jug.
A drain point. Being able to empty the tank completely without disassembly is what makes cleaning it likely rather than theoretical.
A sight gauge or a known-volume marker. Guessing how much water is left is how people ration unnecessarily or run out unexpectedly.
Freeze protection. Water expands when it freezes and will split a full tank or a pump housing. In real cold, either drain the system or keep it inside the heated space.
A separate small bottle for grey use — dish rinse, hand rinse — so you are not dipping into drinking supply for chores.

The short version

Plan a gallon per person per day for drinking and cooking, add half again for washing, then add a full day in reserve you do not count. Carry it low and between the axles, never on the roof, and secure every container as if it will try to move, because it will.

Jugs win on flexibility and simplicity; a plumbed tank wins on convenience and water efficiency. Most good setups use both. Keep it in opaque food-grade containers, rotate it before every trip, clean the whole path and not just the tank, and carry a real filter so that any water source extends your range.

The portable water collection has the tanks, jugs, pumps, and taps, and the camping accessories collection covers the rest of the camp setup that water feeds into.