Bottom Fill – What is it in Vaping?

Definition

Bottom Fill is a tank-refilling method in which e-liquid is poured into a vape atomiser through a port located at the base of the tank, rather than the top. Found on many Mod“>Box Mod compatible clearomisers and rebuildable tanks, its purpose is to reduce leakage, simplify coil changes, and maintain a low profile when the device is stood upright. By accessing the fill port from below, vapers can keep the mouthpiece clean and avoid accidental spills, making it a beginner-friendly alternative to top-fill systems.

Technical Details

How Bottom Fill Works

Bottom-fill tanks use a threaded or sliding base cap that, when unscrewed or shifted, exposes one or two kidney-shaped fill ports (typically 6 mm × 4 mm). Silicone or nitrile gaskets surround the ports to create a vacuum seal when the cap is re-tightened, preventing seepage into the Battery compartment. The Bottom Coil or Vertical Coil)”>BVC (Bottom Vertical Coil) remains in place during filling, eliminating the need to remove the atomiser head each time. Variations include:

  • Quarter-turn bayonet bases – faster access, common on modern sub-ohm tanks.
  • Slide-to-fill – a spring-loaded plate that exposes the port with a sideways push.
  • Screw-off base – traditional threaded ring requiring 3–4 full rotations.

Usage & Tips

  • Prime before closing: After filling, invert the tank for 30 seconds to saturate the Deck“>Build Deck and coil, preventing dry hits.
  • Avoid over-tightening: Snug is enough; excess torque can deform the gasket and cause leaks.
  • Close airflow: Shut the AFC (air-flow-control) ring before opening the base to reduce pressure changes.
  • Common problem: E-liquid in the 510 pin. Solution: wipe the contact with a tissue and ensure the coil is fully seated.
  • Safety: Always power off the Box Mod when detaching the tank to prevent accidental firing.

History & Context

Bottom-fill tanks emerged in 2012 with early clearomisers like the Kanger EVOD, offering a leak-proof evolution from top-wick designs. As Australian vapers demanded higher wattage and larger Juice Capacity”>juice capacity, manufacturers refined gaskets and introduced tool-free bayonet systems, yet the core principle remains unchanged—simplicity at the base.

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