Pick the Right Ball Nose Spring Plunger for You
The inner piece is hollow with a hole in the center, and the outer piece is solid around the hole with a smaller threaded center to accept either a rubber stopper or an airlock. In use, water is filled into the ball nose spring plunger until it reaches the top of the inner tubular chamber. Next, an appropriately-sized hole is drilled through both pieces from one side so that it lines up over this chamber when they are rotated closed by hand. A short length of plastic tubing is then pushed into this hole, which makes it possible to fill or drain air from below without disassembling the plunger.
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