In order to determine that a plumbing system is free of leaks, it is common to attach a test instrument to a nipple later to be connected to the gas or water meter. The instrument includes a cap for mounting on the nipple, a one way valve, such as a conventional tire valve, for admission of fluid under pressure into the line and a pressure gauge for detecting any drop in pressure The system is charged with compressed air to a certain noted pressure and permitted to stand for a relatively long period of time during which time the gauge is unattended and exposed to usual hazards of a construction job. It has been common to use a Bourdon type gauge, complete with glass face plate. Such gauges tend to collect wet plaster and other debris. Often the gauge faces in the wrong direction. Reading the gauge is often cumbersome. Furthermore, it is not uncommon for such gauges to be broken deliberately or by accident.
The primary object of the present invention is to provide an improved test instrument for plumbing lines.