Gear
Water is the heaviest thing you carry and the first thing that turns a bad day into an emergency. Here is how much, and how to keep it drinkable.
Everything else on a vehicle can be improvised. Water cannot. It is also the single heaviest item in most builds, which means the question is never "how much can I fit" but "how much do I actually need, and what does that weigh on the rear axle".
This guide gives the figures the land agencies publish for desert travel, what water weighs, how to keep a tank clean, and exactly what the CDC and the EPA say about treating water you find. It names no products.
Mojave National Preserve tells drivers to take "a minimum of one gallon of water per person per day (two gallons if you are hiking during hot weather), and drink it freely", and to carry extra drinking water for emergencies. Death Valley says the same: at least a gallon a day to avoid dehydration, and extra food and water in case you are stranded.
That is the floor for drinking in heat, not for cooking, washing or a dog. A useful working figure is a gallon and a half per person per day for a desert trip where you will also cook and rinse a pan, and more if you plan to wash.
Then add the margin that matters: enough to sit still. The Park Service tells stranded drivers in Death Valley to stay with the vehicle, because rescue on a backcountry road is "likely to be extremely delayed". Your water should cover the day you planned plus the day you did not.
Working the number out
Water weighs 8.33 pounds a gallon, so 20 gallons is 167 pounds before the tank, the pump and the plumbing. That is a serious fraction of the payload of most four-wheel drives, and all of it is liquid that moves.
Mount it low and between the axles if you can. Water high on a rack raises the centre of gravity of the heaviest thing you own; water hung off the back tailgate puts it all behind the rear axle, which lightens the steering. A part-full tank without baffles will slosh hard enough to feel in a corner, so either fill it or use several smaller containers.
Carry it in more than one vessel whatever else you do. A single tank is a single failure: a cracked fitting on a washboard road empties everything you have. Two containers and a third small one in the cab is a system that survives a mistake.
The CDC is specific about containers. Use food-grade storage containers, which "will not transfer toxic substances into the water", and never a container that has held a toxic chemical such as bleach or a pesticide.
To prepare one, wash it with soap, rinse it, then sanitise it with a solution of one teaspoon of unscented household chlorine bleach (5 to 9 percent sodium hypochlorite) in one quart of water. Cover and shake so the solution touches every surface, wait at least 30 seconds, pour it out and let the container air dry.
Label it as drinking water with the date, replace the water every six months, and keep it between 50 and 70 degrees, out of direct sun and away from petrol and pesticides. Draw from it with something clean, and do not put your hands inside it.
The CDC is blunt about the mountain stream: drinking straight from a clear one "is generally not safe". Treat everything.
Boiling is the best method. Bring clear water to a rolling boil for one minute, or three minutes above 6,500 feet, and let it cool. The EPA gives the altitude as 5,000 feet rather than 6,500, so on a high trip use the stricter figure and boil for three. If the water is cloudy, let it settle and filter it through a clean cloth or a coffee filter first.
Where boiling is impractical, filter and then disinfect. What a filter removes depends on its pore size: one micron or smaller (or certified to NSF standard 53 or 58 for cysts) removes parasites but not viruses or all bacteria; 0.3 micron or smaller removes bacteria and parasites but not viruses; reverse osmosis removes all three. Chemical disinfectants are the mirror image: they kill viruses and bacteria but may not kill parasites, which is why the CDC says filter first, then disinfect.
Ultraviolet units kill parasites, bacteria and viruses in small amounts of clear water, but do not work well in cloudy water. Iodine is not for everyone: the CDC says people who are pregnant, have thyroid problems or are sensitive to iodine should avoid it, and nobody should drink iodine-treated water for more than a few weeks.
Do not skipNo amount of boiling or disinfecting makes water contaminated with chemicals, toxins or radioactive material safe. Downstream of a mine, a mill or farmland, treat the water as undrinkable and carry what you need.
The EPA publishes the emergency ratio: use regular unscented chlorine bleach whose label gives 6 or 8.25 percent sodium hypochlorite, stored at room temperature for less than a year. Add 8 drops of 6 percent bleach, or 6 drops of 8.25 percent, to each gallon of clear water. Double it if the water is cloudy, coloured or very cold.
Stir and let it stand for 30 minutes. The water should have a slight chlorine smell. If it does not, repeat the dose and wait another 15 minutes. Do not use scented, colour-safe or cleaner-added bleach. With tablets, follow the label, because strengths differ.
The rule that protects both the water and your welcome is distance. Leave No Trace, as the Park Service publishes it, is to carry water 200 feet away from streams and lakes to wash yourself or your dishes, use small amounts of biodegradable soap, and scatter the strained dishwater. Camp at least 200 feet from lakes and streams for the same reason.
The federal rules behind that are plainer still. In a national park it is prohibited to drain refuse from a vehicle except at a facility provided for it, and to wash food, clothing or dishes at a public water outlet not designated for it. On national forest land it is prohibited to fail to dispose of waste water properly. On Bureau of Land Management ground you may not drain sewage or dump waste other than wash water from a vehicle except where provided.
The practical version: strain the solids into your rubbish, scatter the water well away from any stream, and never empty a tank on the ground at a campsite.
Containers and filters come from outfitters and camping equipment shops. A plumbed tank, a pump and a sink belong to the same trade as the electrical system, so a van or RV service centre or the builder who did the interior is the place for that work.
Whoever fits it, ask where the tank sits in relation to the axles, how it is secured, and how you will drain and clean it. A tank you cannot empty and dry is a tank that will eventually taste of it.
At least one gallon per person per day for drinking, or two if you will hike in hot weather, which is what the Park Service publishes for Mojave and Death Valley. Add cooking and washing, and carry a full extra day beyond your plan.
A gallon weighs 8.33 pounds, so 20 gallons is 167 pounds before the tank and plumbing. Check that against your vehicle's payload.
Bring clear water to a rolling boil for one minute. The CDC says three minutes above 6,500 feet; the EPA says three above 5,000 feet. Use the stricter figure if you are high up.
It depends on the filter. Most portable filters remove parasites but not viruses or all bacteria. A 0.3 micron filter adds bacteria. Only reverse osmosis removes viruses too. The CDC's advice is to filter first and then disinfect.
At least 200 feet from any lake or stream, with a small amount of biodegradable soap, scattering the strained water. Washing at a campground's drinking water tap is prohibited in national parks.
Reviewed September 19, 2026. Conditions, closures and rules change; check with the managing agency before you travel.