Custom GPM Leak Alerts

My sprinkler system in my yard puts out approximately 15 gpm according to the stream labs monitor. If I get a major leak on a water line outside the amount will increase to about 18 gpm. I can simulate this by opening a tap outside which I have done. Last year a line broke while I was on holidays and luckily my neighbor caught it and got the water shut off. I would like to set leak alerts with amounts higher than 6 gpm which the monitor currently has.