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Water Systems in Van Builds

Van plumbing breaks down into up to three separate systems: fresh water (clean), grey water (used), and black water (toilet waste). Not every build needs all three — most Basic and Standard builds skip black water entirely.

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Fresh Water System

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Components

  • Tank: Polyethylene (food-grade) tanks in 15–50+ gallon sizes. Mounted under the van (common) or inside a cabinet (smaller builds).
  • Fill port: External fill port or a cap on top of the tank. External fill ports let you fill up without opening anything inside the van.
  • Pump: 12V diaphragm pump. Shurflo and Seaflo are the most common. 3–4 GPM is standard for most builds.
  • Accumulator tank (optional): A small pressurized tank that smooths out pump cycling. Without one, the pump kicks on and off rapidly with each short burst of water. Not required, but nice to have.
  • Filter: An inline sediment filter before the pump protects it from debris. A second drinking water filter (carbon block) at the kitchen faucet improves taste.
  • Lines: 1/2” PEX for main runs, 3/8” PEX for individual fixture connections.

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Layout

The typical flow is: Tank → filter → pump → manifold → individual fixture runs. A manifold lets you branch off to the kitchen sink, shower, and any other fixtures from a central point. This makes troubleshooting easier and keeps the plumbing organized.

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Filling Up

You can fill your fresh tank at any RV dump station with a potable water spigot, at campgrounds, or from a garden hose at home. A simple garden hose quick-connect on your fill port makes this easy.

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Grey Water System

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What It Is

Grey water is everything that goes down a drain — dish water, shower water, hand washing. It’s not sewage, but it’s not clean either.

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Components

  • Tank: Mounted underneath the van using straps or a custom bracket. Size it to match your fresh water tank (if you have 30 gallons of fresh, you want at least 25–30 gallons of grey).
  • Drain lines: 3/4” or 1” PEX or flexible hose from each drain to the grey tank.
  • P-traps: Installed on every drain line to prevent odor backflow from the tank.
  • Dump valve: A gate valve at the bottom of the grey tank. Open it at an RV dump station to empty.
  • Vent: Grey tanks need a vent to prevent vacuum lock when draining and to allow air displacement when filling.

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Tips

  • Mount the grey tank at the lowest accessible point under the van so water drains by gravity.
  • Insulate the grey tank and drain lines if you’ll be in freezing temperatures.
  • Use a tank level sensor (or just track how much fresh water you’ve used) so you know when it’s time to dump.

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Black Water System

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When You Need It

Only Premium builds with a full bathroom typically include a black water system. Most builds skip it entirely — a composting toilet or cassette toilet handles waste without plumbing.

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Options

  • Composting toilet (Nature’s Head, Separett) — No plumbing required. Separates liquid and solid waste. Most popular option for van builds because it’s simple and self-contained. Not technically a “black water system” since there’s no tank.
  • Cassette toilet — A removable waste cartridge that you empty at dump stations. Compact and works well for occasional use.
  • Black water tank — A dedicated waste tank plumbed to a flush toilet. This is how RVs do it, but it takes up space, adds weight, and requires an RV dump station to empty. Rare in van builds except for large Sprinter 170” Extended rigs with full bathrooms.

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Water Quality

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Filtration

At minimum, use a sediment pre-filter before your pump. For drinking water, add a carbon block filter on the kitchen cold water line. Brands like Clearsource or Hydroviv make good inline filters.

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Tank Maintenance

  • Sanitize your fresh tank every 3–6 months with a diluted bleach solution (1/4 cup bleach per 15 gallons), run it through the lines, let it sit for a few hours, then flush thoroughly.
  • Don’t let water sit in the tank for more than 2 weeks without use — stagnant water breeds bacteria.

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Next Steps