Which type of valve is commonly used on private water supply systems and the words open or shut appear in a window as the valve approaches one position or the other?

Post indicator valves

Explanation:

Post indicator valves were first made and patented by its inventors Crookham and Lee in 1972 for Clow Corp., a pipe manufacturing company. In 1974, they were publicly installed for the first time.

PIV, indicator post, I post, IP, post indicator, or wall post, a post indicator valve is a valve assembly used for the purpose of underground piping for water supply to fire protection systems such as sprinklers, sprays, foams, deluges, etc. They have a lockable actuator which looks like a red metal steering wheel or a wrench/handle on top of a post. It consists of a glass or plastic window, which indicates whether the valve is open or shut.

PIVs can be of 3 types:

Ground Post: This is an indicator post that has its base buried in the ground and typically has a lockable handle or clamp. It is used when the valve is installed out of the building.

Wall Post: This is a short indicator post, usually horizontally bound through a flange to the wall of the building. This post can be operated by a handwheel.

Wall Post: This is a short indicator post, usually bolted horizontally to the wall of the building through a flange. This post is operated through a handwheel. This is used when the water supply passes through a cavity of the wall.

Pedestal Post: This post looks like a ground sign. Furthermore, instead of being embedded in the earth, it is bolted through a flange to a horizontal surface, usually a concrete base. It also operates through a handle or wrench that can be locked. It is helpful when the valve is situated inside a building and the water supply is stored