Bottle top dispensers can be classified depending upon the piston mechanism:
- Bottle top dispenser with floating piston
Such a system does not require any piston seal which makes it highly durable and easy to maintain due to low frictional wear. A floating piston fits into the dispensing cylinder without contacting the surface.This means that the piston and dispensing cylinder are separated by a gap (a few thousand of a millimeter wide).
- Bottle Top Dispenser with wiping-seal piston:
This type of bottle top dispenser features a wiping-seal in addition to a floating piston system. Dispensers that wield the sealed piston during the process of liquid transfer typically require high operating force. This is responsible for defective sealing due to friction wear and tear. To eliminate high operating forces during liquid filling, some systems use a spring with an automatic lifting action that minimizes friction.