I’d rather a pressure low / pressure high limit. I think that if you could program in a system back pressure per zone then if the pressure was below this point you have a pipe break. Above this you have a blockage. But it would get complicated due to tolerances required and what if your incoming pressure fluctuates beyond your pressure reducing valve (if fitted) anyway thats what I’ve been thinking of putting into mine. Could also be done via “if flow exceeds value” but I have a few pressure sensors and I dont have a flow meter….