ARTICLE: Fresh vs Grey Water Tank Sizing for Camper Vans

Last updated: November 3, 2026

Size fresh and grey tanks together. A common starting point for solo full time use is 20 to 24 gallons fresh with 11 to 16 gallons grey, and 24 to 36 gallons fresh with 16 to 22 gallons grey for couples or frequent showers. Grey fills fastest because nearly all used water ends up there. These are guidelines, not rules

Fresh vs Grey

Fresh tanks hold potable water for drinking, cooking, dishes, and showers. Gray tanks collect water from sinks, showers, and drain pans. They're one system.

Typical Fresh Sizes

  • 10 to 15 gallons: weekend and minimalist

  • 20 to 24 gallons: full time solo

  • 30 to 36 gallons: couples or frequent showers

Typical Grey Sizes

  • 7 to 11 gallons: sink only

  • 16 to 22 gallons: sink and shower

Ratios

  • Equal capacity: daily showers

  • Fresh about 1.5x grey: sink-heavy builds

  • Grey much smaller: only with conservative use, recycling, or out of van dumping

Recycling Showers

Recycling showers let both tanks be smaller. A common pairing is 20 gallons fresh and 11 to 16 gallons grey.

Weigh the Tradeoffs

  • Weight: water is about 8.3 lb per gallon. A full 36-gallon tank adds nearly 300 lb.

  • Space: bigger tanks need bigger cabinets.

  • Climate: cold-weather builds often favor interior fresh tanks for freeze protection.

  • Dumping: rules vary by location. A larger grey tank gives more flexibility.

  • Maintenance: larger tanks take longer to clean.

Key Takeaways

  • Plan fresh and grey together.

  • Grey is usually the limiting tank.

  • Add a shower, and grey capacity matters most.

  • Aim for balance, not maximum capacity.

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