Using the 10-15-25 (percentage) rule, calculate the available water for a static pressure of 25 PSI and a residual pressure of 20 PSI while flowing 300 gallons.

To determine the available water using the 10-15-25 rule, one must first understand how this principle operates in relation to static and residual pressure while also considering the flow being measured. The 10-15-25 rule assists in estimating the maximum flow available from a hydrant or water supply, based on the relationship between static and residual pressures.

In this situation, the static pressure is 25 PSI and the residual pressure while flowing is 20 PSI. According to the 10-15-25 rule, the difference between the static and residual pressures can provide insight into how much additional water might be available for pumping. The flow being measured is 300 gallons.

First, calculate the difference between static and residual pressures:

• Static pressure: 25 PSI
• Residual pressure: 20 PSI
• Difference: 25 PSI - 20 PSI = 5 PSI

Next, apply the 10-15-25 rule. This rule indicates that for every 10 gallons of flow, there should be a 5 PSI drop in pressure (corresponding to the residual pressure). To find the total available water, we can inversely use the percentage of available flow and factor in the current 300 gallons being utilized.