What might an increase in vacuum while drafting indicate?

An increase in vacuum while drafting typically indicates that there is an obstruction in the water supply path, which can be caused by a clogged strainer. When the strainer becomes blocked with debris, it restricts the flow of water into the pump, resulting in an increased vacuum reading. This increased vacuum measures the pressure difference created by the pump trying to draw water in against the restriction caused by the clog.

The situation would not relate to an open valve, as opening a valve would typically allow for greater water flow and thus a decrease in vacuum. Insufficient water supply could manifest in different ways, such as low flow or no flow, but not necessarily as an increase in vacuum without other factors. Incorrect hose size may lead to issues with flow and pressure, but it would not specifically cause a rise in vacuum in the context of the drafting process.

Therefore, observing an increase in vacuum is a clear indicator of a clogged strainer that needs to be addressed to restore proper water flow.