Which type of pressure is present in the water system before water flows from the hydrant?

The presence of static pressure in a water system refers to the pressure present in the system when the water is not in motion. This type of pressure exists in the hydrant and the connected piping when no water is flowing, meaning it is a measure of the potential energy per unit volume of water. Static pressure is crucial as it determines the amount of pressure available to push water out of the hydrant when it is opened.

When firefighters connect to a hydrant, they rely on this static pressure to ensure there is enough energy to move the water flow through the hoses and into the fire situation. Once water starts moving, static pressure is converted into dynamic pressure, which is related to the flow of water. Understanding the difference between these pressures is vital for effective firefighting operations and ensures that crews can predict how much water they can expect when engaging with hydrants.