Holding tanks
Water System
Holding tanks, RV water tanks, fresh / grey / black tanks, waste tanks, RV holding tank system
Holding tanks is the umbrella term for an RV's onboard water tanks: the fresh-water tank, the grey-water tank (sink/shower), and the black-water tank (toilet). Tank levels are usually shown on a dash or wall-mounted monitor panel.
Typical US sizes: fresh 30–100 gal (110–380 L), grey 25–80 gal, black 20–50 gal. In Europe, fresh is usually 80–120 L, grey 70–100 L, and the black side is a 18–22 L cassette. Dumped at dump stations or motorhome service points. Below about −5 °C, tanks must be drained or heated to avoid cracks. Grey fills up nearly as fast as fresh empties — plan boondocking time around it.