This video describes how to make a simple low pressure regulator using a piece of tubing and a container of water. Hopefully, this video will spark an idea that could prove useful where traditional spring loaded or electrically actuated low pressure regulators are in short supply.
The theory is that when the pressure of the air is greater than the height of the water column, the excess air will spill from the submerged end of the tube and escape harmlessly to atmosphere. The height that determines this pressure setpoint is from the top of the container of water to the end of the submerged tube. The overall height of the container of water is not relevant.
The video shows the accuracy of this low pressure regulator as well within one inch of water column pressure. Also tested, but not shown in the video, is that the regulator maintains accuracy across a wide range of flow rates.
For more advanced concepts and ideas for ventilator components, visit this page