Autolevel Bottle Cap

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Autolevel Bottle Cap
Autolevel cap.png
Modality Reinforcement
Schematic Type 3D CAD
Description Cap for 1L Nalgene bottle that dispenses water with constant force despite bottle level
Creator Jonny Saunders
Version 1
Date 2021-08-03
Git Hash f4018b8
Used In: Multi-Box Gravity-Fed Reward Delivery

Other Files

Attaches to the top of a Nalgene 1L Bottle and terminates in a Female Luer Lock.

Intended to be used with 1L Bottle Wall Mount to hold it upside down, it keeps a constant water pressure as the bottle drains.

The principle is that

  • as the water leaves the center tube, it fills up the reservoir of the cap until the water level seals the tube.
  • because air can't get in through the tube, the bottle comes to an equilibrium between the vaccum pressure in the sealed bottle and gravity. It releases no more water, and the water pressure that would come from the water in the tube and bottle is neutralized.
  • as the outer reservoir is drained, eventually it falls below the level of the tube, allowing air in, which returns us to the beginning of the cycle.

Here's a video of it in action:

We use it to provide water to 10 behavior boxes with 30 total water ports, taking advantage of the hardware.gpio.Solenoid class's calibration feature to be able to deliver predictable quantities of water despite variation in the water pressure experienced by the valve.

Fabrication Notes


The spout piece makes a suction area when it prints the threads that connect to the siphon piece, so it should be printed at an angle, 45 works.