What is the minimum allowable pressure in the distribution system under emergency conditions?

The minimum allowable pressure in a water distribution system under emergency conditions is important for ensuring adequate water delivery and maintaining system integrity. A pressure of 20 psi is typically seen as the threshold where sufficient flow can be provided for basic needs, such as fire protection and domestic use.

Maintaining a minimum pressure of 20 psi ensures that there is enough pressure to deliver water from hydrants or other sources during emergencies, which is crucial for firefighting and maintaining public health standards. Below this pressure, the risk of backflow and contamination increases, and the ability to maintain adequate service is compromised.

In contrast, values lower than 20 psi compromise the entire system's reliability and safety. A pressure lower than this may not support essential operational requirements during emergencies, hence, making 20 psi the minimum acceptable level.