A manometer is an instrument for measuring pressure. Plumbing used to control the pressure in the pipes, as low pressure can indicate an undesirable leak. At its simplest a manometer consists of a U-shaped tube filled with water or mercury. The pressure in the tube to which the manometer is connected causes the liquid in the tube. The distance that moves is proportional to the pressure. For safety reasons, the poisonous Mercury is replaced by a much safer digital sensor and a silicone rubber “connector tube” in modern manometers.
- Locate the point test on the tube, or a value that opens to the atmosphere, such as a gas burner or a faucet. Test points vary in size and shape, but generally consist of a clogged section of the pipe extending from the main pipe. For example, the test point of a refrigerant gas pipeline may be a 1/8-inch plugged pipe.
- Remove the plug from the end of the test point, if applicable, then push the rubber cone into the end of the pressure gauge tube, at the end of the value point or pipe test. Connection methods vary so consult the manufacturer of the manual before using.
- Make sure the pressure gauge is firmly sealed to the pipe. Open the tap, if present, to complete the connection between the manometer and the pipe. Stay with the manometer and observe the reading on the dial or show. This shows the pressure in the pipe.
- Close the tap, if open and then remove the pressure gauge from the pipe. Place the plug on the end of the test tube and make sure it is safe.
Tips and warnings
- Test points in tubes come in a variety of shapes and sizes, including in-line taps and models with what looks like a screw screwed into the end of a narrow tube.
- Take several reading check average results. The pressure is forced to vary throughout the day.
- The manometer in its case protects against damage and extends its useful life.
- Never leave an unattended gauge connected to a pipe. Most connections are based on a “push fit” system that can work loose without notice.
- Pressure gauges are precision instruments. Releasing them and exposing them to violent shocks can damage and reduce their accuracy.