I'm looking to find the gallons per minute lost during a water main break. The information I have is this. 8 inch lined cast iron pipe. System pressure is 84psi. c-factor for the pipe is 100. The pipe was broken with a gap completely around the pipe of 1/4 of an inch. Gound cover is 4.5 feet deep with asphalt on top of 3 inches. Water was escaping into the shell rock ground with no water visiable at the surface. This was a real water main break recently. If there is any other information that would someone would need I'm sure I can get it. What formula or considerations should be thought about when trying to find the GPM's for a water main break? Thank you for any help you can give.