Water Tank Placement in Vans: Wheel Well vs Spare Tire vs Undercarriage

Why Water Tank Placement Matters

Every van conversion centers around how space is used and water storage significantly influences that. Water tanks add weight, require plumbing, and need periodic servicing. The chosen location affects interior layout, how stable the vehicle drives, how you combat freezing in cold weather, and how accessible the tank is for maintenance or expansion.

While capacity numbers often win attention, placement sets the foundation of how you interact with your van daily. A misjudged decision can limit your cabinetry design or frustrate you when plumbing becomes overly complicated. By contrast, a well chosen tank location elevates both form and function. Here, we explore three placement styles, each with unique strengths and trade offs, with the focus on helping you understand how placement relates to your van’s layout and use.

Wheel Well Water Tank Placement

Wheel well tanks are molded to the curved contours of rear wheel arches inside your van. They take up space usually reserved for awkward storage and offer an intelligent way to conceal water volume near the rear axle.

People frequently choose wheel well placement when they value interior practicality and ease of plumbing. The tank sits inside the insulated part of the van, which helps minimize freezing in colder temperatures. Since it is centered roughly over the rear axle, it contributes to balanced weight distribution and predictable handling even when full.

Serg Supply offers multiple wheel well tank options, including a 33 gallon Sprinter model for the driver side, a lighter 20 gallon Sprinter version, vehicles with dual rear wheels can utilize the 25 gallon dually tank, and there are also tailored models for Transit and Promaster platforms. These tanks integrate well with cabinetry or garage storage and are often paired with floor access or side hatch plumbing.

The trade off is that wheel well tanks reduce space in the rear cargo area. If your build includes long drawers, bike storage, or a rear bench, you’ll need to plan around the tank shape. But for builders needing higher capacity paired with cabin access and weather resistance, wheel well placement is often the ideal choice.

Spare Tire Water Tank Placement

For vanlifers who have moved their spare tire to an external carrier or simply don’t need it, spare tire mounted tanks offer substantial capacity while leaving the interior completely intact. These tanks fit into the factory spare tire location or use engineered mounts to anchor under the rear bumper.

The major appeal is that the interior layout is not impacted by the tank, your living space remains totally available for insulation, cabinetry, gear, or sleeping platforms. Serg Supply provides a 28 gallon tank designed specifically for Sprinter 2500, Winnebago Revel, and Storyteller platforms, which fits using factory hardware. For Transit van builds, their 24 gallon spare tire tank comes with its own hardware and precise fitment.

With spare tire placement, water capacity is generous and doesn’t interfere with access halls, living areas, or gear compartments. But these tanks are mounted outside the van, making them more exposed to road debris, moisture, and temperature extremes. Installation may require relocating the spare tire to a swing arm mount or roof rack, and in cold climates, additional insulation or a heat tape system becomes important. Servicing also requires under vehicle access, which may be less convenient than interior compartments.

Still, for builds where preserving interior volume is the top priority, or when designers are focusing on maximum tank size without losing space in the van, spare tire tanks provide a compelling solution.

Undercarriage Water Tank Placement

Undercarriage tanks are installed beneath the van, typically along one side or under the sliding door. They remain fully underneath the vehicle, making them invisible in the living area and preserving interior arrangement entirely.

This placement style suits builders who prioritize layout flexibility and clear floor plans. It also contributes to a lower center of gravity, which may offer improved driving stability. Serg Supply offers undercarriage tanks such as an 11 gallon Sprinter tank under the slider door, a 22 gallon Sprinter side tank near the fuel tank, a 16 gallon Transit model, and a 20 gallon version for more volume.

Owners often use these tanks for fresh water or grey water. Their capacity is generally smaller than wheel well or spare tire tanks, so it's ideal for moderate consumption or when paired with additional tanks. Undercarriage placement requires thoughtful installation: secure stainless steel straps, correct plumbing through the floor, and proper venting to avoid suction or overflow. And because the tank is outside thermal insulation, freeze protection becomes more critical, particularly in colder regions or in high altitude camping environments.

While tanks under the vehicle may accumulate road grit or pitting over time, correct mounting and periodic inspection reduce concerns. For many vanlifers who don’t need the most gallons onboard and value usable interior space over sheer capacity, undercarriage placement is a strategic and flexible option.

Comparison Table: Tank Placement Overview

Choosing the Right Placement for Your Van Lifestyle

Selecting a water tank placement depends on how you plan to live and travel in your van.

If you’re embarking on year round adventures and camping in varied climates, the wheel well tank is often the safest bet. It delivers high capacity, better insulation, and cab access for maintenance. For example, a full time van builder using the Sprinter 33 gallon tank can reduce refill stops and maintain more consistent water temperature in cold weather.
If your van layout is already packed with gear, cabinetry, or modular components, especially if you’ve moved the spare tire, then the Spare Tire Tank offers a clean solution with zero space impact. Perfect for mid length trips with plenty of storage.

For those focusing on a minimalist or adaptable interior, undercarriage tanks allow you to keep floor space wide open while still carrying enough water for moderate use. Using the Sprinter 22-gallon or Transit 20-gallon models gives you flexibility without compromising cabin layout.

Many builders combine placements for instance, pairing a wheel well fresh water tank with an undercarriage grey water tank to balance capacity, access, and interior space.

Final Thoughts

Whether you choose wheel well, spare tire, or undercarriage placement, the tank location sets the tone for the rest of your build. Take your layout goals, climate expectations, and routine into account before finalizing.

The Northwest Conversions tanks available at SergSupply include carefully engineered models for all three placements across Sprinter, Transit, and Promaster vans. Their shapes and port options fit exactly where they need to, giving vanlifers flexibility and consistency.
If you haven’t chosen a location yet, reflect on how you’ll access your tank, how you’ll protect it from freezing, and how it integrates into your interior design. Thoughtful placement now saves headaches later and creates a more reliable, comfortable experience on the road.

Explore the full Northwest Conversions water tank collection at SergSupply, and find what tank matches your build goals.