- Top Pick: RV Fresh Water Tank, Sptinter 2500 & Transit 33-Gallon Non-Standard RV Wheel Well Water Storage Tank Tailored for Sprinter 2500 & Transit Vans(Drivers Side)
- Best Value: TORVA 33-Gallon Non-Standard RV Wheel Well Fresh Water Storage Tank for Drinking, Cooking, Cleaning, Showering, Tailored for Sprinter 2500 & Transit Vans
- Premium Choice: Class A Customs | UM-2000 | One (1) UnderMount 20 Gallon RV Fresh and Gray Water Holding Tank RV Concession
Last updated: September 18, 2026
The Short Answer
For most van builds, a 20- to 30-gallon fresh-water tank is the practical sweet spot. It gives one or two people enough water for cooking, drinking, handwashing, dishes, and occasional showers without consuming too much storage space or payload.
Use this quick guide when deciding what size water tank for van life:
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- 10–15 gallons: Weekend trips, simple cooking, no indoor shower, frequent refill stops.
- 20 gallons: One person for roughly 4–7 days, or two people for 2–4 days with careful use.
- 25–33 gallons: A strong choice for couples, shower-equipped vans, or longer stretches away from campgrounds.
- 35–45 gallons: Extended off-grid travel, families, pets, or regular indoor showers.
Water is heavy: 1 gallon weighs about 8.34 pounds. A full 20-gallon tank adds roughly 167 pounds before counting the tank, fittings, pump, and plumbing. A full 33-gallon tank adds about 275 pounds. Choose a capacity that fits your travel habits, available space, and van’s payload rating—not simply the largest tank you can squeeze in.
For 2026 van conversions, slim underfloor tanks and wheel-well tanks remain especially useful because they preserve valuable cabinet and garage space.
Standard Sizes
See also: Best Van Water Filter for Refill Stations in 2026: Tested and Ranked • How to Winterize a Van Water System (2026): Step-by-Step
RV water tanks are not standardized to one exact shape. Two tanks with the same gallon rating can have very different footprints, especially wheel-well and undermount designs. The measurements below show common usable outside dimensions for rectangular or low-profile tanks; always verify the exact product drawing before cutting cabinetry or drilling mounting holes.
| Nominal Capacity | Typical Tank Dimensions (L × W × H) | Metric Dimensions (L × W × H) | Water Weight When Full | Best For |
|---|---|---|---|---|
| 5 gallons | 20 × 10 × 6.5 in. | 50.8 × 25.4 × 16.5 cm | 42 lb. | Portable use, day trips, backup water |
| 10 gallons | 24 × 12 × 8 in. | 61.0 × 30.5 × 20.3 cm | 83 lb. | Weekend solo trips |
| 15 gallons | 30 × 15 × 8 in. | 76.2 × 38.1 × 20.3 cm | 125 lb. | Minimalist solo or couple travel |
| 20 gallons | 40 × 14 × 9 in. | 101.6 × 35.6 × 22.9 cm | 167 lb. | Compact indoor or low-profile undermount installation |
| 25 gallons | 42 × 18 × 9 in. | 106.7 × 45.7 × 22.9 cm | 209 lb. | Couples without daily showers |
| 30 gallons | 45 × 20 × 8 in. | 114.3 × 50.8 × 20.3 cm | 250 lb. | Longer trips and shower-capable vans |
| 33 gallons | Approx. 52 × 12 × 17 in. wheel-well profile | Approx. 132.1 × 30.5 × 43.2 cm | 275 lb. | Sprinter and Transit wheel-well builds |
| 40 gallons | 48 × 24 × 9.5 in. | 121.9 × 61.0 × 24.1 cm | 334 lb. | Extended off-grid travel |
A 20-gallon undermount tank is often a good starting point for compact layouts. For example, under-mount tanks in this capacity commonly cost about $120–$170, while vehicle-specific 33-gallon wheel-well tanks typically run about $245–$260. The higher price reflects the molded shape that fits around a van’s wheel arch.
How to Measure Your Space
- Choose the tank location first. Common locations include under the bed, inside a lower cabinet, between frame rails, beneath the van, or over a rear wheel well. Interior tanks are easier to protect from freezing; exterior tanks free up living space.
- Measure the clear footprint. Record the maximum length, width, and height in inches. Measure at several points because van walls, wheel wells, ribs, and floor contours are rarely square.
- Leave installation clearance. Add at least 1 inch around the tank body for straps, mounting brackets, insulation, and minor movement. Leave more room near fittings, drain ports, and fill connections.
- Account for plumbing. A tank needs room for a fill hose, vent hose, pickup fitting, overflow, drain valve, and water-line connection. Do not position a fitting directly against a wall or floor.
