Quick answer
Gravity filling meters product by time, valve or level under gravity and can suit thin free-flowing liquids. Overflow filling fills to a consistent visual level by returning excess product, which can compensate for internal bottle-volume variation. Decide whether the commercial requirement is measured quantity or equal appearance.
Side-by-side comparison
| Decision factor | Gravity filling | Overflow level filling |
|---|---|---|
| Primary result | Controlled flow or dose | Consistent liquid height |
| Bottle variation | Equal doses may show different levels | Return flow compensates for internal volume differences |
| Product | Thin, free-flowing, non-problematic liquids | Usually thin liquids compatible with recirculation |
| Return product | Not inherently required | Excess is returned to the supply system |
| Foam | Controlled by nozzle and flow profile | Return and seal at neck require foam assessment |
| Container neck | Normal nozzle access | Requires suitable neck seal and geometry |
| Accuracy basis | Time, valve, volume or system design | Visual level; actual volume varies with container |
| Cleaning | Supply, tank, valves and nozzles | Also includes return circuit and overflow nozzles |
Decision checks
- Declared quantity and appearance requirement
- Internal bottle-volume variation
- Neck finish and overflow-nozzle seal
- Product compatibility with recirculation
- Foam and aeration behaviour
- Return-tank and cleaning design
- Required output and changeover range
How to prove the choice
Fill containers from several mould or supplier batches. Weigh doses and compare liquid height so the difference between quantity control and visual level is understood.
Relevant specialist route
View the solutionliquidfillers.co.ukLiquid Fillers
Liquid-filling routes for thin, foamy and specialist products.
Selection note: Do not select from a comparison table alone. Test representative product and packaging against a written acceptance plan.