Vertical tube manometers, U-tubes, or water column meters, are devices used to measure pressure. These are simple instruments that can be made at home and used to measure pressure in either water piping, or more commonly, HVAC systems. Increases and decreases in the level of water in the tubes of a manometer help to tell us what is happening with pressures that are not easily understood without such instrumentation. Fortunately, you can make your own manometer with commonly found materials at your local hardware store.
Attach the plastic tube to your board using the mounting clips. It should be oriented with both ends facing upward and the bend facing downward, looking like a 'U' shape.
Fill the tube with enough water that it is half full when sitting upright. Measure the amount used to fill the tube to aid in your pressure calculations.
Mount a piece of paper behind the tube and, using a ruler, mark increments on it with the zero mark indicating where the water level sits. Be sure to mark increments both above and below the water mark to allow for measurements of both positive and negative pressures.
Connect one end of the tube directly to the board, uncapped. Leave the other end of the tube loose, with enough slack to allow you to connect it to ductwork or piping to allow for testing.