I made this manometer for a visual monitor to let me know if my dust collector filter needed cleaning. A manometer shows a difference is pressure between two points.This shows when there is pressure building up in the air filter as the filter gets plugged up with dust.
It is very critical where the air tube is sensing the pressure. On my system, the optimum point was at the top center of the filter.
I used a 3/8” ID clear tube with a ½” pipe thread adapter to install it in the top of the filter. Being able to hold the locknut deep inside the filter could be a challenge. Fortunately a 1 1/16” socket fit perfectly on the ½” locknut to tighten the adapter down.
I used a ½” box core router bit to form a groove in a board, to glue the tubing in. I used some colored lamp oil to fill the u-shaped tube so that I wouldn’t have to worry about the liquid evaporating. When the air filter becomes plugged, the air being forced into the filter by the 2 hp blower, puts pressure into the 3/8” tube. This is apparent when the colored lamp oil begins to rise on the left side. Cleaning the filter will balance the oil level back down.