Camper and RV Fresh Water Tank Options

Picking a water tank is typically one of the first steps in a new camper build. The size, shape and location of the tank dictates quite a few subsequent design decisions.

A few questions to consider: Are you going to mount inside or outside the vehicle? Are you going to try and optimize space by using a wheel well shaped tank? What material do you want the tank to made of? How much water do you need?

How much water do you need?

Deciding on how much water capacity is needed is your first decision, since this will shape the next set of decisions. Use our handy camper van water consumption calculator to get you a rough idea of your requirements.

Inside or Outside the Vehicle?

Each option here has its drawbacks. Outside (under) the vehicle is great for saving precious in-vehicle space, but is obviously a problem if you’re spending time in freezing temperatures. You might also be capacity-limited under the vehicle, as finding a suitable mounting location for a large tank might difficult if not impossible.

Inside the camper is clearly using space that could otherwise be dedicated to other necessities or nice-to-haves. Temperature is not a problem with internal storage, assuming the tank is exposed to warmer in-vehicle air.

Another option, which I’ve not yet seen, is a hybrid approach using 2 tanks. In warm climates, both tanks could be used simultaneously for high-volume storage, and the external tank could be deactivated and drained for sub-zero climate.

Tank Shape

Typical cuboid-shaped tanks are incredibly common, and are easy to design around.

There are quite a few different dimensions available, and you’re almost certain to find the right dimensions for your build. Here are a few examples:

Under Mount 20
48″ x 8.5″ x 13″

Under Mount 30 Gallon
48″ x 8.5″ x 20.5″

Due to the underslung nature, these under mount tanks tend to be shorter and longer than interior tanks.

30 Gallon Interior Tank
34.5″ x 12″ x 17.5″

40 Gallon Interior Tank
39 1/2″ x 13″ x 18″

65 Gallon Interior Tank
44.5″ x 17.5″ x 19.5″ (That is one big tank)

Amazon has an assortment of other shapes and sizes.

In the past few years some newer and more interesting configurations have emerged, including on over the wheel well configuration. What makes this interesting is that this shape utilizes space that is often wasted due to the awkward shape created by the rear wheels.

A number of manufacturers supply these tanks, including Northwest Conversions, National Tank Outlet, Agile Offroad, and Titan DIY Kits.

Plastic vs. Stainless Steel Water Tanks

Plastic tanks are by far the most common for DIY camper van builds, and are significantly less expensive than a stainless tank. One major benefit of the stainless tanks is that they’re easier to have custom fabricated. If you have a particular shape or size that you absolutely must have, and are willing to pay, you could get a custom tank that suits your needs perfectly.