Fire pump free flowing test - water waste calculation

[WaterSaver]

A fire pump system is being exercised for 10 minutes weekly by free flowing the water. The outlet size is 8" and the discharge pressure of the pump as 180psi. Per NFPA the test procedure could instead be recirculating the water. What is the formula for calculating the amount of water being wasted? I can provide additional variables if they're important to the calculation, please let me know.

 

[PEDARRIN2]

If you are doing the required NFPA testing, the highest flow rate would be 150% of the rated flow of the system.

If you are not performing the required test, i would take the rated pump flow rate x the amount of time. This would be the lowest amount of water you should expect. if you want to know the exact amount, you would have to calculate the pressure loss of the system and look at the pump flow curve.

That is the amount of water you should plan for.