Pump Operations
Rated Capacity
Rated capacity is the flow a pump is rated to deliver at a reference pressure from draft, the headline number that describes how big the pump is. A pump moving water at its rated pressure is working at the top of what it was built to do.
The rating pairs a flow with a pressure: a pump is described by how much water it can move while holding a benchmark pressure, drafting from a modest lift. It is a way to compare pumps and to know what a given apparatus can be asked to supply.
Pushing a pump toward its rated flow uses up its pressure headroom — there is little left above the curve. Knowing the rating tells the operator when a demand, like a big master stream or several lines at once, is approaching what one pump can carry before a second engine is needed.