- Check service access. You should be able to inspect fittings, tighten a clamp, clean the tank, and reach the drain without removing half the build.
- Calculate full weight. Multiply gallons by 8.34, then add the tank’s empty weight. Confirm that the tank location and mounting system can safely support that load while driving.
- Mock it up. Use cardboard, painter’s tape, or a plywood box matching the tank’s exterior dimensions. Test bed height, cabinet doors, garage access, and walking clearance before ordering.
By Room or Use Case
Weekend Van or Minimalist Setup
A 10- to 15-gallon tank works well when you mostly use campground restrooms, eat simple meals, and travel where refills are easy. This size fits beneath a bench, in a galley cabinet, or under a low bed platform. Plan on about 1 to 2 gallons per person per day for drinking, basic cooking, and quick cleanup.
If you use portable water jugs instead of a permanent tank, two 5-gallon containers can be easier to carry and refill. The tradeoff is a less streamlined plumbing system and more frequent water stops.
Solo Full-Time Van Life
A 20- to 25-gallon tank suits many solo travelers. It supports a sink, drinking water, dishes, brushing teeth, and conservative shower use. With a low-flow shower head and navy-style showers—wet down, turn water off, soap up, rinse—20 gallons can last several days.
For a compact build, a 20-gallon tank mounted low and close to the van’s center helps control weight distribution. Avoid putting a full tank high in an upper cabinet; 167 pounds of moving water is not appropriate overhead.
Couples and Shower-Equipped Vans
Choose 25 to 33 gallons if two people travel together, cook most meals in the van, or want a usable indoor or rear-door shower. A 33-gallon wheel-well tank can be an efficient choice in a Sprinter 2500 or Ford Transit because it uses a difficult-to-cabinet area along the van side.
Vehicle-specific 33-gallon wheel-well tanks generally cost around $250. Before buying, verify whether the model is designed for the driver’s or passenger’s side, the wheelbase, and the exact van generation. A few inches of difference in a wheel arch can prevent a molded tank from fitting.
Extended Off-Grid Travel, Pets, or Families
Consider 35 to 45 gallons for longer stays on public land, regular showers, large dogs, or more than two travelers. This capacity can be practical, but it requires thoughtful placement. Forty gallons of water weighs about 334 pounds, and a large gray-water tank may add similar weight if you carry wastewater instead of draining it at approved stations.
Many long-term travelers prefer two smaller tanks rather than one very large tank. For example, a 20-gallon primary tank plus a 10-gallon reserve lets you isolate water if one tank or fitting develops a problem.
Common Sizing Mistakes
- Buying based on gallons alone: A 33-gallon tank may fit around a wheel well but not under your bed. Compare the full dimensional drawing, including fitting locations.
- Forgetting water weight: Water capacity affects payload, suspension behavior, braking, and tire loading. Keep heavy tanks low and near the vehicle’s center whenever possible.
- Ignoring gray-water capacity: If you have a sink or indoor shower, plan where wastewater will go. A 30-gallon fresh tank paired with a 5-gallon gray tank creates an impractical imbalance.
- Not allowing for freezing conditions: Exterior tanks, exposed plumbing, and fittings can freeze. If you camp below freezing, an interior fresh tank is usually easier to protect.
- Oversizing for occasional needs: Carrying 250 to 330 pounds of water every day may not make sense if you refill every two or three days. More capacity is useful only when you will actually use it.
- Skipping a vent and drain plan: A tank needs proper venting while filling and a reachable low-point drain for cleaning and winterizing.
FAQ
How many gallons of water do I need for van life?
A practical estimate is 2 to 4 gallons per person per day. Use the lower end if you do not shower in the van and refill often. Use the higher end if you cook daily, travel with pets, wash dishes frequently, or use an onboard shower.
Is a 20-gallon water tank enough for van life?
Yes, for many solo travelers and short trips. A 20-gallon tank provides about 167 pounds of water and can last one careful traveler 4 to 7 days. Couples who shower in the van will usually be happier with 25 to 33 gallons.
Where should a fresh-water tank go in a van?
The best location is low, secure, and close to the van’s center of gravity. Under-bed garages, low cabinets, and purpose-built wheel-well spaces are common interior locations. Undermount tanks save interior room but need protection from road debris and cold weather.
Should my gray-water tank be the same size as my fresh-water tank?
Not necessarily, but it should match your habits. If nearly all fresh water goes down the sink or shower drain, gray capacity should be close to fresh capacity. If you drink bottled water, use campground showers, or dump dishwater responsibly where permitted, a smaller gray tank may be sufficient.
Ready to decide? Our #1 pick for 2026 is the 5 gallons.
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