Fresh water tank sizing

Calculate, then observe

Daily gallons = drinking + cooking + dishes + hygiene + showers + toilet + pet + cleaning. Multiply by off-grid days, then add a reserve. A two-person full-time van can vary from roughly 5-15+ gal/day depending mainly on showers and dishes.

Usable is not advertised

Tank shape, outlet position, slope, venting and parking angle leave water behind. A nominal 40 gal tank may not provide 40 gal at the pump. Verify fill volume and pump-out volume during commissioning.

Tank choice

Use documented potable-water material. Opaque tanks reduce light/algae risk; translucent tanks make level visible but need darkness. Internal tanks freeze less; underslung tanks preserve living space but face cold, impacts and road contamination.

Mounting

Support the entire wet weight across the tank design, prevent movement in every direction and follow the tank maker's support requirements. Do not hang a non-approved tank by fittings. Baffles can reduce slosh in long tanks. Provide vent, full drain and cleanout if the design permits.

Weight example

A 40 US gal fill weighs about 334 lb / 151 kg . Add tank, supports, heater water, grey water carried at the same time and occupants/gear. Verify actual axle weights when loaded for travel.

CHAPTER CHECK

• I can explain the purpose and failure mode of each item in this chapter. • I know which manufacturer limit or water-quality claim controls my choice. • I added the valve, access, drain, measurement or maintenance task to my drawing/checklist.