Users can tell that a water pressure switch needs to be changed either judging by its age, whether or not the switch has sustained damage or not, or most importantly, if the switch responds to changes in water pressure. Pressure switches need replacement when they don't respond to pressure.
The water pressure switch helps maintain water pressure in your house by activating a water pump when water pressure dips below the level needed to maintain consistent pressure throughout a water system. The main reason water pressure switches require replacement is when they fail to act on changes in water pressure, and thus fail to turn on the water pump.
Users can directly test water pressure switches by measuring the water pressure before it passes the pressure switch. When the pressure drops, the user can then see if the switch activates the water pump. The pressure switch needs replacement if the pump turns on inconsistently.
Pressure switches also have an average lifespan, often estimated by the manufacturer and sometimes marked on the labeling of the switch. If a user suspects a switch may need replacement, they should consult the labeling and change the switch out if it is approaching or has surpassed its lifespan.