Gravity fill
Gravity water fill, open fill port, fresh water gravity fill, fill from jerry can, garden hose fill (no pressure)
Gravity fill is a fresh water tank port with an open funnel into which water can be poured from a jerry can, bucket, or garden hose without pressure. The alternative is a city water inlet, which connects to a pressurised mains tap.
Most motorhomes have either both systems (gravity fill + city water inlet) or only one. European campervans typically have a simple screw-off tank cap; American RVs have a separate hatch labelled "Fresh Water". Important: only use potable water through a food-safe (white) drinking hose — not a green garden hose.