Wheel Well vs Undermount Water Tanks
Which Is Better for a Camper Van Build
Wheel well tanks and undermount tanks both work well, but they solve different problems. The right choice depends on layout, climate, service access, and how you actually plan to use your van. Given that the price is essentially the same, there can be anxiety figuring out which water tank will work best.
This article compares wheel well vs undermount water tanks so you can choose confidently without guessing.
Why Do You Want a Wheel Well Tank Versus an Undermount Tank
This decision usually comes down to layout. A wheel well tank makes use of interior space that already exists and keeps water inside the heated envelope of the van. An undermount tank frees up interior storage but exposes the tank to outside temperatures and road conditions.
Neither option is universally better. Each has clear advantages depending on how the van is built and used.
What Is a Wheel Well Water Tank
Wheel well water tanks are molded to fit over the factory wheel arch inside the van. They maximize volume in an irregular space and allow plumbing connections to stay inside the living area. Because they are interior tanks, they benefit from insulation and cabin heat.
Most wheel well tanks are used as fresh water tanks.
What Is an Undermount Water Tank
Undermount water tanks are mounted underneath the van using rigid brackets or straps tied into factory structure. They are designed for the driver side, passenger side, and spare tire areas underneath the van. They are commonly used for gray water, and sometimes for fresh water in warmer climates or seasonal builds (mainly at the spare tire location). Undermount tanks reduce interior clutter and allow gravity drainage.
Because they are exposed, freezing protection must be planned intentionally.
Climate Is the Biggest Differentiator
If you travel in cold weather, wheel well tanks are usually the safer choice for fresh water. Interior tanks are far less likely to freeze as long as the cabin is heated. This is why four season builds almost always place fresh water inside the van. Undermount tanks can work in winter, but they typically require heating pads, insulation, or seasonal draining.
Layout and Interior Space Considerations
Wheel well tanks consume interior volume, usually inside cabinets or benches. In many layouts, this space is already difficult to use efficiently, which makes wheel well tanks a natural fit. Bigger tanks take up more space or raise the height of a bed system or galley. Undermount tanks preserve interior storage but can limit where plumbing exits the floor.
The best choice depends on cabinet layout and how tight your build is. We have a water tank configurator, where you can input a variety of dimensions and find the best tank for your build layout.
Plumbing Complexity and Service Access
Wheel well tanks are easier to plumb because all fittings remain inside the van. Undermount tanks require plumbing lines to pass through the floor and be protected from road exposure. Service access is still good when designed well, but it requires more planning.
Builders often keep fresh water inside and gray water outside to balance complexity.
Weight Distribution and Driving Feel
Water is heavy regardless of location. Wheel well tanks place weight higher but closer to the center of the van. Undermount tanks place weight lower, which can help handling. In general, with the other weight of the build considered this is a minimal impact or consideration on tank decisions. In practice, both work well when tanks are sized appropriately.
Typical Real World Tank Pairings
Many builders land on a hybrid setup that uses a wheel well fresh water tank and an undermount gray water tank.
This approach keeps potable water protected while freeing interior space and simplifying drainage.
Using a Configurator to Compare Options
Choosing between wheel well and undermount tanks is easier when you can see combinations laid out clearly. The GoCode Overland water tank bundle configurator allows you to compare tank sizes, locations, mounting hardware, and plumbing components together in one place.
It helps builders visualize how different setups affect layout and winter planning before committing.
You can explore it here:
https://gocodeoverland.com/pages/water-tank-bundle-configurator
Used correctly, tools like this reduce guesswork and prevent buying the wrong tank first.
Which Option Is Better Overall
There is no universal winner. This decision will come up to your layou dimensions, ideal water capacity, and temperature constraints.
The best systems are intentional, not copied.
Final Thoughts on Wheel Well vs Undermount Tanks
This decision sets the foundation for your entire water system. By considering climate, layout, service access, and freezing risk early, you avoid costly changes later. Most builders who plan carefully end up with a mixed system that uses both styles where they make the most sense.
