**Contents**show

Static pressure is measured when water is not flowing from a cap gauge attached to a fire hydrant. Residual pressure is measured from the same cap gauge while water is flowing. Gallons per minute is measured by a diffuser with a pitot and a GPM gauge while the hydrant is flowing.

## What is the pressure of a fire hydrant?

Fire hydrants are flow-tested at a residual pressure of 20 psi; therefore, firefighters should understand the typical flow rates of fire hydrants at that pressure.

## How do you calculate hydrant flow rate?

In other words, if your pitot pressure is 28 psi and your orifice size is 4, your theoretical discharge according to the table is 2,526 GPM. If the coefficient of your hydrant outlet is 0.9, multiplying 2,526 x 0.9 finds the actual rate of flow: 2,273.4 GPM.

## How do you calculate psi from gallons per minute?

To calculate GPM from pressure in PSI for water, follow these steps:

- Measure the pressure inside the tank using a pressure gauge.
- Subtract the atmospheric pressure from the tank pressure.
- Multiply the result from step 2 by 2 and divide by the density of water.

## How do you calculate flow rate from pressure?

Flow rate formula

There are two main approaches to calculating the flow rate Q which is equivalent to the difference in volume divided by the difference in time (Δv / Δt). The first one is if we know the pressure difference (pressure drop) between the two points for which we want to estimate the flow.

## How does PSI affect GPM?

The PSI refers to the amount of pressure produced and GPM refers to the amount of water flow. … PSI (Pounds per Square Inch) refers to the amount of cleaning pressure the machine can produce. GPM (Gallons per Minute) is the amount of water that is coming from the machine.

## How do I calculate flow rate?

To calculate the drops per minute, the drop factor is needed. The formula for calculating the IV flow rate (drip rate) is total volume (in mL) divided by time (in min), multiplied by the drop factor (in gtts/mL), which equals the IV flow rate in gtts/min.

## How do I calculate GPM?

The formula to find GPM is 60 divided by the seconds it takes to fill a one gallon container (60 / seconds = GPM). Example: The one gallon container fills in 5 seconds. 60 / 5 = 12 GPM. (60 divided by 5 equals 12 gallons per minute.)

## How do you calculate gpm for a fire hose?

What is the formula for gpm? For example, a one-inch smooth bore tip will have a discharge of 210 gpm: 29.72 × 12 × 7.07 = 210 gpm.