VAN-COMPARATOR Guide
Water on board an RV: filling up, saving it, draining it
Fresh water tank, grey water, toilet cassette: where to fill, how to last 3 days on 100 litres and where to drain legally across Europe.
A motorhome's autonomy is measured less in kilometres than in litres. Understanding the water circuit — fresh, grey, black — is the number-one skill of vanlife, and the one rental companies explain too quickly at key handover.
The three tanks
- Fresh water: 100–150 litres on a semi-integrated or A-class motorhome, 40–100 on a campervan. Feeds the sink, the shower and sometimes the toilet.
- Grey water: washing-up and shower water, collected under the floor (typically 90–100 litres). Drained via a valve, over a dedicated grate.
- Toilet cassette (black water): a removable 17–20 litre tank, to be emptied every 2–3 days at a dedicated disposal point — never into a storm drain or into nature.
Where to fill and drain
Service points exist precisely for this: water and disposal stations, often €2–5 for a full fresh tank, found by the thousand in France, Germany and Italy. Campsites provide the service to guests, and many allow it for a few euros without an overnight stay. Community apps map water points; our stopovers guide walks through the full ritual — in order: cassette, grey water, then rinse and fill fresh, using the van's own hose.
Lasting 3 days on 100 litres
As a couple, 100 litres last a weekend in normal mode, three to four days in economy mode:
- Navy shower: wet, water off, soap, rinse — 5–8 litres instead of 30.
- Wash up in two basins rather than under running water; wipe grease off with paper first.
- Keep the mixer tap parked on cold so you don't fire up the boiler for nothing.
Rookie mistakes
Driving with full tanks at all times (120 useless kilos that show up at the pump), confusing the cassette-rinsing tap with the drinking-water tap (read the signage!), and returning the vehicle with a full cassette — most contracts charge €50–150 if it isn't emptied. All of this is worth checking at pickup: our departure checklist devotes a full chapter to the water circuit.