Using the 10-20-30 rule, what is the available water in gallons for a static pressure of 55 PSI and a residual pressure of 43 PSI while flowing 800 gallons?

To determine the available water in gallons using the 10-20-30 rule, you first need to understand how this rule applies to calculating available water supply from a fire hydrant. The 10-20-30 rule states that if the static pressure is above 20 psi and the residual pressure is above 10 psi, there is enough flow to ensure adequate water supply for firefighting.

In this scenario, the static pressure is 55 PSI, and the residual pressure is 43 PSI while flowing 800 gallons. Here’s how it works:

1. Determining Pressure Difference: The difference between the static and residual pressures is calculated as follows:

   • Static Pressure: 55 PSI
   • Residual Pressure: 43 PSI
   • Pressure Lost: 55 PSI - 43 PSI = 12 PSI

2. Interpreting the 10-20-30 Rule: According to the rule, if the residual pressure drops down to 20 PSI while flowing, the available water supply can be estimated. The assumption is that a flow rate that maintains residual pressure above 20 PSI indicates a sustainable supply.

3. Calculating Available Water: When flowing 800 gallons at a flow pressure that